From ff29664c28c91903f16f8bc9933d2962db648f61 Mon Sep 17 00:00:00 2001
From: Kasper Lund <kasper@toit.io>
Date: Fri, 13 Jan 2023 15:12:56 +0100
Subject: [PATCH] Record input types for loads and invokes in type propagator
 (#1339)

* Track input types for calls

* Simplify

* Allow block types
---
 src/compiler/propagation/type_database.cc     |  53 +-
 src/compiler/propagation/type_database.h      |  10 +-
 src/compiler/propagation/type_propagator.cc   |  60 +-
 src/compiler/propagation/type_propagator.h    |  11 +-
 src/compiler/propagation/type_stack.h         |   2 +
 src/compiler/propagation/type_variable.cc     |   2 +-
 .../type_propagation/gold/array_do_test.gold  |   8 +-
 .../gold/array_do_test.gold-O2                |   8 +-
 tests/type_propagation/gold/block_test.gold   | 120 +--
 .../type_propagation/gold/block_test.gold-O2  | 120 +--
 .../type_propagation/gold/deltablue_test.gold | 716 +++++++++---------
 .../gold/deltablue_test.gold-O2               | 716 +++++++++---------
 tests/type_propagation/gold/field_test.gold   |  26 +-
 .../type_propagation/gold/field_test.gold-O2  |  26 +-
 tests/type_propagation/gold/finally_test.gold |  38 +-
 .../gold/finally_test.gold-O2                 |  38 +-
 tests/type_propagation/gold/global_test.gold  |   8 +-
 .../type_propagation/gold/global_test.gold-O2 |   8 +-
 tests/type_propagation/gold/lambda_test.gold  |  24 +-
 .../type_propagation/gold/lambda_test.gold-O2 |  24 +-
 tests/type_propagation/gold/literal_test.gold |   2 +-
 .../gold/literal_test.gold-O2                 |   2 +-
 tests/type_propagation/gold/local_test.gold   |  52 +-
 .../type_propagation/gold/local_test.gold-O2  |  52 +-
 tests/type_propagation/gold/map_test.gold     |   6 +-
 tests/type_propagation/gold/map_test.gold-O2  |   6 +-
 tests/type_propagation/gold/nlr_test.gold     |  18 +-
 tests/type_propagation/gold/nlr_test.gold-O2  |  18 +-
 .../gold/non_local_branch_test.gold           |  18 +-
 .../gold/non_local_branch_test.gold-O2        |  18 +-
 .../gold/non_local_return_test.gold           |  12 +-
 .../gold/non_local_return_test.gold-O2        |  12 +-
 .../gold/null_equals_test.gold                |  56 +-
 .../gold/null_equals_test.gold-O2             |  56 +-
 .../type_propagation/gold/richards_test.gold  | 376 ++++-----
 .../gold/richards_test.gold-O2                | 376 ++++-----
 tests/type_propagation/gold/spawn_test.gold   |  10 +-
 .../type_propagation/gold/spawn_test.gold-O2  |  10 +-
 tests/type_propagation/gold/try_test.gold     |   4 +-
 tests/type_propagation/gold/try_test.gold-O2  |   4 +-
 .../type_propagation/gold/typecheck_test.gold |  30 +-
 .../gold/typecheck_test.gold-O2               |  30 +-
 tools/dump_types.toit                         |  14 +-
 43 files changed, 1636 insertions(+), 1564 deletions(-)

diff --git a/src/compiler/propagation/type_database.cc b/src/compiler/propagation/type_database.cc
index 41b7e7999..f62b6e9f5 100644
--- a/src/compiler/propagation/type_database.cc
+++ b/src/compiler/propagation/type_database.cc
@@ -45,9 +45,9 @@ TypeDatabase::~TypeDatabase() {
 
 void TypeDatabase::check_top(uint8* bcp, Object* value) const {
   int position = program_->absolute_bci_from_bcp(bcp);
-  auto probe = usage_.find(position);
-  if (probe == usage_.end()) {
-    FATAL("usage not analyzed: %d", position);
+  auto probe = output_.find(position);
+  if (probe == output_.end()) {
+    FATAL("output not analyzed: %d", position);
   }
   TypeSet type = probe->second;
   if (type.is_block()) {
@@ -159,9 +159,9 @@ const std::vector<TypeSet> TypeDatabase::arguments(Method method) const {
   return result;
 }
 
-const TypeSet TypeDatabase::usage(int position) const {
-  auto probe = usage_.find(position);
-  if (probe == usage_.end()) {
+const TypeSet TypeDatabase::output(int position) const {
+  auto probe = output_.find(position);
+  if (probe == output_.end()) {
     return TypeSet::invalid();
   } else {
     return probe->second;
@@ -209,15 +209,30 @@ std::string TypeDatabase::as_json() const {
   out << "[\n";
 
   bool first = true;
-  for (auto it : usage_) {
+  for (auto it : output_) {
     if (first) {
       first = false;
     } else {
       out << ",\n";
     }
-    std::string type_string = it.second.as_json(program_);
-    out << "  {\"position\": " << it.first;
-    out << ", \"type\": " << type_string << "}";
+
+    int position = it.first;
+    std::string output_string = it.second.as_json(program_);
+    out << "  {\"position\": " << position;
+    if (input_.find(position) != input_.end()) {
+      out << ", \"input\": [";
+      TypeStack* stack = input_.at(position);
+      for (int i = 0; i < stack->size(); i++) {
+        if (i != 0) {
+          out << ",";
+        }
+        TypeSet type = stack->get(i);
+        std::string type_string = type.as_json(program_);
+        out << type_string;
+      }
+      out << "]";
+    }
+    out << ", \"output\": " << output_string << "}";
   }
 
   for (auto it : methods_) {
@@ -263,11 +278,23 @@ void TypeDatabase::add_argument(Method method, int n, const TypeSet type) {
   arguments->set(n, type);
 }
 
-void TypeDatabase::add_usage(int position, const TypeSet type) {
-  ASSERT(usage_.find(position) == usage_.end());
+void TypeDatabase::add_input(int position, int n, int size, const TypeSet type) {
+  TypeStack* stack = null;
+  if (n == 0) {
+    ASSERT(input_.find(position) == input_.end());
+    stack = new TypeStack(size - 1, size, words_per_type_);
+    input_[position] = stack;
+  } else {
+    stack = input_.at(position);
+  }
+  stack->set(n, type);
+}
+
+void TypeDatabase::add_output(int position, const TypeSet type) {
+  ASSERT(output_.find(position) == output_.end());
   TypeSet copy = copy_type(type);
   uint8 opcode = *(program_->bcp_from_absolute_bci(position));
-  usage_.emplace(position, copy);
+  output_.emplace(position, copy);
   returns_.emplace(position + opcode_length[opcode], copy);
 }
 
diff --git a/src/compiler/propagation/type_database.h b/src/compiler/propagation/type_database.h
index cc5b2b86e..99ab4cb47 100644
--- a/src/compiler/propagation/type_database.h
+++ b/src/compiler/propagation/type_database.h
@@ -40,8 +40,7 @@ class TypeDatabase {
 
   const std::vector<Method> methods() const;
   const std::vector<TypeSet> arguments(Method method) const;
-  const TypeSet usage(int position) const;
-  const TypeSet return_type(int position) const;
+  const TypeSet output(int position) const;
 
   std::string as_json() const;
 
@@ -64,7 +63,9 @@ class TypeDatabase {
   std::vector<TypeStack*> types_;
 
   std::unordered_map<int, TypeStack*> methods_;
-  std::unordered_map<int, TypeSet> usage_;
+
+  std::unordered_map<int, TypeStack*> input_;
+  std::unordered_map<int, TypeSet> output_;
   std::unordered_map<int, TypeSet> returns_;
 
   static std::unordered_map<Program*, TypeDatabase*> cache_;
@@ -73,7 +74,8 @@ class TypeDatabase {
 
   void add_method(Method method);
   void add_argument(Method method, int n, const TypeSet type);
-  void add_usage(int position, const TypeSet type);
+  void add_input(int position, int n, int size, const TypeSet type);
+  void add_output(int position, const TypeSet type);
 
   TypeSet copy_type(const TypeSet type);
   TypeStack* add_types_block();
diff --git a/src/compiler/propagation/type_propagator.cc b/src/compiler/propagation/type_propagator.cc
index 883e31c01..2a7518e6f 100644
--- a/src/compiler/propagation/type_propagator.cc
+++ b/src/compiler/propagation/type_propagator.cc
@@ -259,16 +259,23 @@ void TypePropagator::propagate(TypeDatabase* types) {
     uint8* entry = program()->entry_task().entry();
     type.clear(words_per_type());
     type.add_instance(program()->task_class_id());
-    types->add_usage(program()->absolute_bci_from_bcp(entry), type);
+    types->add_output(program()->absolute_bci_from_bcp(entry), type);
   }
 
-  sites_.for_each([&](uint8* site, Set<TypeVariable*>& results) {
+  output_.for_each([&](uint8* site, Set<TypeVariable*>& output) {
     type.clear(words_per_type());
-    for (auto it = results.begin(); it != results.end(); it++) {
+    for (auto it = output.begin(); it != output.end(); it++) {
       type.add_all_also_blocks((*it)->type(), words_per_type());
     }
     int position = program()->absolute_bci_from_bcp(site);
-    types->add_usage(position, type);
+    types->add_output(position, type);
+  });
+
+  input_.for_each([&](uint8* site, std::vector<TypeVariable*>& variables) {
+    int position = program()->absolute_bci_from_bcp(site);
+    for (unsigned i = 0; i < variables.size(); i++) {
+      types->add_input(position, i, variables.size(), variables[i]->type());
+    }
   });
 
   // Group the methods and blocks based on the bytecode position, so
@@ -400,6 +407,7 @@ void TypePropagator::call_method(MethodTemplate* caller,
 void TypePropagator::call_static(MethodTemplate* caller, TypeScope* scope, uint8* site, Method target) {
   TypeStack* stack = scope->top();
   int arity = target.arity();
+  if (site) add_input(site, stack, arity);
 
   std::vector<ConcreteType> arguments;
   stack->push_empty();
@@ -470,6 +478,7 @@ void TypePropagator::call_static(MethodTemplate* caller, TypeScope* scope, uint8
 void TypePropagator::call_virtual(MethodTemplate* caller, TypeScope* scope, uint8* site, int arity, int offset) {
   TypeStack* stack = scope->top();
   TypeSet receiver = stack->local(arity - 1);
+  if (site) add_input(site, stack, arity);
 
   std::vector<ConcreteType> arguments;
   stack->push_empty();
@@ -501,6 +510,7 @@ void TypePropagator::call_block(TypeScope* scope, uint8* site, int arity) {
   TypeStack* stack = scope->top();
   TypeSet receiver = stack->local(arity - 1);
   BlockTemplate* block = receiver.block();
+  if (site) add_input(site, stack, arity);
 
   // If we're passing too few arguments to the block, this will
   // throw so we do not need to update the block's argument types.
@@ -568,8 +578,9 @@ void TypePropagator::load_lambda(TypeScope* scope, Method method) {
 
 void TypePropagator::load_field(MethodTemplate* user, TypeStack* stack, uint8* site, int index) {
   TypeSet instance = stack->local(0);
-  stack->push_empty();
+  if (site) add_input(site, stack, 1);
 
+  stack->push_empty();
   TypeSet::Iterator it(instance, words_per_type_);
   while (it.has_next()) {
     unsigned id = it.next();
@@ -603,7 +614,7 @@ void TypePropagator::load_outer(TypeScope* scope, uint8* site, int index) {
   // this particular access site. We use this merged type exclusively
   // for the output of the type propagator, so we don't actually
   // use the merged type anywhere in the analysis.
-  TypeVariable* merged = this->outer(site);
+  TypeVariable* merged = this->output(site);
   merged->type().add_all_also_blocks(value, words_per_type());
 }
 
@@ -623,7 +634,7 @@ bool TypePropagator::handle_typecheck_result(TypeScope* scope, uint8* site, bool
       scope->throw_maybe();
     }
   }
-  outer(site)->type().add_all(stack->local(0), words_per_type());
+  output(site)->type().add_all(stack->local(0), words_per_type());
   if (as_check) stack->pop();
   return can_succeed;
 }
@@ -657,13 +668,13 @@ TypeVariable* TypePropagator::global_variable(int index) {
   }
 }
 
-TypeVariable* TypePropagator::outer(uint8* site) {
+TypeVariable* TypePropagator::output(uint8* site) {
   auto it = outers_.find(site);
   if (it == outers_.end()) {
-    TypeVariable* variable = new TypeVariable(words_per_type());
-    outers_[site] = variable;
-    add_site(site, variable);
-    return variable;
+    TypeVariable* output = new TypeVariable(words_per_type());
+    outers_[site] = output;
+    add_output(site, output);
+    return output;
   } else {
     return it->second;
   }
@@ -675,8 +686,29 @@ void TypePropagator::enqueue(MethodTemplate* method) {
   enqueued_.push_back(method);
 }
 
-void TypePropagator::add_site(uint8* site, TypeVariable* result) {
-  sites_[site].insert(result);
+void TypePropagator::add_input(uint8* site, TypeStack* input, int n) {
+  auto probe = input_.find(site);
+  if (probe != input_.end()) {
+    std::vector<TypeVariable*>& variables = probe->second;
+    ASSERT(variables.size() == n);
+    for (int i = 0; i < n; i++) {
+      TypeVariable* variable = variables[i];
+      variable->type().add_all_also_blocks(input->local(n - i - 1), words_per_type());
+    }
+    return;
+  }
+
+  std::vector<TypeVariable*> variables;
+  for (int i = 0; i < n; i++) {
+    TypeVariable* variable = new TypeVariable(words_per_type());
+    variable->type().add_all_also_blocks(input->local(n - i - 1), words_per_type());
+    variables.push_back(variable);
+  }
+  input_[site] = variables;
+}
+
+void TypePropagator::add_output(uint8* site, TypeVariable* output) {
+  output_[site].insert(output);
 }
 
 MethodTemplate* TypePropagator::find_method(Method target, std::vector<ConcreteType> arguments) {
diff --git a/src/compiler/propagation/type_propagator.h b/src/compiler/propagation/type_propagator.h
index f699ed96c..25bb8e9ec 100644
--- a/src/compiler/propagation/type_propagator.h
+++ b/src/compiler/propagation/type_propagator.h
@@ -66,10 +66,12 @@ class TypePropagator {
 
   TypeVariable* global_variable(int index);
   TypeVariable* field(unsigned type, int index);
-  TypeVariable* outer(uint8* site);
+  TypeVariable* output(uint8* site);
 
   void enqueue(MethodTemplate* method);
-  void add_site(uint8* site, TypeVariable* result);
+
+  void add_input(uint8* site, TypeStack* input, int n);
+  void add_output(uint8* site, TypeVariable* output);
 
 #define ENSURE_ENTRY_POINT(name, symbol, arity) \
   void ensure_##name();
@@ -85,13 +87,14 @@ class TypePropagator {
   ENTRY_POINTS(HAS_ENTRY_POINT)
 #undef HAS_ENTRY_POINT
 
-  Map<uint8*, Set<TypeVariable*>> sites_;
+  Map<uint8*, std::vector<TypeVariable*>> input_;
+  Map<uint8*, Set<TypeVariable*>> output_;
 
   std::unordered_map<uint32, MethodTemplate*> methods_;
   std::unordered_map<uint32, BlockTemplate*> blocks_;
 
   std::unordered_map<int, TypeVariable*> globals_;
-  std::unordered_map<uint8*, TypeVariable*> outers_;
+  std::unordered_map<uint8*, TypeVariable*> outers_;  // TODO(kasper): Rename this.
   std::unordered_map<unsigned, std::unordered_map<int, TypeVariable*>> fields_;
   std::vector<MethodTemplate*> enqueued_;
 
diff --git a/src/compiler/propagation/type_stack.h b/src/compiler/propagation/type_stack.h
index e090282ee..e49248983 100644
--- a/src/compiler/propagation/type_stack.h
+++ b/src/compiler/propagation/type_stack.h
@@ -44,6 +44,8 @@ class TypeStack {
   }
 
   int sp() const { return sp_; }
+
+  int size() const { return size_; }
   int available() const { return size_ - (sp_ + 1); }
 
   TypeSet get(int index) {
diff --git a/src/compiler/propagation/type_variable.cc b/src/compiler/propagation/type_variable.cc
index 594d4787e..d07e4d484 100644
--- a/src/compiler/propagation/type_variable.cc
+++ b/src/compiler/propagation/type_variable.cc
@@ -20,7 +20,7 @@ namespace toit {
 namespace compiler {
 
 TypeSet TypeVariable::use(TypePropagator* propagator, MethodTemplate* user, uint8* site) {
-  if (site) propagator->add_site(site, this);
+  if (site) propagator->add_output(site, this);
   if (user) users_.insert(user);
   return type();
 }
diff --git a/tests/type_propagation/gold/array_do_test.gold b/tests/type_propagation/gold/array_do_test.gold
index 5d89c6cef..267d299b2 100644
--- a/tests/type_propagation/gold/array_do_test.gold
+++ b/tests/type_propagation/gold/array_do_test.gold
@@ -1,18 +1,18 @@
 main tests/type_propagation/array_do_test.toit
   0[025] - load smi 1
-  1[053] - invoke static create_array_ <sdk>/core/collections.toit // {LargeArray_|SmallArray_}
-  4[053] - invoke static create_list_literal_from_array_ <sdk>/core/collections.toit // {List_}
+  1[053] - invoke static create_array_ <sdk>/core/collections.toit // [{SmallInteger_}] -> {LargeArray_|SmallArray_}
+  4[053] - invoke static create_list_literal_from_array_ <sdk>/core/collections.toit // [{LargeArray_|SmallArray_}] -> {List_}
   7[029] - load [block] in main tests/type_propagation/array_do_test.toit
  12[015] - load local 1
  13[038] - load block 1
- 15[058] - invoke virtual do // {Null_}
+ 15[058] - invoke virtual do // [{List_}, [block]] -> {Null_}
  19[089] - return null S3 0
 
 [block] in main tests/type_propagation/array_do_test.toit
  - argument 0: [block]
  - argument 1: {*}
   0[016] - load local 2
-  1[053] - invoke static id tests/type_propagation/array_do_test.toit // {*}
+  1[053] - invoke static id tests/type_propagation/array_do_test.toit // [{*}] -> {*}
   4[088] - return S1 2
 
 id tests/type_propagation/array_do_test.toit
diff --git a/tests/type_propagation/gold/array_do_test.gold-O2 b/tests/type_propagation/gold/array_do_test.gold-O2
index 5d89c6cef..267d299b2 100644
--- a/tests/type_propagation/gold/array_do_test.gold-O2
+++ b/tests/type_propagation/gold/array_do_test.gold-O2
@@ -1,18 +1,18 @@
 main tests/type_propagation/array_do_test.toit
   0[025] - load smi 1
-  1[053] - invoke static create_array_ <sdk>/core/collections.toit // {LargeArray_|SmallArray_}
-  4[053] - invoke static create_list_literal_from_array_ <sdk>/core/collections.toit // {List_}
+  1[053] - invoke static create_array_ <sdk>/core/collections.toit // [{SmallInteger_}] -> {LargeArray_|SmallArray_}
+  4[053] - invoke static create_list_literal_from_array_ <sdk>/core/collections.toit // [{LargeArray_|SmallArray_}] -> {List_}
   7[029] - load [block] in main tests/type_propagation/array_do_test.toit
  12[015] - load local 1
  13[038] - load block 1
- 15[058] - invoke virtual do // {Null_}
+ 15[058] - invoke virtual do // [{List_}, [block]] -> {Null_}
  19[089] - return null S3 0
 
 [block] in main tests/type_propagation/array_do_test.toit
  - argument 0: [block]
  - argument 1: {*}
   0[016] - load local 2
-  1[053] - invoke static id tests/type_propagation/array_do_test.toit // {*}
+  1[053] - invoke static id tests/type_propagation/array_do_test.toit // [{*}] -> {*}
   4[088] - return S1 2
 
 id tests/type_propagation/array_do_test.toit
diff --git a/tests/type_propagation/gold/block_test.gold b/tests/type_propagation/gold/block_test.gold
index 5aabf06d8..60d08052a 100644
--- a/tests/type_propagation/gold/block_test.gold
+++ b/tests/type_propagation/gold/block_test.gold
@@ -23,10 +23,10 @@ test_simple tests/type_propagation/block_test.toit
   1[029] - load [block] in test_simple tests/type_propagation/block_test.toit
   6[025] - load smi 1
   7[038] - load block 1
-  9[058] - invoke virtual repeat // {Null_}
+  9[058] - invoke virtual repeat // [{SmallInteger_}, [block]] -> {Null_}
  13[041] - pop 1
  14[002] - pop, load local S0
- 16[053] - invoke static id tests/type_propagation/block_test.toit // {LargeInteger_|SmallInteger_}
+ 16[053] - invoke static id tests/type_propagation/block_test.toit // [{LargeInteger_|SmallInteger_}] -> {LargeInteger_|SmallInteger_}
  19[089] - return null S2 0
 
 [block] in test_simple tests/type_propagation/block_test.toit
@@ -35,29 +35,29 @@ test_simple tests/type_propagation/block_test.toit
   1[017] - load local 3
   2[005] - load outer S1 // {LargeInteger_|SmallInteger_}
   4[025] - load smi 1
-  5[073] - invoke add // {LargeInteger_|SmallInteger_}
+  5[073] - invoke add // [{LargeInteger_|SmallInteger_}, {SmallInteger_}] -> {LargeInteger_|SmallInteger_}
   6[006] - store outer S1
   8[088] - return S1 1
 
 test_invokes tests/type_propagation/block_test.toit
   0[029] - load [block] in test_invokes tests/type_propagation/block_test.toit
   5[038] - load block 0
-  7[053] - invoke static invoke tests/type_propagation/block_test.toit // {SmallInteger_}
+  7[053] - invoke static invoke tests/type_propagation/block_test.toit // [[block]] -> {SmallInteger_}
  10[040] - pop 2
  12[029] - load [block] in test_invokes tests/type_propagation/block_test.toit
  17[020] - load literal horse
  19[038] - load block 1
- 21[053] - invoke static invoke tests/type_propagation/block_test.toit // {String_}
+ 21[053] - invoke static invoke tests/type_propagation/block_test.toit // [{String_}, [block]] -> {String_}
  24[040] - pop 2
  26[029] - load [block] in test_invokes tests/type_propagation/block_test.toit
  31[026] - load smi 87
  33[038] - load block 1
- 35[053] - invoke static invoke tests/type_propagation/block_test.toit // {SmallInteger_}
+ 35[053] - invoke static invoke tests/type_propagation/block_test.toit // [{SmallInteger_}, [block]] -> {SmallInteger_}
  38[040] - pop 2
  40[029] - load [block] in test_invokes tests/type_propagation/block_test.toit
  45[020] - load literal true
  47[038] - load block 1
- 49[053] - invoke static invoke tests/type_propagation/block_test.toit // {True_}
+ 49[053] - invoke static invoke tests/type_propagation/block_test.toit // [{True_}, [block]] -> {True_}
  52[089] - return null S2 0
 
 [block] in test_invokes tests/type_propagation/block_test.toit
@@ -83,7 +83,7 @@ test_invokes tests/type_propagation/block_test.toit
   0[029] - load [block] in [block] in test_invokes tests/type_propagation/block_test.toit
   5[017] - load local 3
   6[038] - load block 1
-  8[053] - invoke static invoke tests/type_propagation/block_test.toit // {SmallInteger_}
+  8[053] - invoke static invoke tests/type_propagation/block_test.toit // [{SmallInteger_}, [block]] -> {SmallInteger_}
  11[004] - store local, pop S1
  13[088] - return S1 2
 
@@ -99,7 +99,7 @@ test_invokes tests/type_propagation/block_test.toit
   0[029] - load [block] in [block] in test_invokes tests/type_propagation/block_test.toit
   5[017] - load local 3
   6[038] - load block 1
-  8[053] - invoke static invoke tests/type_propagation/block_test.toit // {True_}
+  8[053] - invoke static invoke tests/type_propagation/block_test.toit // [{True_}, [block]] -> {True_}
  11[004] - store local, pop S1
  13[088] - return S1 2
 
@@ -107,18 +107,18 @@ test_nesting tests/type_propagation/block_test.toit
   0[022] - load null
   1[029] - load [block] in test_nesting tests/type_propagation/block_test.toit
   6[038] - load block 0
-  8[053] - invoke static invoke tests/type_propagation/block_test.toit // {String_|SmallInteger_}
+  8[053] - invoke static invoke tests/type_propagation/block_test.toit // [[block]] -> {String_|SmallInteger_}
  11[041] - pop 1
  12[002] - pop, load local S0
- 14[053] - invoke static id tests/type_propagation/block_test.toit // {String_|Null_|SmallInteger_}
+ 14[053] - invoke static id tests/type_propagation/block_test.toit // [{String_|Null_|SmallInteger_}] -> {String_|Null_|SmallInteger_}
  17[041] - pop 1
  18[022] - load null
  19[029] - load [block] in test_nesting tests/type_propagation/block_test.toit
  24[038] - load block 0
- 26[053] - invoke static invoke tests/type_propagation/block_test.toit // {Null_|True_|float}
+ 26[053] - invoke static invoke tests/type_propagation/block_test.toit // [[block]] -> {Null_|True_|float}
  29[041] - pop 1
  30[002] - pop, load local S0
- 32[053] - invoke static id tests/type_propagation/block_test.toit // {Null_|True_|float}
+ 32[053] - invoke static id tests/type_propagation/block_test.toit // [{Null_|True_|float}] -> {Null_|True_|float}
  35[089] - return null S3 0
 
 [block] in test_nesting tests/type_propagation/block_test.toit
@@ -136,18 +136,18 @@ test_nesting tests/type_propagation/block_test.toit
  20[041] - pop 1
  21[016] - load local 2
  22[005] - load outer S1 // {String_|SmallInteger_}
- 24[053] - invoke static id tests/type_propagation/block_test.toit // {String_|SmallInteger_}
+ 24[053] - invoke static id tests/type_propagation/block_test.toit // [{String_|SmallInteger_}] -> {String_|SmallInteger_}
  27[088] - return S1 1
 
 [block] in test_nesting tests/type_propagation/block_test.toit
  - argument 0: [block]
   0[029] - load [block] in [block] in test_nesting tests/type_propagation/block_test.toit
   5[038] - load block 0
-  7[053] - invoke static invoke tests/type_propagation/block_test.toit // {True_|float}
+  7[053] - invoke static invoke tests/type_propagation/block_test.toit // [[block]] -> {True_|float}
  10[041] - pop 1
  11[002] - pop, load local S2
  13[005] - load outer S1 // {Null_|True_|float}
- 15[053] - invoke static id tests/type_propagation/block_test.toit // {Null_|True_|float}
+ 15[053] - invoke static id tests/type_propagation/block_test.toit // [{Null_|True_|float}] -> {Null_|True_|float}
  18[088] - return S1 1
 
 [block] in [block] in test_nesting tests/type_propagation/block_test.toit
@@ -168,7 +168,7 @@ test_nesting tests/type_propagation/block_test.toit
  25[016] - load local 2
  26[005] - load outer S3 // [block]
  28[005] - load outer S1 // {True_|float}
- 30[053] - invoke static id tests/type_propagation/block_test.toit // {True_|float}
+ 30[053] - invoke static id tests/type_propagation/block_test.toit // [{True_|float}] -> {True_|float}
  33[088] - return S1 1
 
 test_catch tests/type_propagation/block_test.toit
@@ -176,7 +176,7 @@ test_catch tests/type_propagation/block_test.toit
   1[029] - load [block] in test_catch tests/type_propagation/block_test.toit
   6[094] - link try 0
   8[038] - load block 4
- 10[055] - invoke block S1 // {False_}
+ 10[055] - invoke block S1 // [[block]] -> {False_}
  12[041] - pop 1
  13[095] - unlink try 0
  15[096] - unwind
@@ -186,20 +186,20 @@ test_catch tests/type_propagation/block_test.toit
  23[038] - load block 0
  25[022] - load null
  26[022] - load null
- 27[053] - invoke static catch <sdk>/core/exceptions.toit // {*}
+ 27[053] - invoke static catch <sdk>/core/exceptions.toit // [[block], {Null_}, {Null_}] -> {*}
  30[041] - pop 1
  31[002] - pop, load local S0
- 33[053] - invoke static id tests/type_propagation/block_test.toit // {Null_|SmallInteger_}
+ 33[053] - invoke static id tests/type_propagation/block_test.toit // [{Null_|SmallInteger_}] -> {Null_|SmallInteger_}
  36[041] - pop 1
  37[022] - load null
  38[029] - load [block] in test_catch tests/type_propagation/block_test.toit
  43[038] - load block 0
  45[022] - load null
  46[022] - load null
- 47[053] - invoke static catch <sdk>/core/exceptions.toit // {*}
+ 47[053] - invoke static catch <sdk>/core/exceptions.toit // [[block], {Null_}, {Null_}] -> {*}
  50[041] - pop 1
  51[002] - pop, load local S0
- 53[053] - invoke static id tests/type_propagation/block_test.toit // {String_|Null_|float}
+ 53[053] - invoke static id tests/type_propagation/block_test.toit // [{String_|Null_|float}] -> {String_|Null_|float}
  56[089] - return null S4 0
 
 [block] in test_catch tests/type_propagation/block_test.toit
@@ -216,7 +216,7 @@ test_catch tests/type_propagation/block_test.toit
   3[006] - store outer S1
   5[041] - pop 1
   6[020] - load literal woops
-  8[053] - invoke static throw <sdk>/core/exceptions.toit // {}
+  8[053] - invoke static throw <sdk>/core/exceptions.toit // [{String_}] -> {}
  11[088] - return S1 1
 
 [block] in test_catch tests/type_propagation/block_test.toit
@@ -236,14 +236,14 @@ test_too_few_arguments tests/type_propagation/block_test.toit
   5[038] - load block 0
   7[022] - load null
   8[022] - load null
-  9[053] - invoke static catch <sdk>/core/exceptions.toit // {*}
+  9[053] - invoke static catch <sdk>/core/exceptions.toit // [[block], {Null_}, {Null_}] -> {*}
  12[089] - return null S2 0
 
 [block] in test_too_few_arguments tests/type_propagation/block_test.toit
  - argument 0: [block]
   0[029] - load [block] in [block] in test_too_few_arguments tests/type_propagation/block_test.toit
   5[038] - load block 0
-  7[053] - invoke static invoke tests/type_propagation/block_test.toit // {}
+  7[053] - invoke static invoke tests/type_propagation/block_test.toit // [[block]] -> {}
  10[040] - pop 2
  12[026] - load smi 42
  14[053] - invoke static id tests/type_propagation/block_test.toit
@@ -255,12 +255,12 @@ test_modify_outer tests/type_propagation/block_test.toit
   3[029] - load [block] in test_modify_outer tests/type_propagation/block_test.toit
   8[026] - load smi 2
  10[038] - load block 1
- 12[058] - invoke virtual repeat // {Null_}
+ 12[058] - invoke virtual repeat // [{SmallInteger_}, [block]] -> {Null_}
  16[041] - pop 1
  17[002] - pop, load local S1
- 19[053] - invoke static id tests/type_propagation/block_test.toit // {String_|SmallInteger_}
+ 19[053] - invoke static id tests/type_propagation/block_test.toit // [{String_|SmallInteger_}] -> {String_|SmallInteger_}
  22[002] - pop, load local S0
- 24[053] - invoke static id tests/type_propagation/block_test.toit // {String_|SmallInteger_}
+ 24[053] - invoke static id tests/type_propagation/block_test.toit // [{String_|SmallInteger_}] -> {String_|SmallInteger_}
  27[089] - return null S3 0
 
 [block] in test_modify_outer tests/type_propagation/block_test.toit
@@ -280,12 +280,12 @@ test_modify_outer_nested tests/type_propagation/block_test.toit
   3[029] - load [block] in test_modify_outer_nested tests/type_propagation/block_test.toit
   8[026] - load smi 2
  10[038] - load block 1
- 12[058] - invoke virtual repeat // {Null_}
+ 12[058] - invoke virtual repeat // [{SmallInteger_}, [block]] -> {Null_}
  16[041] - pop 1
  17[002] - pop, load local S1
- 19[053] - invoke static id tests/type_propagation/block_test.toit // {String_|SmallInteger_}
+ 19[053] - invoke static id tests/type_propagation/block_test.toit // [{String_|SmallInteger_}] -> {String_|SmallInteger_}
  22[002] - pop, load local S0
- 24[053] - invoke static id tests/type_propagation/block_test.toit // {String_|SmallInteger_}
+ 24[053] - invoke static id tests/type_propagation/block_test.toit // [{String_|SmallInteger_}] -> {String_|SmallInteger_}
  27[089] - return null S3 0
 
 [block] in test_modify_outer_nested tests/type_propagation/block_test.toit
@@ -293,14 +293,14 @@ test_modify_outer_nested tests/type_propagation/block_test.toit
   0[029] - load [block] in [block] in test_modify_outer_nested tests/type_propagation/block_test.toit
   5[026] - load smi 3
   7[038] - load block 1
-  9[058] - invoke virtual repeat // {Null_}
+  9[058] - invoke virtual repeat // [{SmallInteger_}, [block]] -> {Null_}
  13[041] - pop 1
  14[002] - pop, load local S2
  16[005] - load outer S2 // {String_|SmallInteger_}
- 18[053] - invoke static id tests/type_propagation/block_test.toit // {String_|SmallInteger_}
+ 18[053] - invoke static id tests/type_propagation/block_test.toit // [{String_|SmallInteger_}] -> {String_|SmallInteger_}
  21[002] - pop, load local S2
  23[005] - load outer S1 // {String_|SmallInteger_}
- 25[053] - invoke static id tests/type_propagation/block_test.toit // {String_|SmallInteger_}
+ 25[053] - invoke static id tests/type_propagation/block_test.toit // [{String_|SmallInteger_}] -> {String_|SmallInteger_}
  28[088] - return S1 1
 
 [block] in [block] in test_modify_outer_nested tests/type_propagation/block_test.toit
@@ -320,35 +320,35 @@ test_modify_outer_nested tests/type_propagation/block_test.toit
 test_recursion tests/type_propagation/block_test.toit
   0[029] - load [block] in test_recursion tests/type_propagation/block_test.toit
   5[038] - load block 0
-  7[053] - invoke static recursive_null tests/type_propagation/block_test.toit // {Null_|SmallInteger_}
+  7[053] - invoke static recursive_null tests/type_propagation/block_test.toit // [[block]] -> {Null_|SmallInteger_}
  10[040] - pop 2
  12[029] - load [block] in test_recursion tests/type_propagation/block_test.toit
  17[038] - load block 0
- 19[053] - invoke static recursive_null tests/type_propagation/block_test.toit // {Null_|False_}
+ 19[053] - invoke static recursive_null tests/type_propagation/block_test.toit // [[block]] -> {Null_|False_}
  22[040] - pop 2
  24[029] - load [block] in test_recursion tests/type_propagation/block_test.toit
  29[038] - load block 0
- 31[053] - invoke static recursive_call tests/type_propagation/block_test.toit // {SmallInteger_}
+ 31[053] - invoke static recursive_call tests/type_propagation/block_test.toit // [[block]] -> {SmallInteger_}
  34[040] - pop 2
  36[029] - load [block] in test_recursion tests/type_propagation/block_test.toit
  41[038] - load block 0
- 43[053] - invoke static recursive_call tests/type_propagation/block_test.toit // {True_}
+ 43[053] - invoke static recursive_call tests/type_propagation/block_test.toit // [[block]] -> {True_}
  46[040] - pop 2
  48[029] - load [block] in test_recursion tests/type_propagation/block_test.toit
  53[038] - load block 0
- 55[053] - invoke static recursive_a_null tests/type_propagation/block_test.toit // {Null_|SmallInteger_}
+ 55[053] - invoke static recursive_a_null tests/type_propagation/block_test.toit // [[block]] -> {Null_|SmallInteger_}
  58[040] - pop 2
  60[029] - load [block] in test_recursion tests/type_propagation/block_test.toit
  65[038] - load block 0
- 67[053] - invoke static recursive_a_null tests/type_propagation/block_test.toit // {String_|Null_}
+ 67[053] - invoke static recursive_a_null tests/type_propagation/block_test.toit // [[block]] -> {String_|Null_}
  70[040] - pop 2
  72[029] - load [block] in test_recursion tests/type_propagation/block_test.toit
  77[038] - load block 0
- 79[053] - invoke static recursive_a_call tests/type_propagation/block_test.toit // {SmallInteger_}
+ 79[053] - invoke static recursive_a_call tests/type_propagation/block_test.toit // [[block]] -> {SmallInteger_}
  82[040] - pop 2
  84[029] - load [block] in test_recursion tests/type_propagation/block_test.toit
  89[038] - load block 0
- 91[053] - invoke static recursive_a_call tests/type_propagation/block_test.toit // {String_}
+ 91[053] - invoke static recursive_a_call tests/type_propagation/block_test.toit // [[block]] -> {String_}
  94[089] - return null S2 0
 
 [block] in test_recursion tests/type_propagation/block_test.toit
@@ -394,15 +394,15 @@ test_recursion tests/type_propagation/block_test.toit
 test_dead tests/type_propagation/block_test.toit
   0[029] - load [block] in test_dead tests/type_propagation/block_test.toit
   5[038] - load block 0
-  7[053] - invoke static ignore tests/type_propagation/block_test.toit // {Null_}
+  7[053] - invoke static ignore tests/type_propagation/block_test.toit // [[block]] -> {Null_}
  10[040] - pop 2
  12[029] - load [block] in test_dead tests/type_propagation/block_test.toit
  17[038] - load block 0
- 19[053] - invoke static ignore tests/type_propagation/block_test.toit // {Null_}
+ 19[053] - invoke static ignore tests/type_propagation/block_test.toit // [[block]] -> {Null_}
  22[040] - pop 2
  24[029] - load [block] in test_dead tests/type_propagation/block_test.toit
  29[038] - load block 0
- 31[053] - invoke static ignore tests/type_propagation/block_test.toit // {Null_}
+ 31[053] - invoke static ignore tests/type_propagation/block_test.toit // [[block]] -> {Null_}
  34[089] - return null S2 0
 
 recursive_null tests/type_propagation/block_test.toit
@@ -411,11 +411,11 @@ recursive_null tests/type_propagation/block_test.toit
   3[082] - branch if false T21
   6[029] - load [block] in recursive_null tests/type_propagation/block_test.toit
  11[038] - load block 0
- 13[053] - invoke static recursive_null tests/type_propagation/block_test.toit // {Null_}
+ 13[053] - invoke static recursive_null tests/type_propagation/block_test.toit // [[block]] -> {Null_}
  16[004] - store local, pop S1
  18[088] - return S1 1
  21[016] - load local 2
- 22[055] - invoke block S1 // {Null_|False_|SmallInteger_}
+ 22[055] - invoke block S1 // [[block]] -> {Null_|False_|SmallInteger_}
  24[088] - return S1 1
 
 [block] in recursive_null tests/type_propagation/block_test.toit
@@ -428,10 +428,10 @@ recursive_call tests/type_propagation/block_test.toit
   0[053] - invoke static pick tests/type_propagation/block_test.toit // {True_|False_}
   3[082] - branch if false T13
   6[016] - load local 2
-  7[053] - invoke static recursive_call tests/type_propagation/block_test.toit // {True_|SmallInteger_}
+  7[053] - invoke static recursive_call tests/type_propagation/block_test.toit // [[block]] -> {True_|SmallInteger_}
  10[088] - return S1 1
  13[016] - load local 2
- 14[055] - invoke block S1 // {True_|SmallInteger_}
+ 14[055] - invoke block S1 // [[block]] -> {True_|SmallInteger_}
  16[088] - return S1 1
 
 recursive_a_null tests/type_propagation/block_test.toit
@@ -440,18 +440,18 @@ recursive_a_null tests/type_propagation/block_test.toit
   3[082] - branch if false T21
   6[029] - load [block] in recursive_a_null tests/type_propagation/block_test.toit
  11[038] - load block 0
- 13[053] - invoke static recursive_b_null tests/type_propagation/block_test.toit // {Null_}
+ 13[053] - invoke static recursive_b_null tests/type_propagation/block_test.toit // [[block]] -> {Null_}
  16[004] - store local, pop S1
  18[088] - return S1 1
  21[016] - load local 2
- 22[055] - invoke block S1 // {String_|Null_|SmallInteger_}
+ 22[055] - invoke block S1 // [[block]] -> {String_|Null_|SmallInteger_}
  24[088] - return S1 1
 
 recursive_b_null tests/type_propagation/block_test.toit
  - argument 0: [block]
   0[029] - load [block] in recursive_b_null tests/type_propagation/block_test.toit
   5[038] - load block 0
-  7[053] - invoke static recursive_a_null tests/type_propagation/block_test.toit // {Null_}
+  7[053] - invoke static recursive_a_null tests/type_propagation/block_test.toit // [[block]] -> {Null_}
  10[004] - store local, pop S1
  12[088] - return S1 1
 
@@ -465,23 +465,23 @@ recursive_a_call tests/type_propagation/block_test.toit
   0[053] - invoke static pick tests/type_propagation/block_test.toit // {True_|False_}
   3[082] - branch if false T13
   6[016] - load local 2
-  7[053] - invoke static recursive_b_call tests/type_propagation/block_test.toit // {String_|SmallInteger_}
+  7[053] - invoke static recursive_b_call tests/type_propagation/block_test.toit // [[block]] -> {String_|SmallInteger_}
  10[088] - return S1 1
  13[016] - load local 2
- 14[055] - invoke block S1 // {String_|SmallInteger_}
+ 14[055] - invoke block S1 // [[block]] -> {String_|SmallInteger_}
  16[088] - return S1 1
 
 recursive_b_call tests/type_propagation/block_test.toit
  - argument 0: [block]
   0[016] - load local 2
-  1[053] - invoke static recursive_a_call tests/type_propagation/block_test.toit // {String_|SmallInteger_}
+  1[053] - invoke static recursive_a_call tests/type_propagation/block_test.toit // [[block]] -> {String_|SmallInteger_}
   4[088] - return S1 1
 
 maybe_throw tests/type_propagation/block_test.toit
   0[053] - invoke static pick tests/type_propagation/block_test.toit // {True_|False_}
   3[082] - branch if false T12
   6[020] - load literal woops
-  8[053] - invoke static throw <sdk>/core/exceptions.toit // {}
+  8[053] - invoke static throw <sdk>/core/exceptions.toit // [{String_}] -> {}
  11[041] - pop 1
  12[089] - return null S0 0
 
@@ -496,15 +496,15 @@ ignore tests/type_propagation/block_test.toit
 
 pick tests/type_propagation/block_test.toit
   0[026] - load smi 100
-  2[053] - invoke static random <sdk>/core/utils.toit // {LargeInteger_|SmallInteger_}
+  2[053] - invoke static random <sdk>/core/utils.toit // [{SmallInteger_}] -> {LargeInteger_|SmallInteger_}
   5[026] - load smi 50
-  7[063] - invoke lt // {True_|False_}
+  7[063] - invoke lt // [{LargeInteger_|SmallInteger_}, {SmallInteger_}] -> {True_|False_}
   8[088] - return S1 0
 
 invoke tests/type_propagation/block_test.toit
  - argument 0: [block]
   0[016] - load local 2
-  1[055] - invoke block S1 // {String_|Null_|True_|float|SmallInteger_}
+  1[055] - invoke block S1 // [[block]] -> {String_|Null_|True_|float|SmallInteger_}
   3[088] - return S1 1
 
 invoke tests/type_propagation/block_test.toit
@@ -512,5 +512,5 @@ invoke tests/type_propagation/block_test.toit
  - argument 1: [block]
   0[016] - load local 2
   1[018] - load local 4
-  2[055] - invoke block S2 // {String_|True_|SmallInteger_}
+  2[055] - invoke block S2 // [[block], {String_|True_|SmallInteger_}] -> {String_|True_|SmallInteger_}
   4[088] - return S1 2
diff --git a/tests/type_propagation/gold/block_test.gold-O2 b/tests/type_propagation/gold/block_test.gold-O2
index ffc8069ab..5ca1ac8ed 100644
--- a/tests/type_propagation/gold/block_test.gold-O2
+++ b/tests/type_propagation/gold/block_test.gold-O2
@@ -23,10 +23,10 @@ test_simple tests/type_propagation/block_test.toit
   1[029] - load [block] in test_simple tests/type_propagation/block_test.toit
   6[025] - load smi 1
   7[038] - load block 1
-  9[058] - invoke virtual repeat // {Null_}
+  9[058] - invoke virtual repeat // [{SmallInteger_}, [block]] -> {Null_}
  13[041] - pop 1
  14[002] - pop, load local S0
- 16[053] - invoke static id tests/type_propagation/block_test.toit // {LargeInteger_|SmallInteger_}
+ 16[053] - invoke static id tests/type_propagation/block_test.toit // [{LargeInteger_|SmallInteger_}] -> {LargeInteger_|SmallInteger_}
  19[089] - return null S2 0
 
 [block] in test_simple tests/type_propagation/block_test.toit
@@ -35,29 +35,29 @@ test_simple tests/type_propagation/block_test.toit
   1[017] - load local 3
   2[005] - load outer S1 // {LargeInteger_|SmallInteger_}
   4[025] - load smi 1
-  5[073] - invoke add // {LargeInteger_|SmallInteger_}
+  5[073] - invoke add // [{LargeInteger_|SmallInteger_}, {SmallInteger_}] -> {LargeInteger_|SmallInteger_}
   6[006] - store outer S1
   8[088] - return S1 1
 
 test_invokes tests/type_propagation/block_test.toit
   0[029] - load [block] in test_invokes tests/type_propagation/block_test.toit
   5[038] - load block 0
-  7[053] - invoke static invoke tests/type_propagation/block_test.toit // {SmallInteger_}
+  7[053] - invoke static invoke tests/type_propagation/block_test.toit // [[block]] -> {SmallInteger_}
  10[040] - pop 2
  12[029] - load [block] in test_invokes tests/type_propagation/block_test.toit
  17[020] - load literal horse
  19[038] - load block 1
- 21[053] - invoke static invoke tests/type_propagation/block_test.toit // {String_}
+ 21[053] - invoke static invoke tests/type_propagation/block_test.toit // [{String_}, [block]] -> {String_}
  24[040] - pop 2
  26[029] - load [block] in test_invokes tests/type_propagation/block_test.toit
  31[026] - load smi 87
  33[038] - load block 1
- 35[053] - invoke static invoke tests/type_propagation/block_test.toit // {SmallInteger_}
+ 35[053] - invoke static invoke tests/type_propagation/block_test.toit // [{SmallInteger_}, [block]] -> {SmallInteger_}
  38[040] - pop 2
  40[029] - load [block] in test_invokes tests/type_propagation/block_test.toit
  45[020] - load literal true
  47[038] - load block 1
- 49[053] - invoke static invoke tests/type_propagation/block_test.toit // {True_}
+ 49[053] - invoke static invoke tests/type_propagation/block_test.toit // [{True_}, [block]] -> {True_}
  52[089] - return null S2 0
 
 [block] in test_invokes tests/type_propagation/block_test.toit
@@ -83,7 +83,7 @@ test_invokes tests/type_propagation/block_test.toit
   0[029] - load [block] in [block] in test_invokes tests/type_propagation/block_test.toit
   5[017] - load local 3
   6[038] - load block 1
-  8[053] - invoke static invoke tests/type_propagation/block_test.toit // {SmallInteger_}
+  8[053] - invoke static invoke tests/type_propagation/block_test.toit // [{SmallInteger_}, [block]] -> {SmallInteger_}
  11[004] - store local, pop S1
  13[088] - return S1 2
 
@@ -99,7 +99,7 @@ test_invokes tests/type_propagation/block_test.toit
   0[029] - load [block] in [block] in test_invokes tests/type_propagation/block_test.toit
   5[017] - load local 3
   6[038] - load block 1
-  8[053] - invoke static invoke tests/type_propagation/block_test.toit // {True_}
+  8[053] - invoke static invoke tests/type_propagation/block_test.toit // [{True_}, [block]] -> {True_}
  11[004] - store local, pop S1
  13[088] - return S1 2
 
@@ -107,18 +107,18 @@ test_nesting tests/type_propagation/block_test.toit
   0[022] - load null
   1[029] - load [block] in test_nesting tests/type_propagation/block_test.toit
   6[038] - load block 0
-  8[053] - invoke static invoke tests/type_propagation/block_test.toit // {String_|SmallInteger_}
+  8[053] - invoke static invoke tests/type_propagation/block_test.toit // [[block]] -> {String_|SmallInteger_}
  11[041] - pop 1
  12[002] - pop, load local S0
- 14[053] - invoke static id tests/type_propagation/block_test.toit // {String_|Null_|SmallInteger_}
+ 14[053] - invoke static id tests/type_propagation/block_test.toit // [{String_|Null_|SmallInteger_}] -> {String_|Null_|SmallInteger_}
  17[041] - pop 1
  18[022] - load null
  19[029] - load [block] in test_nesting tests/type_propagation/block_test.toit
  24[038] - load block 0
- 26[053] - invoke static invoke tests/type_propagation/block_test.toit // {Null_|True_|float}
+ 26[053] - invoke static invoke tests/type_propagation/block_test.toit // [[block]] -> {Null_|True_|float}
  29[041] - pop 1
  30[002] - pop, load local S0
- 32[053] - invoke static id tests/type_propagation/block_test.toit // {Null_|True_|float}
+ 32[053] - invoke static id tests/type_propagation/block_test.toit // [{Null_|True_|float}] -> {Null_|True_|float}
  35[089] - return null S3 0
 
 [block] in test_nesting tests/type_propagation/block_test.toit
@@ -136,18 +136,18 @@ test_nesting tests/type_propagation/block_test.toit
  20[041] - pop 1
  21[016] - load local 2
  22[005] - load outer S1 // {String_|SmallInteger_}
- 24[053] - invoke static id tests/type_propagation/block_test.toit // {String_|SmallInteger_}
+ 24[053] - invoke static id tests/type_propagation/block_test.toit // [{String_|SmallInteger_}] -> {String_|SmallInteger_}
  27[088] - return S1 1
 
 [block] in test_nesting tests/type_propagation/block_test.toit
  - argument 0: [block]
   0[029] - load [block] in [block] in test_nesting tests/type_propagation/block_test.toit
   5[038] - load block 0
-  7[053] - invoke static invoke tests/type_propagation/block_test.toit // {True_|float}
+  7[053] - invoke static invoke tests/type_propagation/block_test.toit // [[block]] -> {True_|float}
  10[041] - pop 1
  11[002] - pop, load local S2
  13[005] - load outer S1 // {Null_|True_|float}
- 15[053] - invoke static id tests/type_propagation/block_test.toit // {Null_|True_|float}
+ 15[053] - invoke static id tests/type_propagation/block_test.toit // [{Null_|True_|float}] -> {Null_|True_|float}
  18[088] - return S1 1
 
 [block] in [block] in test_nesting tests/type_propagation/block_test.toit
@@ -168,7 +168,7 @@ test_nesting tests/type_propagation/block_test.toit
  25[016] - load local 2
  26[005] - load outer S3 // [block]
  28[005] - load outer S1 // {True_|float}
- 30[053] - invoke static id tests/type_propagation/block_test.toit // {True_|float}
+ 30[053] - invoke static id tests/type_propagation/block_test.toit // [{True_|float}] -> {True_|float}
  33[088] - return S1 1
 
 test_catch tests/type_propagation/block_test.toit
@@ -176,7 +176,7 @@ test_catch tests/type_propagation/block_test.toit
   1[029] - load [block] in test_catch tests/type_propagation/block_test.toit
   6[094] - link try 0
   8[038] - load block 4
- 10[055] - invoke block S1 // {False_}
+ 10[055] - invoke block S1 // [[block]] -> {False_}
  12[041] - pop 1
  13[095] - unlink try 0
  15[096] - unwind
@@ -186,20 +186,20 @@ test_catch tests/type_propagation/block_test.toit
  23[038] - load block 0
  25[022] - load null
  26[022] - load null
- 27[053] - invoke static catch <sdk>/core/exceptions.toit // {*}
+ 27[053] - invoke static catch <sdk>/core/exceptions.toit // [[block], {Null_}, {Null_}] -> {*}
  30[041] - pop 1
  31[002] - pop, load local S0
- 33[053] - invoke static id tests/type_propagation/block_test.toit // {Null_|SmallInteger_}
+ 33[053] - invoke static id tests/type_propagation/block_test.toit // [{Null_|SmallInteger_}] -> {Null_|SmallInteger_}
  36[041] - pop 1
  37[022] - load null
  38[029] - load [block] in test_catch tests/type_propagation/block_test.toit
  43[038] - load block 0
  45[022] - load null
  46[022] - load null
- 47[053] - invoke static catch <sdk>/core/exceptions.toit // {*}
+ 47[053] - invoke static catch <sdk>/core/exceptions.toit // [[block], {Null_}, {Null_}] -> {*}
  50[041] - pop 1
  51[002] - pop, load local S0
- 53[053] - invoke static id tests/type_propagation/block_test.toit // {String_|Null_|float}
+ 53[053] - invoke static id tests/type_propagation/block_test.toit // [{String_|Null_|float}] -> {String_|Null_|float}
  56[089] - return null S4 0
 
 [block] in test_catch tests/type_propagation/block_test.toit
@@ -216,7 +216,7 @@ test_catch tests/type_propagation/block_test.toit
   3[006] - store outer S1
   5[041] - pop 1
   6[020] - load literal woops
-  8[053] - invoke static throw <sdk>/core/exceptions.toit // {}
+  8[053] - invoke static throw <sdk>/core/exceptions.toit // [{String_}] -> {}
  11[088] - return S1 1
 
 [block] in test_catch tests/type_propagation/block_test.toit
@@ -236,14 +236,14 @@ test_too_few_arguments tests/type_propagation/block_test.toit
   5[038] - load block 0
   7[022] - load null
   8[022] - load null
-  9[053] - invoke static catch <sdk>/core/exceptions.toit // {*}
+  9[053] - invoke static catch <sdk>/core/exceptions.toit // [[block], {Null_}, {Null_}] -> {*}
  12[089] - return null S2 0
 
 [block] in test_too_few_arguments tests/type_propagation/block_test.toit
  - argument 0: [block]
   0[029] - load [block] in [block] in test_too_few_arguments tests/type_propagation/block_test.toit
   5[038] - load block 0
-  7[053] - invoke static invoke tests/type_propagation/block_test.toit // {}
+  7[053] - invoke static invoke tests/type_propagation/block_test.toit // [[block]] -> {}
  10[004] - store local, pop S1
  12[088] - return S1 1
 
@@ -253,12 +253,12 @@ test_modify_outer tests/type_propagation/block_test.toit
   3[029] - load [block] in test_modify_outer tests/type_propagation/block_test.toit
   8[026] - load smi 2
  10[038] - load block 1
- 12[058] - invoke virtual repeat // {Null_}
+ 12[058] - invoke virtual repeat // [{SmallInteger_}, [block]] -> {Null_}
  16[041] - pop 1
  17[002] - pop, load local S1
- 19[053] - invoke static id tests/type_propagation/block_test.toit // {String_|SmallInteger_}
+ 19[053] - invoke static id tests/type_propagation/block_test.toit // [{String_|SmallInteger_}] -> {String_|SmallInteger_}
  22[002] - pop, load local S0
- 24[053] - invoke static id tests/type_propagation/block_test.toit // {String_|SmallInteger_}
+ 24[053] - invoke static id tests/type_propagation/block_test.toit // [{String_|SmallInteger_}] -> {String_|SmallInteger_}
  27[089] - return null S3 0
 
 [block] in test_modify_outer tests/type_propagation/block_test.toit
@@ -278,12 +278,12 @@ test_modify_outer_nested tests/type_propagation/block_test.toit
   3[029] - load [block] in test_modify_outer_nested tests/type_propagation/block_test.toit
   8[026] - load smi 2
  10[038] - load block 1
- 12[058] - invoke virtual repeat // {Null_}
+ 12[058] - invoke virtual repeat // [{SmallInteger_}, [block]] -> {Null_}
  16[041] - pop 1
  17[002] - pop, load local S1
- 19[053] - invoke static id tests/type_propagation/block_test.toit // {String_|SmallInteger_}
+ 19[053] - invoke static id tests/type_propagation/block_test.toit // [{String_|SmallInteger_}] -> {String_|SmallInteger_}
  22[002] - pop, load local S0
- 24[053] - invoke static id tests/type_propagation/block_test.toit // {String_|SmallInteger_}
+ 24[053] - invoke static id tests/type_propagation/block_test.toit // [{String_|SmallInteger_}] -> {String_|SmallInteger_}
  27[089] - return null S3 0
 
 [block] in test_modify_outer_nested tests/type_propagation/block_test.toit
@@ -291,14 +291,14 @@ test_modify_outer_nested tests/type_propagation/block_test.toit
   0[029] - load [block] in [block] in test_modify_outer_nested tests/type_propagation/block_test.toit
   5[026] - load smi 3
   7[038] - load block 1
-  9[058] - invoke virtual repeat // {Null_}
+  9[058] - invoke virtual repeat // [{SmallInteger_}, [block]] -> {Null_}
  13[041] - pop 1
  14[002] - pop, load local S2
  16[005] - load outer S2 // {String_|SmallInteger_}
- 18[053] - invoke static id tests/type_propagation/block_test.toit // {String_|SmallInteger_}
+ 18[053] - invoke static id tests/type_propagation/block_test.toit // [{String_|SmallInteger_}] -> {String_|SmallInteger_}
  21[002] - pop, load local S2
  23[005] - load outer S1 // {String_|SmallInteger_}
- 25[053] - invoke static id tests/type_propagation/block_test.toit // {String_|SmallInteger_}
+ 25[053] - invoke static id tests/type_propagation/block_test.toit // [{String_|SmallInteger_}] -> {String_|SmallInteger_}
  28[088] - return S1 1
 
 [block] in [block] in test_modify_outer_nested tests/type_propagation/block_test.toit
@@ -318,35 +318,35 @@ test_modify_outer_nested tests/type_propagation/block_test.toit
 test_recursion tests/type_propagation/block_test.toit
   0[029] - load [block] in test_recursion tests/type_propagation/block_test.toit
   5[038] - load block 0
-  7[053] - invoke static recursive_null tests/type_propagation/block_test.toit // {Null_|SmallInteger_}
+  7[053] - invoke static recursive_null tests/type_propagation/block_test.toit // [[block]] -> {Null_|SmallInteger_}
  10[040] - pop 2
  12[029] - load [block] in test_recursion tests/type_propagation/block_test.toit
  17[038] - load block 0
- 19[053] - invoke static recursive_null tests/type_propagation/block_test.toit // {Null_|False_}
+ 19[053] - invoke static recursive_null tests/type_propagation/block_test.toit // [[block]] -> {Null_|False_}
  22[040] - pop 2
  24[029] - load [block] in test_recursion tests/type_propagation/block_test.toit
  29[038] - load block 0
- 31[053] - invoke static recursive_call tests/type_propagation/block_test.toit // {SmallInteger_}
+ 31[053] - invoke static recursive_call tests/type_propagation/block_test.toit // [[block]] -> {SmallInteger_}
  34[040] - pop 2
  36[029] - load [block] in test_recursion tests/type_propagation/block_test.toit
  41[038] - load block 0
- 43[053] - invoke static recursive_call tests/type_propagation/block_test.toit // {True_}
+ 43[053] - invoke static recursive_call tests/type_propagation/block_test.toit // [[block]] -> {True_}
  46[040] - pop 2
  48[029] - load [block] in test_recursion tests/type_propagation/block_test.toit
  53[038] - load block 0
- 55[053] - invoke static recursive_a_null tests/type_propagation/block_test.toit // {Null_|SmallInteger_}
+ 55[053] - invoke static recursive_a_null tests/type_propagation/block_test.toit // [[block]] -> {Null_|SmallInteger_}
  58[040] - pop 2
  60[029] - load [block] in test_recursion tests/type_propagation/block_test.toit
  65[038] - load block 0
- 67[053] - invoke static recursive_a_null tests/type_propagation/block_test.toit // {String_|Null_}
+ 67[053] - invoke static recursive_a_null tests/type_propagation/block_test.toit // [[block]] -> {String_|Null_}
  70[040] - pop 2
  72[029] - load [block] in test_recursion tests/type_propagation/block_test.toit
  77[038] - load block 0
- 79[053] - invoke static recursive_a_call tests/type_propagation/block_test.toit // {SmallInteger_}
+ 79[053] - invoke static recursive_a_call tests/type_propagation/block_test.toit // [[block]] -> {SmallInteger_}
  82[040] - pop 2
  84[029] - load [block] in test_recursion tests/type_propagation/block_test.toit
  89[038] - load block 0
- 91[053] - invoke static recursive_a_call tests/type_propagation/block_test.toit // {String_}
+ 91[053] - invoke static recursive_a_call tests/type_propagation/block_test.toit // [[block]] -> {String_}
  94[089] - return null S2 0
 
 [block] in test_recursion tests/type_propagation/block_test.toit
@@ -392,15 +392,15 @@ test_recursion tests/type_propagation/block_test.toit
 test_dead tests/type_propagation/block_test.toit
   0[029] - load [block] in test_dead tests/type_propagation/block_test.toit
   5[038] - load block 0
-  7[053] - invoke static ignore tests/type_propagation/block_test.toit // {Null_}
+  7[053] - invoke static ignore tests/type_propagation/block_test.toit // [[block]] -> {Null_}
  10[040] - pop 2
  12[029] - load [block] in test_dead tests/type_propagation/block_test.toit
  17[038] - load block 0
- 19[053] - invoke static ignore tests/type_propagation/block_test.toit // {Null_}
+ 19[053] - invoke static ignore tests/type_propagation/block_test.toit // [[block]] -> {Null_}
  22[040] - pop 2
  24[029] - load [block] in test_dead tests/type_propagation/block_test.toit
  29[038] - load block 0
- 31[053] - invoke static ignore tests/type_propagation/block_test.toit // {Null_}
+ 31[053] - invoke static ignore tests/type_propagation/block_test.toit // [[block]] -> {Null_}
  34[089] - return null S2 0
 
 recursive_null tests/type_propagation/block_test.toit
@@ -409,11 +409,11 @@ recursive_null tests/type_propagation/block_test.toit
   3[082] - branch if false T21
   6[029] - load [block] in recursive_null tests/type_propagation/block_test.toit
  11[038] - load block 0
- 13[053] - invoke static recursive_null tests/type_propagation/block_test.toit // {Null_}
+ 13[053] - invoke static recursive_null tests/type_propagation/block_test.toit // [[block]] -> {Null_}
  16[004] - store local, pop S1
  18[088] - return S1 1
  21[016] - load local 2
- 22[055] - invoke block S1 // {Null_|False_|SmallInteger_}
+ 22[055] - invoke block S1 // [[block]] -> {Null_|False_|SmallInteger_}
  24[088] - return S1 1
 
 [block] in recursive_null tests/type_propagation/block_test.toit
@@ -426,10 +426,10 @@ recursive_call tests/type_propagation/block_test.toit
   0[053] - invoke static pick tests/type_propagation/block_test.toit // {True_|False_}
   3[082] - branch if false T13
   6[016] - load local 2
-  7[053] - invoke static recursive_call tests/type_propagation/block_test.toit // {True_|SmallInteger_}
+  7[053] - invoke static recursive_call tests/type_propagation/block_test.toit // [[block]] -> {True_|SmallInteger_}
  10[088] - return S1 1
  13[016] - load local 2
- 14[055] - invoke block S1 // {True_|SmallInteger_}
+ 14[055] - invoke block S1 // [[block]] -> {True_|SmallInteger_}
  16[088] - return S1 1
 
 recursive_a_null tests/type_propagation/block_test.toit
@@ -438,18 +438,18 @@ recursive_a_null tests/type_propagation/block_test.toit
   3[082] - branch if false T21
   6[029] - load [block] in recursive_a_null tests/type_propagation/block_test.toit
  11[038] - load block 0
- 13[053] - invoke static recursive_b_null tests/type_propagation/block_test.toit // {Null_}
+ 13[053] - invoke static recursive_b_null tests/type_propagation/block_test.toit // [[block]] -> {Null_}
  16[004] - store local, pop S1
  18[088] - return S1 1
  21[016] - load local 2
- 22[055] - invoke block S1 // {String_|Null_|SmallInteger_}
+ 22[055] - invoke block S1 // [[block]] -> {String_|Null_|SmallInteger_}
  24[088] - return S1 1
 
 recursive_b_null tests/type_propagation/block_test.toit
  - argument 0: [block]
   0[029] - load [block] in recursive_b_null tests/type_propagation/block_test.toit
   5[038] - load block 0
-  7[053] - invoke static recursive_a_null tests/type_propagation/block_test.toit // {Null_}
+  7[053] - invoke static recursive_a_null tests/type_propagation/block_test.toit // [[block]] -> {Null_}
  10[004] - store local, pop S1
  12[088] - return S1 1
 
@@ -463,23 +463,23 @@ recursive_a_call tests/type_propagation/block_test.toit
   0[053] - invoke static pick tests/type_propagation/block_test.toit // {True_|False_}
   3[082] - branch if false T13
   6[016] - load local 2
-  7[053] - invoke static recursive_b_call tests/type_propagation/block_test.toit // {String_|SmallInteger_}
+  7[053] - invoke static recursive_b_call tests/type_propagation/block_test.toit // [[block]] -> {String_|SmallInteger_}
  10[088] - return S1 1
  13[016] - load local 2
- 14[055] - invoke block S1 // {String_|SmallInteger_}
+ 14[055] - invoke block S1 // [[block]] -> {String_|SmallInteger_}
  16[088] - return S1 1
 
 recursive_b_call tests/type_propagation/block_test.toit
  - argument 0: [block]
   0[016] - load local 2
-  1[053] - invoke static recursive_a_call tests/type_propagation/block_test.toit // {String_|SmallInteger_}
+  1[053] - invoke static recursive_a_call tests/type_propagation/block_test.toit // [[block]] -> {String_|SmallInteger_}
   4[088] - return S1 1
 
 maybe_throw tests/type_propagation/block_test.toit
   0[053] - invoke static pick tests/type_propagation/block_test.toit // {True_|False_}
   3[082] - branch if false T12
   6[020] - load literal woops
-  8[053] - invoke static throw <sdk>/core/exceptions.toit // {}
+  8[053] - invoke static throw <sdk>/core/exceptions.toit // [{String_}] -> {}
  11[041] - pop 1
  12[089] - return null S0 0
 
@@ -494,15 +494,15 @@ ignore tests/type_propagation/block_test.toit
 
 pick tests/type_propagation/block_test.toit
   0[026] - load smi 100
-  2[053] - invoke static random <sdk>/core/utils.toit // {LargeInteger_|SmallInteger_}
+  2[053] - invoke static random <sdk>/core/utils.toit // [{SmallInteger_}] -> {LargeInteger_|SmallInteger_}
   5[026] - load smi 50
-  7[063] - invoke lt // {True_|False_}
+  7[063] - invoke lt // [{LargeInteger_|SmallInteger_}, {SmallInteger_}] -> {True_|False_}
   8[088] - return S1 0
 
 invoke tests/type_propagation/block_test.toit
  - argument 0: [block]
   0[016] - load local 2
-  1[055] - invoke block S1 // {String_|Null_|True_|float|SmallInteger_}
+  1[055] - invoke block S1 // [[block]] -> {String_|Null_|True_|float|SmallInteger_}
   3[088] - return S1 1
 
 invoke tests/type_propagation/block_test.toit
@@ -510,5 +510,5 @@ invoke tests/type_propagation/block_test.toit
  - argument 1: [block]
   0[016] - load local 2
   1[018] - load local 4
-  2[055] - invoke block S2 // {String_|True_|SmallInteger_}
+  2[055] - invoke block S2 // [[block], {String_|True_|SmallInteger_}] -> {String_|True_|SmallInteger_}
   4[088] - return S1 2
diff --git a/tests/type_propagation/gold/deltablue_test.gold b/tests/type_propagation/gold/deltablue_test.gold
index 8508e0506..7c509e5ba 100644
--- a/tests/type_propagation/gold/deltablue_test.gold
+++ b/tests/type_propagation/gold/deltablue_test.gold
@@ -2,16 +2,16 @@ main tests/type_propagation/deltablue_test.toit
   0[029] - load [block] in main tests/type_propagation/deltablue_test.toit
   5[026] - load smi 10
   7[038] - load block 1
-  9[058] - invoke virtual repeat // {Null_}
+  9[058] - invoke virtual repeat // [{SmallInteger_}, [block]] -> {Null_}
  13[089] - return null S2 0
 
 [block] in main tests/type_propagation/deltablue_test.toit
  - argument 0: [block]
   0[026] - load smi 50
-  2[053] - invoke static chain_test tests/type_propagation/deltablue_test.toit // {Null_}
+  2[053] - invoke static chain_test tests/type_propagation/deltablue_test.toit // [{SmallInteger_}] -> {Null_}
   5[041] - pop 1
   6[026] - load smi 50
-  8[053] - invoke static projection_test tests/type_propagation/deltablue_test.toit // {Null_}
+  8[053] - invoke static projection_test tests/type_propagation/deltablue_test.toit // [{SmallInteger_}] -> {Null_}
  11[088] - return S1 1
 
 Strength tests/type_propagation/deltablue_test.toit
@@ -31,49 +31,49 @@ Strength tests/type_propagation/deltablue_test.toit
 
 Strength.value tests/type_propagation/deltablue_test.toit
  - argument 0: {Strength}
-  0[009] - load field local 2 // {Null_|SmallInteger_}
+  0[009] - load field local 2 // [{Strength}] -> {Null_|SmallInteger_}
   2[088] - return S1 1
 
 Strength.next_weaker tests/type_propagation/deltablue_test.toit
  - argument 0: {Strength}
-  0[009] - load field local 2 // {Null_|SmallInteger_}
+  0[009] - load field local 2 // [{Strength}] -> {Null_|SmallInteger_}
   2[023] - load smi 0
-  3[062] - invoke eq // {True_|False_}
+  3[062] - invoke eq // [{Null_|SmallInteger_}, {SmallInteger_}] -> {True_|False_}
   4[082] - branch if false T14
   7[033] - load global var lazy G6 // {Strength}
   9[048] - as class Strength(47 - 48) // {True_}
  11[088] - return S1 1
- 14[009] - load field local 2 // {Null_|SmallInteger_}
+ 14[009] - load field local 2 // [{Strength}] -> {Null_|SmallInteger_}
  16[025] - load smi 1
- 17[062] - invoke eq // {True_|False_}
+ 17[062] - invoke eq // [{Null_|SmallInteger_}, {SmallInteger_}] -> {True_|False_}
  18[082] - branch if false T28
  21[033] - load global var lazy G5 // {Strength}
  23[048] - as class Strength(47 - 48) // {True_}
  25[088] - return S1 1
- 28[009] - load field local 2 // {Null_|SmallInteger_}
+ 28[009] - load field local 2 // [{Strength}] -> {Null_|SmallInteger_}
  30[026] - load smi 2
- 32[062] - invoke eq // {True_|False_}
+ 32[062] - invoke eq // [{Null_|SmallInteger_}, {SmallInteger_}] -> {True_|False_}
  33[082] - branch if false T43
  36[033] - load global var lazy G4 // {Strength}
  38[048] - as class Strength(47 - 48) // {True_}
  40[088] - return S1 1
- 43[009] - load field local 2 // {Null_|SmallInteger_}
+ 43[009] - load field local 2 // [{Strength}] -> {Null_|SmallInteger_}
  45[026] - load smi 3
- 47[062] - invoke eq // {True_|False_}
+ 47[062] - invoke eq // [{Null_|SmallInteger_}, {SmallInteger_}] -> {True_|False_}
  48[082] - branch if false T58
  51[033] - load global var lazy G3 // {Strength}
  53[048] - as class Strength(47 - 48) // {True_}
  55[088] - return S1 1
- 58[009] - load field local 2 // {Null_|SmallInteger_}
+ 58[009] - load field local 2 // [{Strength}] -> {Null_|SmallInteger_}
  60[026] - load smi 4
- 62[062] - invoke eq // {True_|False_}
+ 62[062] - invoke eq // [{Null_|SmallInteger_}, {SmallInteger_}] -> {True_|False_}
  63[082] - branch if false T73
  66[033] - load global var lazy G2 // {Strength}
  68[048] - as class Strength(47 - 48) // {True_}
  70[088] - return S1 1
- 73[009] - load field local 2 // {Null_|SmallInteger_}
+ 73[009] - load field local 2 // [{Strength}] -> {Null_|SmallInteger_}
  75[026] - load smi 5
- 77[062] - invoke eq // {True_|False_}
+ 77[062] - invoke eq // [{Null_|SmallInteger_}, {SmallInteger_}] -> {True_|False_}
  78[082] - branch if false T88
  81[033] - load global var lazy G1 // {Strength}
  83[048] - as class Strength(47 - 48) // {True_}
@@ -85,49 +85,49 @@ REQUIRED tests/type_propagation/deltablue_test.toit
   0[042] - allocate instance Strength
   2[023] - load smi 0
   3[020] - load literal required
-  5[053] - invoke static Strength tests/type_propagation/deltablue_test.toit // {Strength}
+  5[053] - invoke static Strength tests/type_propagation/deltablue_test.toit // [{Strength}, {SmallInteger_}, {String_}] -> {Strength}
   8[088] - return S1 0
 
 STRONG_REFERRED tests/type_propagation/deltablue_test.toit
   0[042] - allocate instance Strength
   2[025] - load smi 1
   3[020] - load literal strongPreferred
-  5[053] - invoke static Strength tests/type_propagation/deltablue_test.toit // {Strength}
+  5[053] - invoke static Strength tests/type_propagation/deltablue_test.toit // [{Strength}, {SmallInteger_}, {String_}] -> {Strength}
   8[088] - return S1 0
 
 PREFERRED tests/type_propagation/deltablue_test.toit
   0[042] - allocate instance Strength
   2[026] - load smi 2
   4[020] - load literal preferred
-  6[053] - invoke static Strength tests/type_propagation/deltablue_test.toit // {Strength}
+  6[053] - invoke static Strength tests/type_propagation/deltablue_test.toit // [{Strength}, {SmallInteger_}, {String_}] -> {Strength}
   9[088] - return S1 0
 
 STRONG_DEFAULT tests/type_propagation/deltablue_test.toit
   0[042] - allocate instance Strength
   2[026] - load smi 3
   4[020] - load literal strongDefault
-  6[053] - invoke static Strength tests/type_propagation/deltablue_test.toit // {Strength}
+  6[053] - invoke static Strength tests/type_propagation/deltablue_test.toit // [{Strength}, {SmallInteger_}, {String_}] -> {Strength}
   9[088] - return S1 0
 
 NORMAL tests/type_propagation/deltablue_test.toit
   0[042] - allocate instance Strength
   2[026] - load smi 4
   4[020] - load literal normal
-  6[053] - invoke static Strength tests/type_propagation/deltablue_test.toit // {Strength}
+  6[053] - invoke static Strength tests/type_propagation/deltablue_test.toit // [{Strength}, {SmallInteger_}, {String_}] -> {Strength}
   9[088] - return S1 0
 
 WEAK_DEFAULT tests/type_propagation/deltablue_test.toit
   0[042] - allocate instance Strength
   2[026] - load smi 5
   4[020] - load literal weakDefault
-  6[053] - invoke static Strength tests/type_propagation/deltablue_test.toit // {Strength}
+  6[053] - invoke static Strength tests/type_propagation/deltablue_test.toit // [{Strength}, {SmallInteger_}, {String_}] -> {Strength}
   9[088] - return S1 0
 
 WEAKEST tests/type_propagation/deltablue_test.toit
   0[042] - allocate instance Strength
   2[026] - load smi 6
   4[020] - load literal weakest
-  6[053] - invoke static Strength tests/type_propagation/deltablue_test.toit // {Strength}
+  6[053] - invoke static Strength tests/type_propagation/deltablue_test.toit // [{Strength}, {SmallInteger_}, {String_}] -> {Strength}
   9[088] - return S1 0
 
 stronger tests/type_propagation/deltablue_test.toit
@@ -135,9 +135,9 @@ stronger tests/type_propagation/deltablue_test.toit
  - argument 1: {Null_|Strength}
   0[052] - load local, as class, pop 3 - Strength(47 - 48) // {True_|False_}
   2[052] - load local, as class, pop 2 - Strength(47 - 48) // {True_|False_}
-  4[009] - load field local 3 // {Null_|SmallInteger_}
-  6[009] - load field local 3 // {Null_|SmallInteger_}
-  8[063] - invoke lt // {True_|False_}
+  4[009] - load field local 3 // [{Strength}] -> {Null_|SmallInteger_}
+  6[009] - load field local 3 // [{Strength}] -> {Null_|SmallInteger_}
+  8[063] - invoke lt // [{Null_|SmallInteger_}, {Null_|SmallInteger_}] -> {True_|False_}
   9[048] - as class True_(18 - 20) // {True_}
  11[088] - return S1 2
 
@@ -146,9 +146,9 @@ weaker tests/type_propagation/deltablue_test.toit
  - argument 1: {Null_|Strength}
   0[052] - load local, as class, pop 3 - Strength(47 - 48) // {True_|False_}
   2[052] - load local, as class, pop 2 - Strength(47 - 48) // {True_|False_}
-  4[009] - load field local 3 // {Null_|SmallInteger_}
-  6[009] - load field local 3 // {Null_|SmallInteger_}
-  8[064] - invoke gt // {True_|False_}
+  4[009] - load field local 3 // [{Strength}] -> {Null_|SmallInteger_}
+  6[009] - load field local 3 // [{Strength}] -> {Null_|SmallInteger_}
+  8[064] - invoke gt // [{Null_|SmallInteger_}, {Null_|SmallInteger_}] -> {True_|False_}
   9[048] - as class True_(18 - 20) // {True_}
  11[088] - return S1 2
 
@@ -159,7 +159,7 @@ weakest tests/type_propagation/deltablue_test.toit
   2[052] - load local, as class, pop 2 - Strength(47 - 48) // {True_|False_}
   4[017] - load local 3
   5[017] - load local 3
-  6[053] - invoke static weaker tests/type_propagation/deltablue_test.toit // {True_|False_}
+  6[053] - invoke static weaker tests/type_propagation/deltablue_test.toit // [{Strength}, {Strength}] -> {True_|False_}
   9[082] - branch if false T16
  12[017] - load local 3
  13[080] - branch T17
@@ -169,7 +169,7 @@ weakest tests/type_propagation/deltablue_test.toit
 
 Constraint.strength tests/type_propagation/deltablue_test.toit
  - argument 0: {EqualityConstraint|ScaleConstraint|EditConstraint|StayConstraint}
-  0[009] - load field local 2 // {Null_|Strength}
+  0[009] - load field local 2 // [{EqualityConstraint|ScaleConstraint|EditConstraint|StayConstraint}] -> {Null_|Strength}
   2[088] - return S1 1
 
 Constraint tests/type_propagation/deltablue_test.toit
@@ -185,11 +185,11 @@ Constraint tests/type_propagation/deltablue_test.toit
 Constraint.add_constraint tests/type_propagation/deltablue_test.toit
  - argument 0: {EqualityConstraint|ScaleConstraint|EditConstraint|StayConstraint}
   0[016] - load local 2
-  1[058] - invoke virtual add_to_graph // {Null_}
+  1[058] - invoke virtual add_to_graph // [{EqualityConstraint|ScaleConstraint|EditConstraint|StayConstraint}] -> {Null_}
   5[041] - pop 1
   6[030] - load global var G7 // {Null_|Planner}
   8[017] - load local 3
-  9[058] - invoke virtual incremental_add // {Null_}
+  9[058] - invoke virtual incremental_add // [{Null_|Planner}, {EqualityConstraint|ScaleConstraint|EditConstraint|StayConstraint}] -> {Null_}
  13[089] - return null S1 1
 
 Constraint.satisfy tests/type_propagation/deltablue_test.toit
@@ -198,30 +198,30 @@ Constraint.satisfy tests/type_propagation/deltablue_test.toit
   0[052] - load local, as class, pop 2 - LargeInteger_(22 - 24) // {True_}
   2[017] - load local 3
   3[017] - load local 3
-  4[058] - invoke virtual choose_method // {Null_}
+  4[058] - invoke virtual choose_method // [{EqualityConstraint|ScaleConstraint|EditConstraint|StayConstraint}, {LargeInteger_|SmallInteger_}] -> {Null_}
   8[002] - pop, load local S3
- 10[060] - invoke virtual get is_satisfied // {Null_|True_|False_}
+ 10[060] - invoke virtual get is_satisfied // [{EqualityConstraint|ScaleConstraint|EditConstraint|StayConstraint}] -> {Null_|True_|False_}
  13[081] - branch if true T36
- 16[009] - load field local 3 // {Null_|Strength}
+ 16[009] - load field local 3 // [{EqualityConstraint|ScaleConstraint|EditConstraint|StayConstraint}] -> {Null_|Strength}
  18[033] - load global var lazy G0 // {Strength}
- 20[062] - invoke eq // {True_|False_}
+ 20[062] - invoke eq // [{Null_|Strength}, {Strength}] -> {True_|False_}
  21[082] - branch if false T30
  24[020] - load literal Could not satisfy a required constraint!
- 26[053] - invoke static throw <sdk>/core/exceptions.toit // {}
+ 26[053] - invoke static throw <sdk>/core/exceptions.toit // [{String_}] -> {}
  29[041] - pop 1
  30[022] - load null
  31[048] - as class EqualityConstraint?(43 - 47) // {True_}
  33[088] - return S1 2
  36[017] - load local 3
  37[017] - load local 3
- 38[058] - invoke virtual mark_inputs // {Null_}
+ 38[058] - invoke virtual mark_inputs // [{EqualityConstraint|ScaleConstraint|EditConstraint|StayConstraint}, {LargeInteger_|SmallInteger_}] -> {Null_}
  42[002] - pop, load local S3
- 44[058] - invoke virtual output // {Null_|Variable}
- 48[009] - load field local 32 // {Null_|EqualityConstraint|ScaleConstraint|EditConstraint|StayConstraint}
+ 44[058] - invoke virtual output // [{EqualityConstraint|ScaleConstraint|EditConstraint|StayConstraint}] -> {Null_|Variable}
+ 48[009] - load field local 32 // [{Null_|Variable}] -> {Null_|EqualityConstraint|ScaleConstraint|EditConstraint|StayConstraint}
  50[014] - load local 0
  51[082] - branch if false T60
  54[014] - load local 0
- 55[058] - invoke virtual mark_unsatisfied // {Null_}
+ 55[058] - invoke virtual mark_unsatisfied // [{Null_|EqualityConstraint|ScaleConstraint|EditConstraint|StayConstraint}] -> {Null_}
  59[041] - pop 1
  60[015] - load local 1
  61[000] - load local S6
@@ -229,10 +229,10 @@ Constraint.satisfy tests/type_propagation/deltablue_test.toit
  65[030] - load global var G7 // {Null_|Planner}
  67[000] - load local S6
  69[000] - load local S6
- 71[058] - invoke virtual add_propagate // {True_|False_}
+ 71[058] - invoke virtual add_propagate // [{Null_|Planner}, {EqualityConstraint|ScaleConstraint|EditConstraint|StayConstraint}, {LargeInteger_|SmallInteger_}] -> {True_|False_}
  75[081] - branch if true T84
  78[020] - load literal Cycle encountered
- 80[053] - invoke static throw <sdk>/core/exceptions.toit // {}
+ 80[053] - invoke static throw <sdk>/core/exceptions.toit // [{String_}] -> {}
  83[041] - pop 1
  84[015] - load local 1
  85[019] - load local 5
@@ -244,14 +244,14 @@ Constraint.satisfy tests/type_propagation/deltablue_test.toit
 Constraint.destroy_constraint tests/type_propagation/deltablue_test.toit
  - argument 0: {EditConstraint}
   0[016] - load local 2
-  1[060] - invoke virtual get is_satisfied // {Null_|True_|False_}
+  1[060] - invoke virtual get is_satisfied // [{EditConstraint}] -> {Null_|True_|False_}
   4[082] - branch if false T15
   7[030] - load global var G7 // {Null_|Planner}
   9[017] - load local 3
- 10[058] - invoke virtual incremental_remove // {Null_}
+ 10[058] - invoke virtual incremental_remove // [{Null_|Planner}, {EditConstraint}] -> {Null_}
  14[041] - pop 1
  15[016] - load local 2
- 16[058] - invoke virtual remove_from_graph // {Null_}
+ 16[058] - invoke virtual remove_from_graph // [{EditConstraint}] -> {Null_}
  20[089] - return null S1 1
 
 Constraint.is_input tests/type_propagation/deltablue_test.toit
@@ -262,7 +262,7 @@ Constraint.is_input tests/type_propagation/deltablue_test.toit
 
 UnaryConstraint.is_satisfied tests/type_propagation/deltablue_test.toit
  - argument 0: {EditConstraint|StayConstraint}
-  0[009] - load field local 34 // {Null_|True_|False_}
+  0[009] - load field local 34 // [{EditConstraint|StayConstraint}] -> {Null_|True_|False_}
   2[088] - return S1 1
 
 UnaryConstraint tests/type_propagation/deltablue_test.toit
@@ -280,17 +280,17 @@ UnaryConstraint tests/type_propagation/deltablue_test.toit
  13[013] - store field, pop 2
  15[018] - load local 4
  16[018] - load local 4
- 17[053] - invoke static Constraint tests/type_propagation/deltablue_test.toit // {EditConstraint|StayConstraint}
+ 17[053] - invoke static Constraint tests/type_propagation/deltablue_test.toit // [{EditConstraint|StayConstraint}, {Strength}] -> {EditConstraint|StayConstraint}
  20[002] - pop, load local S4
- 22[053] - invoke static Constraint.add_constraint tests/type_propagation/deltablue_test.toit // {Null_}
+ 22[053] - invoke static Constraint.add_constraint tests/type_propagation/deltablue_test.toit // [{EditConstraint|StayConstraint}] -> {Null_}
  25[002] - pop, load local S4
  27[088] - return S1 3
 
 UnaryConstraint.add_to_graph tests/type_propagation/deltablue_test.toit
  - argument 0: {EditConstraint|StayConstraint}
-  0[009] - load field local 18 // {Null_|Variable}
+  0[009] - load field local 18 // [{EditConstraint|StayConstraint}] -> {Null_|Variable}
   2[017] - load local 3
-  3[053] - invoke static Variable.add_constraint tests/type_propagation/deltablue_test.toit // {Null_}
+  3[053] - invoke static Variable.add_constraint tests/type_propagation/deltablue_test.toit // [{Null_|Variable}, {EditConstraint|StayConstraint}] -> {Null_}
   6[002] - pop, load local S2
   8[020] - load literal false
  10[048] - as class True_(18 - 20) // {True_}
@@ -302,20 +302,20 @@ UnaryConstraint.choose_method tests/type_propagation/deltablue_test.toit
  - argument 1: {LargeInteger_|SmallInteger_}
   0[052] - load local, as class, pop 2 - LargeInteger_(22 - 24) // {True_}
   2[017] - load local 3
-  3[009] - load field local 20 // {Null_|Variable}
-  5[007] - load field 3 // {Null_|LargeInteger_|SmallInteger_}
+  3[009] - load field local 20 // [{EditConstraint|StayConstraint}] -> {Null_|Variable}
+  5[007] - load field 3 // [{Null_|Variable}] -> {Null_|LargeInteger_|SmallInteger_}
   7[018] - load local 4
-  8[062] - invoke eq // {True_|False_}
+  8[062] - invoke eq // [{Null_|LargeInteger_|SmallInteger_}, {LargeInteger_|SmallInteger_}] -> {True_|False_}
   9[081] - branch if true T17
  12[020] - load literal true
  14[080] - branch T19
  17[020] - load literal false
  19[014] - load local 0
  20[082] - branch if false T32
- 23[010] - pop, load field local 4 // {Null_|Strength}
- 25[009] - load field local 21 // {Null_|Variable}
- 27[007] - load field 4 // {Null_|Strength}
- 29[053] - invoke static stronger tests/type_propagation/deltablue_test.toit // {True_|False_}
+ 23[010] - pop, load field local 4 // [{EditConstraint|StayConstraint}] -> {Null_|Strength}
+ 25[009] - load field local 21 // [{EditConstraint|StayConstraint}] -> {Null_|Variable}
+ 27[007] - load field 4 // [{Null_|Variable}] -> {Null_|Strength}
+ 29[053] - invoke static stronger tests/type_propagation/deltablue_test.toit // [{Null_|Strength}, {Null_|Strength}] -> {True_|False_}
  32[048] - as class True_(18 - 20) // {True_}
  34[013] - store field, pop 2
  36[089] - return null S0 2
@@ -328,27 +328,27 @@ UnaryConstraint.mark_inputs tests/type_propagation/deltablue_test.toit
 
 UnaryConstraint.output tests/type_propagation/deltablue_test.toit
  - argument 0: {EditConstraint|StayConstraint}
-  0[009] - load field local 18 // {Null_|Variable}
+  0[009] - load field local 18 // [{EditConstraint|StayConstraint}] -> {Null_|Variable}
   2[088] - return S1 1
 
 UnaryConstraint.recalculate tests/type_propagation/deltablue_test.toit
  - argument 0: {EditConstraint|StayConstraint}
-  0[009] - load field local 18 // {Null_|Variable}
-  2[009] - load field local 3 // {Null_|Strength}
+  0[009] - load field local 18 // [{EditConstraint|StayConstraint}] -> {Null_|Variable}
+  2[009] - load field local 3 // [{EditConstraint|StayConstraint}] -> {Null_|Strength}
   4[013] - store field, pop 4
-  6[009] - load field local 18 // {Null_|Variable}
+  6[009] - load field local 18 // [{EditConstraint|StayConstraint}] -> {Null_|Variable}
   8[017] - load local 3
-  9[058] - invoke virtual is_input // {True_|False_}
+  9[058] - invoke virtual is_input // [{EditConstraint|StayConstraint}] -> {True_|False_}
  13[081] - branch if true T21
  16[020] - load literal true
  18[080] - branch T23
  21[020] - load literal false
  23[013] - store field, pop 5
- 25[009] - load field local 18 // {Null_|Variable}
- 27[007] - load field 5 // {Null_|True_|False_}
+ 25[009] - load field local 18 // [{EditConstraint|StayConstraint}] -> {Null_|Variable}
+ 27[007] - load field 5 // [{Null_|Variable}] -> {Null_|True_|False_}
  29[082] - branch if false T38
  32[016] - load local 2
- 33[058] - invoke virtual execute // {Null_}
+ 33[058] - invoke virtual execute // [{EditConstraint|StayConstraint}] -> {Null_}
  37[041] - pop 1
  38[089] - return null S0 1
 
@@ -370,9 +370,9 @@ UnaryConstraint.inputs_known tests/type_propagation/deltablue_test.toit
 
 UnaryConstraint.remove_from_graph tests/type_propagation/deltablue_test.toit
  - argument 0: {EditConstraint|StayConstraint}
-  0[009] - load field local 18 // {Null_|Variable}
+  0[009] - load field local 18 // [{EditConstraint|StayConstraint}] -> {Null_|Variable}
   2[017] - load local 3
-  3[053] - invoke static Variable.remove_constraint tests/type_propagation/deltablue_test.toit // {Null_}
+  3[053] - invoke static Variable.remove_constraint tests/type_propagation/deltablue_test.toit // [{Null_|Variable}, {EditConstraint|StayConstraint}] -> {Null_}
   6[002] - pop, load local S2
   8[020] - load literal false
  10[048] - as class True_(18 - 20) // {True_}
@@ -388,7 +388,7 @@ StayConstraint tests/type_propagation/deltablue_test.toit
   4[018] - load local 4
   5[018] - load local 4
   6[018] - load local 4
-  7[053] - invoke static UnaryConstraint tests/type_propagation/deltablue_test.toit // {StayConstraint}
+  7[053] - invoke static UnaryConstraint tests/type_propagation/deltablue_test.toit // [{StayConstraint}, {Strength}, {Variable}] -> {StayConstraint}
  10[002] - pop, load local S4
  12[088] - return S1 3
 
@@ -405,7 +405,7 @@ EditConstraint tests/type_propagation/deltablue_test.toit
   4[018] - load local 4
   5[018] - load local 4
   6[018] - load local 4
-  7[053] - invoke static UnaryConstraint tests/type_propagation/deltablue_test.toit // {EditConstraint}
+  7[053] - invoke static UnaryConstraint tests/type_propagation/deltablue_test.toit // [{EditConstraint}, {Strength}, {Variable}] -> {EditConstraint}
  10[002] - pop, load local S4
  12[088] - return S1 3
 
@@ -439,9 +439,9 @@ BinaryConstraint tests/type_propagation/deltablue_test.toit
  18[013] - store field, pop 3
  20[019] - load local 5
  21[019] - load local 5
- 22[053] - invoke static Constraint tests/type_propagation/deltablue_test.toit // {EqualityConstraint|ScaleConstraint}
+ 22[053] - invoke static Constraint tests/type_propagation/deltablue_test.toit // [{EqualityConstraint|ScaleConstraint}, {Strength}] -> {EqualityConstraint|ScaleConstraint}
  25[002] - pop, load local S5
- 27[053] - invoke static Constraint.add_constraint tests/type_propagation/deltablue_test.toit // {Null_}
+ 27[053] - invoke static Constraint.add_constraint tests/type_propagation/deltablue_test.toit // [{EqualityConstraint|ScaleConstraint}] -> {Null_}
  30[002] - pop, load local S5
  32[088] - return S1 4
 
@@ -449,62 +449,62 @@ BinaryConstraint.choose_method tests/type_propagation/deltablue_test.toit
  - argument 0: {EqualityConstraint|ScaleConstraint}
  - argument 1: {LargeInteger_|SmallInteger_}
   0[052] - load local, as class, pop 2 - LargeInteger_(22 - 24) // {True_}
-  2[009] - load field local 19 // {Null_|Variable}
-  4[007] - load field 3 // {Null_|LargeInteger_|SmallInteger_}
+  2[009] - load field local 19 // [{EqualityConstraint|ScaleConstraint}] -> {Null_|Variable}
+  4[007] - load field 3 // [{Null_|Variable}] -> {Null_|LargeInteger_|SmallInteger_}
   6[017] - load local 3
-  7[062] - invoke eq // {True_|False_}
+  7[062] - invoke eq // [{Null_|LargeInteger_|SmallInteger_}, {LargeInteger_|SmallInteger_}] -> {True_|False_}
   8[082] - branch if false T44
  11[017] - load local 3
  12[025] - load smi 1
- 13[009] - load field local 37 // {Null_|Variable}
- 15[007] - load field 3 // {Null_|LargeInteger_|SmallInteger_}
+ 13[009] - load field local 37 // [{EqualityConstraint|ScaleConstraint}] -> {Null_|Variable}
+ 15[007] - load field 3 // [{Null_|Variable}] -> {Null_|LargeInteger_|SmallInteger_}
  17[019] - load local 5
- 18[062] - invoke eq // {True_|False_}
+ 18[062] - invoke eq // [{Null_|LargeInteger_|SmallInteger_}, {LargeInteger_|SmallInteger_}] -> {True_|False_}
  19[081] - branch if true T37
- 22[009] - load field local 5 // {Null_|Strength}
- 24[009] - load field local 38 // {Null_|Variable}
- 26[007] - load field 4 // {Null_|Strength}
- 28[053] - invoke static stronger tests/type_propagation/deltablue_test.toit // {True_|False_}
+ 22[009] - load field local 5 // [{EqualityConstraint|ScaleConstraint}] -> {Null_|Strength}
+ 24[009] - load field local 38 // [{EqualityConstraint|ScaleConstraint}] -> {Null_|Variable}
+ 26[007] - load field 4 // [{Null_|Variable}] -> {Null_|Strength}
+ 28[053] - invoke static stronger tests/type_propagation/deltablue_test.toit // [{Null_|Strength}, {Null_|Strength}] -> {True_|False_}
  31[082] - branch if false T37
  34[041] - pop 1
  35[026] - load smi 2
  37[048] - as class LargeInteger_(22 - 24) // {True_}
  39[013] - store field, pop 3
  41[080] - branch T143
- 44[009] - load field local 35 // {Null_|Variable}
- 46[007] - load field 3 // {Null_|LargeInteger_|SmallInteger_}
+ 44[009] - load field local 35 // [{EqualityConstraint|ScaleConstraint}] -> {Null_|Variable}
+ 46[007] - load field 3 // [{Null_|Variable}] -> {Null_|LargeInteger_|SmallInteger_}
  48[017] - load local 3
- 49[062] - invoke eq // {True_|False_}
+ 49[062] - invoke eq // [{Null_|LargeInteger_|SmallInteger_}, {LargeInteger_|SmallInteger_}] -> {True_|False_}
  50[082] - branch if false T85
  53[017] - load local 3
  54[025] - load smi 1
- 55[009] - load field local 21 // {Null_|Variable}
- 57[007] - load field 3 // {Null_|LargeInteger_|SmallInteger_}
+ 55[009] - load field local 21 // [{EqualityConstraint|ScaleConstraint}] -> {Null_|Variable}
+ 57[007] - load field 3 // [{Null_|Variable}] -> {Null_|LargeInteger_|SmallInteger_}
  59[019] - load local 5
- 60[062] - invoke eq // {True_|False_}
+ 60[062] - invoke eq // [{Null_|LargeInteger_|SmallInteger_}, {LargeInteger_|SmallInteger_}] -> {True_|False_}
  61[081] - branch if true T78
- 64[009] - load field local 5 // {Null_|Strength}
- 66[009] - load field local 22 // {Null_|Variable}
- 68[007] - load field 4 // {Null_|Strength}
- 70[053] - invoke static stronger tests/type_propagation/deltablue_test.toit // {True_|False_}
+ 64[009] - load field local 5 // [{EqualityConstraint|ScaleConstraint}] -> {Null_|Strength}
+ 66[009] - load field local 22 // [{EqualityConstraint|ScaleConstraint}] -> {Null_|Variable}
+ 68[007] - load field 4 // [{Null_|Variable}] -> {Null_|Strength}
+ 70[053] - invoke static stronger tests/type_propagation/deltablue_test.toit // [{Null_|Strength}, {Null_|Strength}] -> {True_|False_}
  73[082] - branch if false T78
  76[041] - pop 1
  77[023] - load smi 0
  78[048] - as class LargeInteger_(22 - 24) // {True_}
  80[013] - store field, pop 3
  82[080] - branch T143
- 85[009] - load field local 19 // {Null_|Variable}
- 87[007] - load field 4 // {Null_|Strength}
- 89[009] - load field local 36 // {Null_|Variable}
- 91[007] - load field 4 // {Null_|Strength}
- 93[053] - invoke static weaker tests/type_propagation/deltablue_test.toit // {True_|False_}
+ 85[009] - load field local 19 // [{EqualityConstraint|ScaleConstraint}] -> {Null_|Variable}
+ 87[007] - load field 4 // [{Null_|Variable}] -> {Null_|Strength}
+ 89[009] - load field local 36 // [{EqualityConstraint|ScaleConstraint}] -> {Null_|Variable}
+ 91[007] - load field 4 // [{Null_|Variable}] -> {Null_|Strength}
+ 93[053] - invoke static weaker tests/type_propagation/deltablue_test.toit // [{Null_|Strength}, {Null_|Strength}] -> {True_|False_}
  96[082] - branch if false T122
  99[017] - load local 3
 100[025] - load smi 1
-101[009] - load field local 5 // {Null_|Strength}
-103[009] - load field local 22 // {Null_|Variable}
-105[007] - load field 4 // {Null_|Strength}
-107[053] - invoke static stronger tests/type_propagation/deltablue_test.toit // {True_|False_}
+101[009] - load field local 5 // [{EqualityConstraint|ScaleConstraint}] -> {Null_|Strength}
+103[009] - load field local 22 // [{EqualityConstraint|ScaleConstraint}] -> {Null_|Variable}
+105[007] - load field 4 // [{Null_|Variable}] -> {Null_|Strength}
+107[053] - invoke static stronger tests/type_propagation/deltablue_test.toit // [{Null_|Strength}, {Null_|Strength}] -> {True_|False_}
 110[082] - branch if false T115
 113[041] - pop 1
 114[023] - load smi 0
@@ -513,10 +513,10 @@ BinaryConstraint.choose_method tests/type_propagation/deltablue_test.toit
 119[080] - branch T143
 122[017] - load local 3
 123[023] - load smi 0
-124[009] - load field local 5 // {Null_|Strength}
-126[009] - load field local 38 // {Null_|Variable}
-128[007] - load field 4 // {Null_|Strength}
-130[053] - invoke static stronger tests/type_propagation/deltablue_test.toit // {True_|False_}
+124[009] - load field local 5 // [{EqualityConstraint|ScaleConstraint}] -> {Null_|Strength}
+126[009] - load field local 38 // [{EqualityConstraint|ScaleConstraint}] -> {Null_|Variable}
+128[007] - load field 4 // [{Null_|Variable}] -> {Null_|Strength}
+130[053] - invoke static stronger tests/type_propagation/deltablue_test.toit // [{Null_|Strength}, {Null_|Strength}] -> {True_|False_}
 133[082] - branch if false T139
 136[041] - pop 1
 137[026] - load smi 2
@@ -526,12 +526,12 @@ BinaryConstraint.choose_method tests/type_propagation/deltablue_test.toit
 
 BinaryConstraint.add_to_graph tests/type_propagation/deltablue_test.toit
  - argument 0: {EqualityConstraint|ScaleConstraint}
-  0[009] - load field local 18 // {Null_|Variable}
+  0[009] - load field local 18 // [{EqualityConstraint|ScaleConstraint}] -> {Null_|Variable}
   2[017] - load local 3
-  3[053] - invoke static Variable.add_constraint tests/type_propagation/deltablue_test.toit // {Null_}
-  6[010] - pop, load field local 34 // {Null_|Variable}
+  3[053] - invoke static Variable.add_constraint tests/type_propagation/deltablue_test.toit // [{Null_|Variable}, {EqualityConstraint|ScaleConstraint}] -> {Null_}
+  6[010] - pop, load field local 34 // [{EqualityConstraint|ScaleConstraint}] -> {Null_|Variable}
   8[017] - load local 3
-  9[053] - invoke static Variable.add_constraint tests/type_propagation/deltablue_test.toit // {Null_}
+  9[053] - invoke static Variable.add_constraint tests/type_propagation/deltablue_test.toit // [{Null_|Variable}, {EqualityConstraint|ScaleConstraint}] -> {Null_}
  12[002] - pop, load local S2
  14[025] - load smi 1
  15[048] - as class LargeInteger_(22 - 24) // {True_}
@@ -540,9 +540,9 @@ BinaryConstraint.add_to_graph tests/type_propagation/deltablue_test.toit
 
 BinaryConstraint.is_satisfied tests/type_propagation/deltablue_test.toit
  - argument 0: {EqualityConstraint|ScaleConstraint}
-  0[009] - load field local 50 // {Null_|SmallInteger_}
+  0[009] - load field local 50 // [{EqualityConstraint|ScaleConstraint}] -> {Null_|SmallInteger_}
   2[025] - load smi 1
-  3[062] - invoke eq // {True_|False_}
+  3[062] - invoke eq // [{Null_|SmallInteger_}, {SmallInteger_}] -> {True_|False_}
   4[081] - branch if true T12
   7[020] - load literal true
   9[080] - branch T14
@@ -555,53 +555,53 @@ BinaryConstraint.mark_inputs tests/type_propagation/deltablue_test.toit
  - argument 1: {LargeInteger_|SmallInteger_}
   0[052] - load local, as class, pop 2 - LargeInteger_(22 - 24) // {True_}
   2[017] - load local 3
-  3[053] - invoke static BinaryConstraint.input tests/type_propagation/deltablue_test.toit // {Variable}
+  3[053] - invoke static BinaryConstraint.input tests/type_propagation/deltablue_test.toit // [{EqualityConstraint|ScaleConstraint}] -> {Variable}
   6[017] - load local 3
   7[013] - store field, pop 3
   9[089] - return null S0 2
 
 BinaryConstraint.input tests/type_propagation/deltablue_test.toit
  - argument 0: {EqualityConstraint|ScaleConstraint}
-  0[009] - load field local 50 // {Null_|SmallInteger_}
+  0[009] - load field local 50 // [{EqualityConstraint|ScaleConstraint}] -> {Null_|SmallInteger_}
   2[026] - load smi 2
-  4[062] - invoke eq // {True_|False_}
+  4[062] - invoke eq // [{Null_|SmallInteger_}, {SmallInteger_}] -> {True_|False_}
   5[082] - branch if false T13
-  8[009] - load field local 18 // {Null_|Variable}
+  8[009] - load field local 18 // [{EqualityConstraint|ScaleConstraint}] -> {Null_|Variable}
  10[080] - branch T15
- 13[009] - load field local 34 // {Null_|Variable}
+ 13[009] - load field local 34 // [{EqualityConstraint|ScaleConstraint}] -> {Null_|Variable}
  15[048] - as class Variable(42 - 43) // {True_|False_}
  17[088] - return S1 1
 
 BinaryConstraint.output tests/type_propagation/deltablue_test.toit
  - argument 0: {EqualityConstraint|ScaleConstraint}
-  0[009] - load field local 50 // {Null_|SmallInteger_}
+  0[009] - load field local 50 // [{EqualityConstraint|ScaleConstraint}] -> {Null_|SmallInteger_}
   2[026] - load smi 2
-  4[062] - invoke eq // {True_|False_}
+  4[062] - invoke eq // [{Null_|SmallInteger_}, {SmallInteger_}] -> {True_|False_}
   5[082] - branch if false T13
-  8[009] - load field local 34 // {Null_|Variable}
+  8[009] - load field local 34 // [{EqualityConstraint|ScaleConstraint}] -> {Null_|Variable}
  10[080] - branch T15
- 13[009] - load field local 18 // {Null_|Variable}
+ 13[009] - load field local 18 // [{EqualityConstraint|ScaleConstraint}] -> {Null_|Variable}
  15[048] - as class Variable(42 - 43) // {True_|False_}
  17[088] - return S1 1
 
 BinaryConstraint.recalculate tests/type_propagation/deltablue_test.toit
  - argument 0: {EqualityConstraint}
   0[016] - load local 2
-  1[053] - invoke static BinaryConstraint.input tests/type_propagation/deltablue_test.toit // {Variable}
+  1[053] - invoke static BinaryConstraint.input tests/type_propagation/deltablue_test.toit // [{EqualityConstraint}] -> {Variable}
   4[017] - load local 3
-  5[053] - invoke static BinaryConstraint.output tests/type_propagation/deltablue_test.toit // {Variable}
+  5[053] - invoke static BinaryConstraint.output tests/type_propagation/deltablue_test.toit // [{EqualityConstraint}] -> {Variable}
   8[014] - load local 0
-  9[009] - load field local 5 // {Null_|Strength}
- 11[009] - load field local 67 // {Null_|Strength}
- 13[053] - invoke static weakest tests/type_propagation/deltablue_test.toit // {Strength}
+  9[009] - load field local 5 // [{EqualityConstraint}] -> {Null_|Strength}
+ 11[009] - load field local 67 // [{Variable}] -> {Null_|Strength}
+ 13[053] - invoke static weakest tests/type_propagation/deltablue_test.toit // [{Null_|Strength}, {Null_|Strength}] -> {Strength}
  16[013] - store field, pop 4
  18[014] - load local 0
- 19[009] - load field local 82 // {Null_|True_|False_}
+ 19[009] - load field local 82 // [{Variable}] -> {Null_|True_|False_}
  21[013] - store field, pop 5
- 23[009] - load field local 80 // {Null_|True_|False_}
+ 23[009] - load field local 80 // [{Variable}] -> {Null_|True_|False_}
  25[082] - branch if false T34
  28[018] - load local 4
- 29[058] - invoke virtual execute // {Null_}
+ 29[058] - invoke virtual execute // [{EqualityConstraint}] -> {Null_}
  33[041] - pop 1
  34[089] - return null S2 1
 
@@ -618,27 +618,27 @@ BinaryConstraint.inputs_known tests/type_propagation/deltablue_test.toit
  - argument 1: {LargeInteger_|SmallInteger_}
   0[052] - load local, as class, pop 2 - LargeInteger_(22 - 24) // {True_}
   2[017] - load local 3
-  3[053] - invoke static BinaryConstraint.input tests/type_propagation/deltablue_test.toit // {Variable}
-  6[009] - load field local 48 // {Null_|LargeInteger_|SmallInteger_}
+  3[053] - invoke static BinaryConstraint.input tests/type_propagation/deltablue_test.toit // [{EqualityConstraint|ScaleConstraint}] -> {Variable}
+  6[009] - load field local 48 // [{Variable}] -> {Null_|LargeInteger_|SmallInteger_}
   8[018] - load local 4
-  9[062] - invoke eq // {True_|False_}
+  9[062] - invoke eq // [{Null_|LargeInteger_|SmallInteger_}, {LargeInteger_|SmallInteger_}] -> {True_|False_}
  10[014] - load local 0
  11[081] - branch if true T22
- 14[010] - pop, load field local 80 // {Null_|True_|False_}
+ 14[010] - pop, load field local 80 // [{Variable}] -> {Null_|True_|False_}
  16[014] - load local 0
  17[081] - branch if true T22
- 20[010] - pop, load field local 32 // {Null_|EqualityConstraint|ScaleConstraint|EditConstraint|StayConstraint}
+ 20[010] - pop, load field local 32 // [{Variable}] -> {Null_|EqualityConstraint|ScaleConstraint|EditConstraint|StayConstraint}
  22[048] - as class True_(18 - 20) // {True_|False_}
  24[088] - return S2 2
 
 BinaryConstraint.remove_from_graph tests/type_propagation/deltablue_test.toit
  - argument 0: {EqualityConstraint|ScaleConstraint}
-  0[009] - load field local 18 // {Null_|Variable}
+  0[009] - load field local 18 // [{EqualityConstraint|ScaleConstraint}] -> {Null_|Variable}
   2[017] - load local 3
-  3[053] - invoke static Variable.remove_constraint tests/type_propagation/deltablue_test.toit // {Null_}
-  6[010] - pop, load field local 34 // {Null_|Variable}
+  3[053] - invoke static Variable.remove_constraint tests/type_propagation/deltablue_test.toit // [{Null_|Variable}, {EqualityConstraint|ScaleConstraint}] -> {Null_}
+  6[010] - pop, load field local 34 // [{EqualityConstraint|ScaleConstraint}] -> {Null_|Variable}
   8[017] - load local 3
-  9[053] - invoke static Variable.remove_constraint tests/type_propagation/deltablue_test.toit // {Null_}
+  9[053] - invoke static Variable.remove_constraint tests/type_propagation/deltablue_test.toit // [{Null_|Variable}, {EqualityConstraint|ScaleConstraint}] -> {Null_}
  12[002] - pop, load local S2
  14[025] - load smi 1
  15[048] - as class LargeInteger_(22 - 24) // {True_}
@@ -667,32 +667,32 @@ ScaleConstraint tests/type_propagation/deltablue_test.toit
  22[000] - load local S7
  24[000] - load local S7
  26[000] - load local S7
- 28[053] - invoke static BinaryConstraint tests/type_propagation/deltablue_test.toit // {ScaleConstraint}
+ 28[053] - invoke static BinaryConstraint tests/type_propagation/deltablue_test.toit // [{ScaleConstraint}, {Strength}, {Variable}, {Variable}] -> {ScaleConstraint}
  31[002] - pop, load local S7
  33[088] - return S1 6
 
 ScaleConstraint.add_to_graph tests/type_propagation/deltablue_test.toit
  - argument 0: {ScaleConstraint}
   0[016] - load local 2
-  1[053] - invoke static BinaryConstraint.add_to_graph tests/type_propagation/deltablue_test.toit // {Null_}
-  4[010] - pop, load field local 66 // {Null_|Variable}
+  1[053] - invoke static BinaryConstraint.add_to_graph tests/type_propagation/deltablue_test.toit // [{ScaleConstraint}] -> {Null_}
+  4[010] - pop, load field local 66 // [{ScaleConstraint}] -> {Null_|Variable}
   6[017] - load local 3
-  7[053] - invoke static Variable.add_constraint tests/type_propagation/deltablue_test.toit // {Null_}
- 10[010] - pop, load field local 82 // {Null_|Variable}
+  7[053] - invoke static Variable.add_constraint tests/type_propagation/deltablue_test.toit // [{Null_|Variable}, {ScaleConstraint}] -> {Null_}
+ 10[010] - pop, load field local 82 // [{ScaleConstraint}] -> {Null_|Variable}
  12[017] - load local 3
- 13[053] - invoke static Variable.add_constraint tests/type_propagation/deltablue_test.toit // {Null_}
+ 13[053] - invoke static Variable.add_constraint tests/type_propagation/deltablue_test.toit // [{Null_|Variable}, {ScaleConstraint}] -> {Null_}
  16[089] - return null S1 1
 
 ScaleConstraint.remove_from_graph tests/type_propagation/deltablue_test.toit
  - argument 0: {ScaleConstraint}
   0[016] - load local 2
-  1[053] - invoke static BinaryConstraint.remove_from_graph tests/type_propagation/deltablue_test.toit // {Null_}
-  4[010] - pop, load field local 66 // {Null_|Variable}
+  1[053] - invoke static BinaryConstraint.remove_from_graph tests/type_propagation/deltablue_test.toit // [{ScaleConstraint}] -> {Null_}
+  4[010] - pop, load field local 66 // [{ScaleConstraint}] -> {Null_|Variable}
   6[017] - load local 3
-  7[053] - invoke static Variable.remove_constraint tests/type_propagation/deltablue_test.toit // {Null_}
- 10[010] - pop, load field local 82 // {Null_|Variable}
+  7[053] - invoke static Variable.remove_constraint tests/type_propagation/deltablue_test.toit // [{Null_|Variable}, {ScaleConstraint}] -> {Null_}
+ 10[010] - pop, load field local 82 // [{ScaleConstraint}] -> {Null_|Variable}
  12[017] - load local 3
- 13[053] - invoke static Variable.remove_constraint tests/type_propagation/deltablue_test.toit // {Null_}
+ 13[053] - invoke static Variable.remove_constraint tests/type_propagation/deltablue_test.toit // [{Null_|Variable}, {ScaleConstraint}] -> {Null_}
  16[089] - return null S1 1
 
 ScaleConstraint.mark_inputs tests/type_propagation/deltablue_test.toit
@@ -701,9 +701,9 @@ ScaleConstraint.mark_inputs tests/type_propagation/deltablue_test.toit
   0[052] - load local, as class, pop 2 - LargeInteger_(22 - 24) // {True_}
   2[017] - load local 3
   3[017] - load local 3
-  4[053] - invoke static BinaryConstraint.mark_inputs tests/type_propagation/deltablue_test.toit // {Null_}
-  7[010] - pop, load field local 67 // {Null_|Variable}
-  9[009] - load field local 84 // {Null_|Variable}
+  4[053] - invoke static BinaryConstraint.mark_inputs tests/type_propagation/deltablue_test.toit // [{ScaleConstraint}, {LargeInteger_|SmallInteger_}] -> {Null_}
+  7[010] - pop, load field local 67 // [{ScaleConstraint}] -> {Null_|Variable}
+  9[009] - load field local 84 // [{ScaleConstraint}] -> {Null_|Variable}
  11[018] - load local 4
  12[011] - store field 3
  14[013] - store field, pop 3
@@ -711,31 +711,31 @@ ScaleConstraint.mark_inputs tests/type_propagation/deltablue_test.toit
 
 ScaleConstraint.execute tests/type_propagation/deltablue_test.toit
  - argument 0: {ScaleConstraint}
-  0[009] - load field local 50 // {Null_|SmallInteger_}
+  0[009] - load field local 50 // [{ScaleConstraint}] -> {Null_|SmallInteger_}
   2[026] - load smi 2
-  4[062] - invoke eq // {True_|False_}
+  4[062] - invoke eq // [{Null_|SmallInteger_}, {SmallInteger_}] -> {True_|False_}
   5[082] - branch if false T31
-  8[009] - load field local 34 // {Null_|Variable}
- 10[009] - load field local 19 // {Null_|Variable}
- 12[007] - load field 1 // {Null_|LargeInteger_|SmallInteger_}
- 14[009] - load field local 68 // {Null_|Variable}
- 16[007] - load field 1 // {Null_|LargeInteger_|SmallInteger_}
- 18[075] - invoke mul // {LargeInteger_|SmallInteger_}
- 19[009] - load field local 84 // {Null_|Variable}
- 21[007] - load field 1 // {Null_|LargeInteger_|SmallInteger_}
- 23[073] - invoke add // {LargeInteger_|SmallInteger_}
+  8[009] - load field local 34 // [{ScaleConstraint}] -> {Null_|Variable}
+ 10[009] - load field local 19 // [{ScaleConstraint}] -> {Null_|Variable}
+ 12[007] - load field 1 // [{Null_|Variable}] -> {Null_|LargeInteger_|SmallInteger_}
+ 14[009] - load field local 68 // [{ScaleConstraint}] -> {Null_|Variable}
+ 16[007] - load field 1 // [{Null_|Variable}] -> {Null_|LargeInteger_|SmallInteger_}
+ 18[075] - invoke mul // [{Null_|LargeInteger_|SmallInteger_}, {Null_|LargeInteger_|SmallInteger_}] -> {LargeInteger_|SmallInteger_}
+ 19[009] - load field local 84 // [{ScaleConstraint}] -> {Null_|Variable}
+ 21[007] - load field 1 // [{Null_|Variable}] -> {Null_|LargeInteger_|SmallInteger_}
+ 23[073] - invoke add // [{LargeInteger_|SmallInteger_}, {Null_|LargeInteger_|SmallInteger_}] -> {LargeInteger_|SmallInteger_}
  24[048] - as class LargeInteger_(22 - 24) // {True_}
  26[013] - store field, pop 1
  28[080] - branch T51
- 31[009] - load field local 18 // {Null_|Variable}
- 33[009] - load field local 35 // {Null_|Variable}
- 35[007] - load field 1 // {Null_|LargeInteger_|SmallInteger_}
- 37[009] - load field local 84 // {Null_|Variable}
- 39[007] - load field 1 // {Null_|LargeInteger_|SmallInteger_}
- 41[074] - invoke sub // {LargeInteger_|SmallInteger_}
- 42[009] - load field local 68 // {Null_|Variable}
- 44[007] - load field 1 // {Null_|LargeInteger_|SmallInteger_}
- 46[076] - invoke div // {LargeInteger_|SmallInteger_}
+ 31[009] - load field local 18 // [{ScaleConstraint}] -> {Null_|Variable}
+ 33[009] - load field local 35 // [{ScaleConstraint}] -> {Null_|Variable}
+ 35[007] - load field 1 // [{Null_|Variable}] -> {Null_|LargeInteger_|SmallInteger_}
+ 37[009] - load field local 84 // [{ScaleConstraint}] -> {Null_|Variable}
+ 39[007] - load field 1 // [{Null_|Variable}] -> {Null_|LargeInteger_|SmallInteger_}
+ 41[074] - invoke sub // [{Null_|LargeInteger_|SmallInteger_}, {Null_|LargeInteger_|SmallInteger_}] -> {LargeInteger_|SmallInteger_}
+ 42[009] - load field local 68 // [{ScaleConstraint}] -> {Null_|Variable}
+ 44[007] - load field 1 // [{Null_|Variable}] -> {Null_|LargeInteger_|SmallInteger_}
+ 46[076] - invoke div // [{LargeInteger_|SmallInteger_}, {Null_|LargeInteger_|SmallInteger_}] -> {LargeInteger_|SmallInteger_}
  47[048] - as class LargeInteger_(22 - 24) // {True_}
  49[013] - store field, pop 1
  51[089] - return null S0 1
@@ -743,29 +743,29 @@ ScaleConstraint.execute tests/type_propagation/deltablue_test.toit
 ScaleConstraint.recalculate tests/type_propagation/deltablue_test.toit
  - argument 0: {ScaleConstraint}
   0[016] - load local 2
-  1[053] - invoke static BinaryConstraint.input tests/type_propagation/deltablue_test.toit // {Variable}
+  1[053] - invoke static BinaryConstraint.input tests/type_propagation/deltablue_test.toit // [{ScaleConstraint}] -> {Variable}
   4[017] - load local 3
-  5[053] - invoke static BinaryConstraint.output tests/type_propagation/deltablue_test.toit // {Variable}
+  5[053] - invoke static BinaryConstraint.output tests/type_propagation/deltablue_test.toit // [{ScaleConstraint}] -> {Variable}
   8[014] - load local 0
-  9[009] - load field local 5 // {Null_|Strength}
- 11[009] - load field local 67 // {Null_|Strength}
- 13[053] - invoke static weakest tests/type_propagation/deltablue_test.toit // {Strength}
+  9[009] - load field local 5 // [{ScaleConstraint}] -> {Null_|Strength}
+ 11[009] - load field local 67 // [{Variable}] -> {Null_|Strength}
+ 13[053] - invoke static weakest tests/type_propagation/deltablue_test.toit // [{Null_|Strength}, {Null_|Strength}] -> {Strength}
  16[013] - store field, pop 4
  18[014] - load local 0
- 19[009] - load field local 82 // {Null_|True_|False_}
+ 19[009] - load field local 82 // [{Variable}] -> {Null_|True_|False_}
  21[014] - load local 0
  22[082] - branch if false T37
- 25[010] - pop, load field local 69 // {Null_|Variable}
- 27[007] - load field 5 // {Null_|True_|False_}
+ 25[010] - pop, load field local 69 // [{ScaleConstraint}] -> {Null_|Variable}
+ 27[007] - load field 5 // [{Null_|Variable}] -> {Null_|True_|False_}
  29[014] - load local 0
  30[082] - branch if false T37
- 33[010] - pop, load field local 85 // {Null_|Variable}
- 35[007] - load field 5 // {Null_|True_|False_}
+ 33[010] - pop, load field local 85 // [{ScaleConstraint}] -> {Null_|Variable}
+ 35[007] - load field 5 // [{Null_|Variable}] -> {Null_|True_|False_}
  37[013] - store field, pop 5
- 39[009] - load field local 80 // {Null_|True_|False_}
+ 39[009] - load field local 80 // [{Variable}] -> {Null_|True_|False_}
  41[082] - branch if false T49
  44[018] - load local 4
- 45[053] - invoke static ScaleConstraint.execute tests/type_propagation/deltablue_test.toit // {Null_}
+ 45[053] - invoke static ScaleConstraint.execute tests/type_propagation/deltablue_test.toit // [{ScaleConstraint}] -> {Null_}
  48[041] - pop 1
  49[089] - return null S2 1
 
@@ -781,17 +781,17 @@ EqualityConstraint tests/type_propagation/deltablue_test.toit
   7[019] - load local 5
   8[019] - load local 5
   9[019] - load local 5
- 10[053] - invoke static BinaryConstraint tests/type_propagation/deltablue_test.toit // {EqualityConstraint}
+ 10[053] - invoke static BinaryConstraint tests/type_propagation/deltablue_test.toit // [{EqualityConstraint}, {Strength}, {Variable}, {Variable}] -> {EqualityConstraint}
  13[002] - pop, load local S5
  15[088] - return S1 4
 
 EqualityConstraint.execute tests/type_propagation/deltablue_test.toit
  - argument 0: {EqualityConstraint}
   0[016] - load local 2
-  1[053] - invoke static BinaryConstraint.output tests/type_propagation/deltablue_test.toit // {Variable}
+  1[053] - invoke static BinaryConstraint.output tests/type_propagation/deltablue_test.toit // [{EqualityConstraint}] -> {Variable}
   4[017] - load local 3
-  5[053] - invoke static BinaryConstraint.input tests/type_propagation/deltablue_test.toit // {Variable}
-  8[007] - load field 1 // {Null_|LargeInteger_|SmallInteger_}
+  5[053] - invoke static BinaryConstraint.input tests/type_propagation/deltablue_test.toit // [{EqualityConstraint}] -> {Variable}
+  8[007] - load field 1 // [{Variable}] -> {Null_|LargeInteger_|SmallInteger_}
  10[013] - store field, pop 1
  12[089] - return null S0 1
 
@@ -819,17 +819,17 @@ Variable tests/type_propagation/deltablue_test.toit
  26[018] - load local 4
  27[023] - load smi 0
  28[022] - load null
- 29[053] - invoke static Array_ <sdk>/core/collections.toit // {LargeArray_|SmallArray_}
+ 29[053] - invoke static Array_ <sdk>/core/collections.toit // [{SmallInteger_}, {Null_}] -> {LargeArray_|SmallArray_}
  32[014] - load local 0
  33[004] - store local, pop S1
- 35[053] - invoke static create_list_literal_from_array_ <sdk>/core/collections.toit // {List_}
+ 35[053] - invoke static create_list_literal_from_array_ <sdk>/core/collections.toit // [{LargeArray_|SmallArray_}] -> {List_}
  38[013] - store field, pop 6
  40[018] - load local 4
  41[088] - return S1 3
 
 Variable.value tests/type_propagation/deltablue_test.toit
  - argument 0: {Variable}
-  0[009] - load field local 18 // {Null_|LargeInteger_|SmallInteger_}
+  0[009] - load field local 18 // [{Variable}] -> {Null_|LargeInteger_|SmallInteger_}
   2[088] - return S1 1
 
 Variable.value= tests/type_propagation/deltablue_test.toit
@@ -843,12 +843,12 @@ Variable.value= tests/type_propagation/deltablue_test.toit
 
 Variable.determined_by tests/type_propagation/deltablue_test.toit
  - argument 0: {Variable}
-  0[009] - load field local 34 // {Null_|EqualityConstraint|ScaleConstraint|EditConstraint|StayConstraint}
+  0[009] - load field local 34 // [{Variable}] -> {Null_|EqualityConstraint|ScaleConstraint|EditConstraint|StayConstraint}
   2[088] - return S1 1
 
 Variable.mark tests/type_propagation/deltablue_test.toit
  - argument 0: {Variable}
-  0[009] - load field local 50 // {Null_|LargeInteger_|SmallInteger_}
+  0[009] - load field local 50 // [{Variable}] -> {Null_|LargeInteger_|SmallInteger_}
   2[088] - return S1 1
 
 Variable.mark= tests/type_propagation/deltablue_test.toit
@@ -861,32 +861,32 @@ Variable.mark= tests/type_propagation/deltablue_test.toit
 
 Variable.constraints tests/type_propagation/deltablue_test.toit
  - argument 0: {Variable}
-  0[009] - load field local 98 // {Null_|List_}
+  0[009] - load field local 98 // [{Variable}] -> {Null_|List_}
   2[088] - return S1 1
 
 Variable.add_constraint tests/type_propagation/deltablue_test.toit
  - argument 0: {Variable}
  - argument 1: {EqualityConstraint|ScaleConstraint|EditConstraint|StayConstraint}
   0[052] - load local, as class, pop 2 - EqualityConstraint(43 - 47) // {True_}
-  2[009] - load field local 99 // {Null_|List_}
+  2[009] - load field local 99 // [{Variable}] -> {Null_|List_}
   4[017] - load local 3
-  5[058] - invoke virtual add // {Null_}
+  5[058] - invoke virtual add // [{Null_|List_}, {EqualityConstraint|ScaleConstraint|EditConstraint|StayConstraint}] -> {Null_}
   9[089] - return null S1 2
 
 Variable.remove_constraint tests/type_propagation/deltablue_test.toit
  - argument 0: {Variable}
  - argument 1: {EqualityConstraint|ScaleConstraint|EditConstraint|StayConstraint}
   0[052] - load local, as class, pop 2 - EqualityConstraint(43 - 47) // {True_}
-  2[009] - load field local 99 // {Null_|List_}
+  2[009] - load field local 99 // [{Variable}] -> {Null_|List_}
   4[029] - load [block] in Variable.remove_constraint tests/type_propagation/deltablue_test.toit
   9[015] - load local 1
  10[038] - load block 1
  12[020] - load literal true
- 14[058] - invoke virtual filter // {List_}
+ 14[058] - invoke virtual filter // [{Null_|List_}, [block], {True_}] -> {List_}
  18[040] - pop 3
- 20[009] - load field local 35 // {Null_|EqualityConstraint|ScaleConstraint|EditConstraint|StayConstraint}
+ 20[009] - load field local 35 // [{Variable}] -> {Null_|EqualityConstraint|ScaleConstraint|EditConstraint|StayConstraint}
  22[017] - load local 3
- 23[062] - invoke eq // {True_|False_}
+ 23[062] - invoke eq // [{Null_|EqualityConstraint|ScaleConstraint|EditConstraint|StayConstraint}, {EqualityConstraint|ScaleConstraint|EditConstraint|StayConstraint}] -> {True_|False_}
  24[082] - branch if false T31
  27[017] - load local 3
  28[022] - load null
@@ -899,7 +899,7 @@ Variable.remove_constraint tests/type_propagation/deltablue_test.toit
   0[016] - load local 2
   1[018] - load local 4
   2[005] - load outer S4 // {EqualityConstraint|ScaleConstraint|EditConstraint|StayConstraint}
-  4[062] - invoke eq // {True_|False_}
+  4[062] - invoke eq // [{*}, {EqualityConstraint|ScaleConstraint|EditConstraint|StayConstraint}] -> {True_|False_}
   5[081] - branch if true T13
   8[020] - load literal true
  10[080] - branch T15
@@ -919,15 +919,15 @@ Planner.incremental_add tests/type_propagation/deltablue_test.toit
  - argument 1: {*}
   0[052] - load local, as class, pop 2 - EqualityConstraint(43 - 47) // {True_|False_}
   2[017] - load local 3
-  3[053] - invoke static Planner.new_mark tests/type_propagation/deltablue_test.toit // {LargeInteger_|SmallInteger_}
+  3[053] - invoke static Planner.new_mark tests/type_propagation/deltablue_test.toit // [{Planner}] -> {LargeInteger_|SmallInteger_}
   6[017] - load local 3
   7[015] - load local 1
-  8[053] - invoke static Constraint.satisfy tests/type_propagation/deltablue_test.toit // {Null_|EqualityConstraint|ScaleConstraint|EditConstraint|StayConstraint}
+  8[053] - invoke static Constraint.satisfy tests/type_propagation/deltablue_test.toit // [{EqualityConstraint|ScaleConstraint|EditConstraint|StayConstraint}, {LargeInteger_|SmallInteger_}] -> {Null_|EqualityConstraint|ScaleConstraint|EditConstraint|StayConstraint}
  11[014] - load local 0
  12[082] - branch if false T28
  15[014] - load local 0
  16[016] - load local 2
- 17[058] - invoke virtual satisfy // {Null_|EqualityConstraint|ScaleConstraint|EditConstraint|StayConstraint}
+ 17[058] - invoke virtual satisfy // [{Null_|EqualityConstraint|ScaleConstraint|EditConstraint|StayConstraint}, {LargeInteger_|SmallInteger_}] -> {Null_|EqualityConstraint|ScaleConstraint|EditConstraint|StayConstraint}
  21[004] - store local, pop S1
  23[083] - branch back T11
  28[089] - return null S2 2
@@ -937,26 +937,26 @@ Planner.incremental_remove tests/type_propagation/deltablue_test.toit
  - argument 1: {EqualityConstraint|ScaleConstraint|EditConstraint|StayConstraint}
   0[052] - load local, as class, pop 2 - EqualityConstraint(43 - 47) // {True_}
   2[016] - load local 2
-  3[058] - invoke virtual output // {Null_|Variable}
+  3[058] - invoke virtual output // [{EqualityConstraint|ScaleConstraint|EditConstraint|StayConstraint}] -> {Null_|Variable}
   7[017] - load local 3
-  8[058] - invoke virtual mark_unsatisfied // {Null_}
+  8[058] - invoke virtual mark_unsatisfied // [{EqualityConstraint|ScaleConstraint|EditConstraint|StayConstraint}] -> {Null_}
  12[002] - pop, load local S3
- 14[058] - invoke virtual remove_from_graph // {Null_}
+ 14[058] - invoke virtual remove_from_graph // [{EqualityConstraint|ScaleConstraint|EditConstraint|StayConstraint}] -> {Null_}
  18[002] - pop, load local S4
  20[015] - load local 1
- 21[053] - invoke static Planner.remove_propagate_from tests/type_propagation/deltablue_test.toit // {List_}
+ 21[053] - invoke static Planner.remove_propagate_from tests/type_propagation/deltablue_test.toit // [{Planner}, {Null_|Variable}] -> {List_}
  24[033] - load global var lazy G0 // {Strength}
  26[029] - load [block] in Planner.incremental_remove tests/type_propagation/deltablue_test.toit
  31[016] - load local 2
  32[038] - load block 1
- 34[058] - invoke virtual do // {Null_}
+ 34[058] - invoke virtual do // [{List_}, [block]] -> {Null_}
  38[041] - pop 1
  39[002] - pop, load local S0
- 41[058] - invoke virtual next_weaker // {Strength}
+ 41[058] - invoke virtual next_weaker // [{Strength}] -> {Strength}
  45[004] - store local, pop S1
  47[014] - load local 0
  48[033] - load global var lazy G6 // {Strength}
- 50[062] - invoke eq // {True_|False_}
+ 50[062] - invoke eq // [{Strength}, {Strength}] -> {True_|False_}
  51[082] - branch if false T57
  54[080] - branch T62
  57[083] - branch back T26
@@ -967,23 +967,23 @@ Planner.incremental_remove tests/type_propagation/deltablue_test.toit
  - argument 1: {*}
   0[022] - load null
   1[017] - load local 3
-  2[060] - invoke virtual get strength // {Null_|Strength}
+  2[060] - invoke virtual get strength // [{*}] -> {Null_|Strength}
   5[019] - load local 5
   6[005] - load outer S1 // {Strength}
-  8[062] - invoke eq // {True_|False_}
+  8[062] - invoke eq // [{Null_|Strength}, {Strength}] -> {True_|False_}
   9[082] - branch if false T20
  12[002] - pop, load local S3
  14[005] - load outer S7 // {Planner}
  16[017] - load local 3
- 17[053] - invoke static Planner.incremental_add tests/type_propagation/deltablue_test.toit // {Null_}
+ 17[053] - invoke static Planner.incremental_add tests/type_propagation/deltablue_test.toit // [{Planner}, {*}] -> {Null_}
  20[088] - return S1 2
 
 Planner.new_mark tests/type_propagation/deltablue_test.toit
  - argument 0: {Planner}
   0[016] - load local 2
-  1[009] - load field local 3 // {Null_|LargeInteger_|SmallInteger_}
+  1[009] - load field local 3 // [{Planner}] -> {Null_|LargeInteger_|SmallInteger_}
   3[025] - load smi 1
-  4[073] - invoke add // {LargeInteger_|SmallInteger_}
+  4[073] - invoke add // [{Null_|LargeInteger_|SmallInteger_}, {SmallInteger_}] -> {LargeInteger_|SmallInteger_}
   5[011] - store field 0
   7[048] - as class LargeInteger_(22 - 24) // {True_}
   9[088] - return S1 1
@@ -993,37 +993,37 @@ Planner.make_plan tests/type_propagation/deltablue_test.toit
  - argument 1: {List_}
   0[052] - load local, as class, pop 2 - List_(36 - 40) // {True_}
   2[017] - load local 3
-  3[053] - invoke static Planner.new_mark tests/type_propagation/deltablue_test.toit // {LargeInteger_|SmallInteger_}
+  3[053] - invoke static Planner.new_mark tests/type_propagation/deltablue_test.toit // [{Planner}] -> {LargeInteger_|SmallInteger_}
   6[042] - allocate instance Plan
-  8[053] - invoke static Plan tests/type_propagation/deltablue_test.toit // {Plan}
+  8[053] - invoke static Plan tests/type_propagation/deltablue_test.toit // [{Plan}] -> {Plan}
  11[018] - load local 4
  12[014] - load local 0
- 13[053] - invoke static CollectionBase.is_empty <sdk>/core/collections.toit // {True_|False_}
+ 13[053] - invoke static CollectionBase.is_empty <sdk>/core/collections.toit // [{List_}] -> {True_|False_}
  16[081] - branch if true T79
  19[014] - load local 0
- 20[058] - invoke virtual remove_last // {*}
+ 20[058] - invoke virtual remove_last // [{List_}] -> {*}
  24[014] - load local 0
- 25[058] - invoke virtual output // {Null_|Variable}
- 29[060] - invoke virtual get mark // {Null_|LargeInteger_|SmallInteger_}
+ 25[058] - invoke virtual output // [{*}] -> {Null_|Variable}
+ 29[060] - invoke virtual get mark // [{Null_|Variable}] -> {Null_|LargeInteger_|SmallInteger_}
  32[018] - load local 4
- 33[062] - invoke eq // {True_|False_}
+ 33[062] - invoke eq // [{Null_|LargeInteger_|SmallInteger_}, {LargeInteger_|SmallInteger_}] -> {True_|False_}
  34[081] - branch if true T73
  37[014] - load local 0
  38[018] - load local 4
- 39[058] - invoke virtual inputs_known // {True_|False_}
+ 39[058] - invoke virtual inputs_known // [{*}, {LargeInteger_|SmallInteger_}] -> {True_|False_}
  43[082] - branch if false T73
  46[016] - load local 2
  47[015] - load local 1
- 48[053] - invoke static Plan.add_constraint tests/type_propagation/deltablue_test.toit // {Null_}
+ 48[053] - invoke static Plan.add_constraint tests/type_propagation/deltablue_test.toit // [{Plan}, {*}] -> {Null_}
  51[002] - pop, load local S0
- 53[058] - invoke virtual output // {Null_|Variable}
+ 53[058] - invoke virtual output // [{*}] -> {Null_|Variable}
  57[018] - load local 4
- 58[061] - invoke virtual set mark // {LargeInteger_|SmallInteger_}
+ 58[061] - invoke virtual set mark // [{Null_|Variable}, {LargeInteger_|SmallInteger_}] -> {LargeInteger_|SmallInteger_}
  61[002] - pop, load local S7
  63[015] - load local 1
- 64[058] - invoke virtual output // {Null_|Variable}
+ 64[058] - invoke virtual output // [{*}] -> {Null_|Variable}
  68[017] - load local 3
- 69[053] - invoke static Planner.add_constraints_consuming_to tests/type_propagation/deltablue_test.toit // {Null_}
+ 69[053] - invoke static Planner.add_constraints_consuming_to tests/type_propagation/deltablue_test.toit // [{Planner}, {Null_|Variable}, {List_}] -> {Null_}
  72[041] - pop 1
  73[041] - pop 1
  74[083] - branch back T12
@@ -1036,18 +1036,18 @@ Planner.extract_plan_from_constraints tests/type_propagation/deltablue_test.toit
   0[052] - load local, as class, pop 2 - List_(36 - 40) // {True_}
   2[023] - load smi 0
   3[022] - load null
-  4[053] - invoke static Array_ <sdk>/core/collections.toit // {LargeArray_|SmallArray_}
+  4[053] - invoke static Array_ <sdk>/core/collections.toit // [{SmallInteger_}, {Null_}] -> {LargeArray_|SmallArray_}
   7[014] - load local 0
   8[004] - store local, pop S1
- 10[053] - invoke static create_list_literal_from_array_ <sdk>/core/collections.toit // {List_}
+ 10[053] - invoke static create_list_literal_from_array_ <sdk>/core/collections.toit // [{LargeArray_|SmallArray_}] -> {List_}
  13[029] - load [block] in Planner.extract_plan_from_constraints tests/type_propagation/deltablue_test.toit
  18[018] - load local 4
  19[038] - load block 1
- 21[058] - invoke virtual do // {Null_}
+ 21[058] - invoke virtual do // [{List_}, [block]] -> {Null_}
  25[041] - pop 1
  26[002] - pop, load local S4
  28[015] - load local 1
- 29[053] - invoke static Planner.make_plan tests/type_propagation/deltablue_test.toit // {Plan}
+ 29[053] - invoke static Planner.make_plan tests/type_propagation/deltablue_test.toit // [{Planner}, {List_}] -> {Plan}
  32[088] - return S2 2
 
 [block] in Planner.extract_plan_from_constraints tests/type_propagation/deltablue_test.toit
@@ -1055,15 +1055,15 @@ Planner.extract_plan_from_constraints tests/type_propagation/deltablue_test.toit
  - argument 1: {*}
   0[022] - load null
   1[017] - load local 3
-  2[058] - invoke virtual is_input // {True_|False_}
+  2[058] - invoke virtual is_input // [{*}] -> {True_|False_}
   6[082] - branch if false T24
   9[017] - load local 3
- 10[060] - invoke virtual get is_satisfied // {Null_|True_|False_}
+ 10[060] - invoke virtual get is_satisfied // [{*}] -> {Null_|True_|False_}
  13[082] - branch if false T24
  16[002] - pop, load local S3
  18[005] - load outer S1 // {List_}
  20[017] - load local 3
- 21[053] - invoke static List.add <sdk>/core/collections.toit // {Null_}
+ 21[053] - invoke static List.add <sdk>/core/collections.toit // [{List_}, {*}] -> {Null_}
  24[088] - return S1 2
 
 Planner.add_propagate tests/type_propagation/deltablue_test.toit
@@ -1073,33 +1073,33 @@ Planner.add_propagate tests/type_propagation/deltablue_test.toit
   0[052] - load local, as class, pop 3 - EqualityConstraint(43 - 47) // {True_}
   2[052] - load local, as class, pop 2 - LargeInteger_(22 - 24) // {True_}
   4[017] - load local 3
-  5[053] - invoke static create_array_ <sdk>/core/collections.toit // {LargeArray_|SmallArray_}
-  8[053] - invoke static create_list_literal_from_array_ <sdk>/core/collections.toit // {List_}
+  5[053] - invoke static create_array_ <sdk>/core/collections.toit // [{EqualityConstraint|ScaleConstraint|EditConstraint|StayConstraint}] -> {LargeArray_|SmallArray_}
+  8[053] - invoke static create_list_literal_from_array_ <sdk>/core/collections.toit // [{LargeArray_|SmallArray_}] -> {List_}
  11[014] - load local 0
- 12[053] - invoke static CollectionBase.is_empty <sdk>/core/collections.toit // {True_|False_}
+ 12[053] - invoke static CollectionBase.is_empty <sdk>/core/collections.toit // [{List_}] -> {True_|False_}
  15[081] - branch if true T74
  18[014] - load local 0
- 19[058] - invoke virtual remove_last // {*}
+ 19[058] - invoke virtual remove_last // [{List_}] -> {*}
  23[014] - load local 0
- 24[058] - invoke virtual output // {Null_|Variable}
- 28[060] - invoke virtual get mark // {Null_|LargeInteger_|SmallInteger_}
+ 24[058] - invoke virtual output // [{*}] -> {Null_|Variable}
+ 28[060] - invoke virtual get mark // [{Null_|Variable}] -> {Null_|LargeInteger_|SmallInteger_}
  31[019] - load local 5
- 32[062] - invoke eq // {True_|False_}
+ 32[062] - invoke eq // [{Null_|LargeInteger_|SmallInteger_}, {LargeInteger_|SmallInteger_}] -> {True_|False_}
  33[082] - branch if false T51
  36[000] - load local S6
  38[000] - load local S6
- 40[053] - invoke static Planner.incremental_remove tests/type_propagation/deltablue_test.toit // {Null_}
+ 40[053] - invoke static Planner.incremental_remove tests/type_propagation/deltablue_test.toit // [{Planner}, {EqualityConstraint|ScaleConstraint|EditConstraint|StayConstraint}] -> {Null_}
  43[041] - pop 1
  44[020] - load literal false
  46[048] - as class True_(18 - 20) // {True_}
  48[088] - return S3 3
  51[014] - load local 0
- 52[058] - invoke virtual recalculate // {Null_}
+ 52[058] - invoke virtual recalculate // [{*}] -> {Null_}
  56[002] - pop, load local S6
  58[015] - load local 1
- 59[058] - invoke virtual output // {Null_|Variable}
+ 59[058] - invoke virtual output // [{*}] -> {Null_|Variable}
  63[017] - load local 3
- 64[053] - invoke static Planner.add_constraints_consuming_to tests/type_propagation/deltablue_test.toit // {Null_}
+ 64[053] - invoke static Planner.add_constraints_consuming_to tests/type_propagation/deltablue_test.toit // [{Planner}, {Null_|Variable}, {List_}] -> {Null_}
  67[040] - pop 2
  69[083] - branch back T11
  74[020] - load literal true
@@ -1121,31 +1121,31 @@ Planner.remove_propagate_from tests/type_propagation/deltablue_test.toit
  14[013] - store field, pop 5
  16[023] - load smi 0
  17[022] - load null
- 18[053] - invoke static Array_ <sdk>/core/collections.toit // {LargeArray_|SmallArray_}
+ 18[053] - invoke static Array_ <sdk>/core/collections.toit // [{SmallInteger_}, {Null_}] -> {LargeArray_|SmallArray_}
  21[014] - load local 0
  22[004] - store local, pop S1
- 24[053] - invoke static create_list_literal_from_array_ <sdk>/core/collections.toit // {List_}
+ 24[053] - invoke static create_list_literal_from_array_ <sdk>/core/collections.toit // [{LargeArray_|SmallArray_}] -> {List_}
  27[017] - load local 3
- 28[053] - invoke static create_array_ <sdk>/core/collections.toit // {LargeArray_|SmallArray_}
- 31[053] - invoke static create_list_literal_from_array_ <sdk>/core/collections.toit // {List_}
+ 28[053] - invoke static create_array_ <sdk>/core/collections.toit // [{Variable}] -> {LargeArray_|SmallArray_}
+ 31[053] - invoke static create_list_literal_from_array_ <sdk>/core/collections.toit // [{LargeArray_|SmallArray_}] -> {List_}
  34[014] - load local 0
- 35[053] - invoke static CollectionBase.is_empty <sdk>/core/collections.toit // {True_|False_}
+ 35[053] - invoke static CollectionBase.is_empty <sdk>/core/collections.toit // [{List_}] -> {True_|False_}
  38[081] - branch if true T89
  41[014] - load local 0
- 42[058] - invoke virtual remove_last // {*}
+ 42[058] - invoke virtual remove_last // [{List_}] -> {*}
  46[029] - load [block] in Planner.remove_propagate_from tests/type_propagation/deltablue_test.toit
  51[015] - load local 1
- 52[060] - invoke virtual get constraints // {Null_|List_}
+ 52[060] - invoke virtual get constraints // [{*}] -> {Null_|List_}
  55[038] - load block 1
- 57[058] - invoke virtual do // {Null_}
+ 57[058] - invoke virtual do // [{Null_|List_}, [block]] -> {Null_}
  61[041] - pop 1
  62[002] - pop, load local S0
- 64[060] - invoke virtual get determined_by // {Null_|EqualityConstraint|ScaleConstraint|EditConstraint|StayConstraint}
+ 64[060] - invoke virtual get determined_by // [{*}] -> {Null_|EqualityConstraint|ScaleConstraint|EditConstraint|StayConstraint}
  67[029] - load [block] in Planner.remove_propagate_from tests/type_propagation/deltablue_test.toit
  72[016] - load local 2
- 73[060] - invoke virtual get constraints // {Null_|List_}
+ 73[060] - invoke virtual get constraints // [{*}] -> {Null_|List_}
  76[038] - load block 1
- 78[058] - invoke virtual do // {Null_}
+ 78[058] - invoke virtual do // [{Null_|List_}, [block]] -> {Null_}
  82[040] - pop 4
  84[083] - branch back T34
  89[015] - load local 1
@@ -1156,12 +1156,12 @@ Planner.remove_propagate_from tests/type_propagation/deltablue_test.toit
  - argument 1: {*}
   0[022] - load null
   1[017] - load local 3
-  2[060] - invoke virtual get is_satisfied // {Null_|True_|False_}
+  2[060] - invoke virtual get is_satisfied // [{*}] -> {Null_|True_|False_}
   5[081] - branch if true T16
   8[002] - pop, load local S3
  10[005] - load outer S3 // {List_}
  12[017] - load local 3
- 13[053] - invoke static List.add <sdk>/core/collections.toit // {Null_}
+ 13[053] - invoke static List.add <sdk>/core/collections.toit // [{List_}, {*}] -> {Null_}
  16[088] - return S1 2
 
 [block] in Planner.remove_propagate_from tests/type_propagation/deltablue_test.toit
@@ -1171,18 +1171,18 @@ Planner.remove_propagate_from tests/type_propagation/deltablue_test.toit
   1[017] - load local 3
   2[019] - load local 5
   3[005] - load outer S1 // {Null_|EqualityConstraint|ScaleConstraint|EditConstraint|StayConstraint}
-  5[062] - invoke eq // {True_|False_}
+  5[062] - invoke eq // [{*}, {Null_|EqualityConstraint|ScaleConstraint|EditConstraint|StayConstraint}] -> {True_|False_}
   6[081] - branch if true T34
   9[017] - load local 3
- 10[060] - invoke virtual get is_satisfied // {Null_|True_|False_}
+ 10[060] - invoke virtual get is_satisfied // [{*}] -> {Null_|True_|False_}
  13[082] - branch if false T34
  16[002] - pop, load local S2
- 18[058] - invoke virtual recalculate // {Null_}
+ 18[058] - invoke virtual recalculate // [{*}] -> {Null_}
  22[002] - pop, load local S3
  24[005] - load outer S3 // {List_}
  26[017] - load local 3
- 27[058] - invoke virtual output // {Null_|Variable}
- 31[053] - invoke static List.add <sdk>/core/collections.toit // {Null_}
+ 27[058] - invoke virtual output // [{*}] -> {Null_|Variable}
+ 31[053] - invoke static List.add <sdk>/core/collections.toit // [{List_}, {Null_|Variable}] -> {Null_}
  34[088] - return S1 2
 
 Planner.add_constraints_consuming_to tests/type_propagation/deltablue_test.toit
@@ -1191,11 +1191,11 @@ Planner.add_constraints_consuming_to tests/type_propagation/deltablue_test.toit
  - argument 2: {List_}
   0[052] - load local, as class, pop 3 - Variable(42 - 43) // {True_|False_}
   2[052] - load local, as class, pop 2 - List_(36 - 40) // {True_}
-  4[009] - load field local 35 // {Null_|EqualityConstraint|ScaleConstraint|EditConstraint|StayConstraint}
+  4[009] - load field local 35 // [{Variable}] -> {Null_|EqualityConstraint|ScaleConstraint|EditConstraint|StayConstraint}
   6[029] - load [block] in Planner.add_constraints_consuming_to tests/type_propagation/deltablue_test.toit
- 11[009] - load field local 101 // {Null_|List_}
+ 11[009] - load field local 101 // [{Variable}] -> {Null_|List_}
  13[038] - load block 1
- 15[058] - invoke virtual do // {Null_}
+ 15[058] - invoke virtual do // [{Null_|List_}, [block]] -> {Null_}
  19[089] - return null S3 3
 
 [block] in Planner.add_constraints_consuming_to tests/type_propagation/deltablue_test.toit
@@ -1205,15 +1205,15 @@ Planner.add_constraints_consuming_to tests/type_propagation/deltablue_test.toit
   1[017] - load local 3
   2[019] - load local 5
   3[005] - load outer S1 // {Null_|EqualityConstraint|ScaleConstraint|EditConstraint|StayConstraint}
-  5[062] - invoke eq // {True_|False_}
+  5[062] - invoke eq // [{*}, {Null_|EqualityConstraint|ScaleConstraint|EditConstraint|StayConstraint}] -> {True_|False_}
   6[081] - branch if true T24
   9[017] - load local 3
- 10[060] - invoke virtual get is_satisfied // {Null_|True_|False_}
+ 10[060] - invoke virtual get is_satisfied // [{*}] -> {Null_|True_|False_}
  13[082] - branch if false T24
  16[002] - pop, load local S3
  18[005] - load outer S4 // {List_}
  20[017] - load local 3
- 21[053] - invoke static List.add <sdk>/core/collections.toit // {Null_}
+ 21[053] - invoke static List.add <sdk>/core/collections.toit // [{List_}, {*}] -> {Null_}
  24[088] - return S1 2
 
 Plan tests/type_propagation/deltablue_test.toit
@@ -1221,10 +1221,10 @@ Plan tests/type_propagation/deltablue_test.toit
   0[016] - load local 2
   1[023] - load smi 0
   2[022] - load null
-  3[053] - invoke static Array_ <sdk>/core/collections.toit // {LargeArray_|SmallArray_}
+  3[053] - invoke static Array_ <sdk>/core/collections.toit // [{SmallInteger_}, {Null_}] -> {LargeArray_|SmallArray_}
   6[014] - load local 0
   7[004] - store local, pop S1
-  9[053] - invoke static create_list_literal_from_array_ <sdk>/core/collections.toit // {List_}
+  9[053] - invoke static create_list_literal_from_array_ <sdk>/core/collections.toit // [{LargeArray_|SmallArray_}] -> {List_}
  12[013] - store field, pop 0
  14[016] - load local 2
  15[088] - return S1 1
@@ -1233,31 +1233,31 @@ Plan.add_constraint tests/type_propagation/deltablue_test.toit
  - argument 0: {Plan}
  - argument 1: {*}
   0[052] - load local, as class, pop 2 - EqualityConstraint(43 - 47) // {True_|False_}
-  2[009] - load field local 3 // {Null_|List_}
+  2[009] - load field local 3 // [{Plan}] -> {Null_|List_}
   4[017] - load local 3
-  5[053] - invoke static List.add <sdk>/core/collections.toit // {Null_}
+  5[053] - invoke static List.add <sdk>/core/collections.toit // [{Null_|List_}, {EqualityConstraint|ScaleConstraint|EditConstraint|StayConstraint}] -> {Null_}
   8[089] - return null S1 2
 
 Plan.execute tests/type_propagation/deltablue_test.toit
  - argument 0: {Plan}
   0[029] - load [block] in Plan.execute tests/type_propagation/deltablue_test.toit
-  5[009] - load field local 3 // {Null_|List_}
+  5[009] - load field local 3 // [{Plan}] -> {Null_|List_}
   7[038] - load block 1
-  9[058] - invoke virtual do // {Null_}
+  9[058] - invoke virtual do // [{Null_|List_}, [block]] -> {Null_}
  13[089] - return null S2 1
 
 [block] in Plan.execute tests/type_propagation/deltablue_test.toit
  - argument 0: [block]
  - argument 1: {*}
   0[016] - load local 2
-  1[058] - invoke virtual execute // {Null_}
+  1[058] - invoke virtual execute // [{*}] -> {Null_}
   5[088] - return S1 2
 
 chain_test tests/type_propagation/deltablue_test.toit
  - argument 0: {SmallInteger_}
   0[052] - load local, as class, pop 2 - LargeInteger_(22 - 24) // {True_}
   2[042] - allocate instance Planner
-  4[053] - invoke static Planner tests/type_propagation/deltablue_test.toit // {Planner}
+  4[053] - invoke static Planner tests/type_propagation/deltablue_test.toit // [{Planner}] -> {Planner}
   7[035] - store global var G7
   9[041] - pop 1
  10[022] - load null
@@ -1266,32 +1266,32 @@ chain_test tests/type_propagation/deltablue_test.toit
  13[023] - load smi 0
  14[014] - load local 0
  15[000] - load local S7
- 17[065] - invoke lte // {True_|False_}
+ 17[065] - invoke lte // [{LargeInteger_|SmallInteger_}, {SmallInteger_}] -> {True_|False_}
  18[082] - branch if false T85
  21[042] - allocate instance Variable
  23[020] - load literal v
  25[016] - load local 2
- 26[058] - invoke virtual stringify // {String_}
- 30[073] - invoke add // {String_}
+ 26[058] - invoke virtual stringify // [{LargeInteger_|SmallInteger_}] -> {String_}
+ 30[073] - invoke add // [{String_}, {String_}] -> {String_}
  31[023] - load smi 0
- 32[053] - invoke static Variable tests/type_propagation/deltablue_test.toit // {Variable}
+ 32[053] - invoke static Variable tests/type_propagation/deltablue_test.toit // [{Variable}, {String_}, {SmallInteger_}] -> {Variable}
  35[018] - load local 4
  36[082] - branch if false T50
  39[042] - allocate instance EqualityConstraint
  41[033] - load global var lazy G0 // {Strength}
  43[000] - load local S6
  45[017] - load local 3
- 46[053] - invoke static EqualityConstraint tests/type_propagation/deltablue_test.toit // {EqualityConstraint}
+ 46[053] - invoke static EqualityConstraint tests/type_propagation/deltablue_test.toit // [{EqualityConstraint}, {Strength}, {Null_|Variable}, {Variable}] -> {EqualityConstraint}
  49[041] - pop 1
  50[015] - load local 1
  51[023] - load smi 0
- 52[062] - invoke eq // {True_|False_}
+ 52[062] - invoke eq // [{LargeInteger_|SmallInteger_}, {SmallInteger_}] -> {True_|False_}
  53[082] - branch if false T59
  56[014] - load local 0
  57[004] - store local, pop S4
  59[015] - load local 1
  60[000] - load local S8
- 62[062] - invoke eq // {True_|False_}
+ 62[062] - invoke eq // [{LargeInteger_|SmallInteger_}, {SmallInteger_}] -> {True_|False_}
  63[082] - branch if false T69
  66[014] - load local 0
  67[004] - store local, pop S3
@@ -1301,7 +1301,7 @@ chain_test tests/type_propagation/deltablue_test.toit
  73[014] - load local 0
  74[014] - load local 0
  75[025] - load smi 1
- 76[073] - invoke add // {LargeInteger_|SmallInteger_}
+ 76[073] - invoke add // [{LargeInteger_|SmallInteger_}, {SmallInteger_}] -> {LargeInteger_|SmallInteger_}
  77[004] - store local, pop S2
  79[041] - pop 1
  80[083] - branch back T14
@@ -1309,65 +1309,65 @@ chain_test tests/type_propagation/deltablue_test.toit
  86[042] - allocate instance StayConstraint
  88[033] - load global var lazy G3 // {Strength}
  90[016] - load local 2
- 91[053] - invoke static StayConstraint tests/type_propagation/deltablue_test.toit // {StayConstraint}
+ 91[053] - invoke static StayConstraint tests/type_propagation/deltablue_test.toit // [{StayConstraint}, {Strength}, {Null_|Variable}] -> {StayConstraint}
  94[041] - pop 1
  95[042] - allocate instance EditConstraint
  97[033] - load global var lazy G2 // {Strength}
  99[017] - load local 3
-100[053] - invoke static EditConstraint tests/type_propagation/deltablue_test.toit // {EditConstraint}
+100[053] - invoke static EditConstraint tests/type_propagation/deltablue_test.toit // [{EditConstraint}, {Strength}, {Null_|Variable}] -> {EditConstraint}
 103[030] - load global var G7 // {Null_|Planner}
 105[015] - load local 1
-106[053] - invoke static create_array_ <sdk>/core/collections.toit // {LargeArray_|SmallArray_}
-109[053] - invoke static create_list_literal_from_array_ <sdk>/core/collections.toit // {List_}
-112[058] - invoke virtual extract_plan_from_constraints // {Plan}
+106[053] - invoke static create_array_ <sdk>/core/collections.toit // [{EditConstraint}] -> {LargeArray_|SmallArray_}
+109[053] - invoke static create_list_literal_from_array_ <sdk>/core/collections.toit // [{LargeArray_|SmallArray_}] -> {List_}
+112[058] - invoke virtual extract_plan_from_constraints // [{Null_|Planner}, {List_}] -> {Plan}
 116[023] - load smi 0
 117[014] - load local 0
 118[026] - load smi 100
-120[063] - invoke lt // {True_|False_}
+120[063] - invoke lt // [{LargeInteger_|SmallInteger_}, {SmallInteger_}] -> {True_|False_}
 121[082] - branch if false T207
 124[018] - load local 4
 125[015] - load local 1
-126[061] - invoke virtual set value // {LargeInteger_|SmallInteger_}
+126[061] - invoke virtual set value // [{Null_|Variable}, {LargeInteger_|SmallInteger_}] -> {LargeInteger_|SmallInteger_}
 129[002] - pop, load local S1
-131[053] - invoke static Plan.execute tests/type_propagation/deltablue_test.toit // {Null_}
+131[053] - invoke static Plan.execute tests/type_propagation/deltablue_test.toit // [{Plan}] -> {Null_}
 134[002] - pop, load local S3
-136[060] - invoke virtual get value // {Null_|LargeInteger_|SmallInteger_}
+136[060] - invoke virtual get value // [{Null_|Variable}] -> {Null_|LargeInteger_|SmallInteger_}
 139[015] - load local 1
-140[062] - invoke eq // {True_|False_}
+140[062] - invoke eq // [{Null_|LargeInteger_|SmallInteger_}, {LargeInteger_|SmallInteger_}] -> {True_|False_}
 141[081] - branch if true T195
 144[026] - load smi 5
 146[022] - load null
-147[053] - invoke static Array_ <sdk>/core/collections.toit // {LargeArray_|SmallArray_}
+147[053] - invoke static Array_ <sdk>/core/collections.toit // [{SmallInteger_}, {Null_}] -> {LargeArray_|SmallArray_}
 150[014] - load local 0
 151[023] - load smi 0
 152[020] - load literal Chain test failed: 
-154[079] - invoke at_put // {*}
+154[079] - invoke at_put // [{LargeArray_|SmallArray_}, {SmallInteger_}, {String_}] -> {*}
 155[002] - pop, load local S0
 157[025] - load smi 1
 158[000] - load local S6
-160[060] - invoke virtual get value // {Null_|LargeInteger_|SmallInteger_}
-163[079] - invoke at_put // {*}
+160[060] - invoke virtual get value // [{Null_|Variable}] -> {Null_|LargeInteger_|SmallInteger_}
+163[079] - invoke at_put // [{LargeArray_|SmallArray_}, {SmallInteger_}, {Null_|LargeInteger_|SmallInteger_}] -> {*}
 164[002] - pop, load local S0
 166[026] - load smi 2
 168[020] - load literal  != 
-170[079] - invoke at_put // {*}
+170[079] - invoke at_put // [{LargeArray_|SmallArray_}, {SmallInteger_}, {String_}] -> {*}
 171[002] - pop, load local S0
 173[026] - load smi 3
 175[017] - load local 3
-176[079] - invoke at_put // {*}
+176[079] - invoke at_put // [{LargeArray_|SmallArray_}, {SmallInteger_}, {LargeInteger_|SmallInteger_}] -> {*}
 177[002] - pop, load local S0
 179[026] - load smi 4
 181[020] - load literal 
-183[079] - invoke at_put // {*}
+183[079] - invoke at_put // [{LargeArray_|SmallArray_}, {SmallInteger_}, {String_}] -> {*}
 184[002] - pop, load local S0
 186[004] - store local, pop S1
-188[053] - invoke static simple_interpolate_strings_ <sdk>/core/utils.toit // {String_}
-191[053] - invoke static throw <sdk>/core/exceptions.toit // {}
+188[053] - invoke static simple_interpolate_strings_ <sdk>/core/utils.toit // [{LargeArray_|SmallArray_}] -> {String_}
+191[053] - invoke static throw <sdk>/core/exceptions.toit // [{String_}] -> {}
 194[041] - pop 1
 195[014] - load local 0
 196[014] - load local 0
 197[025] - load smi 1
-198[073] - invoke add // {LargeInteger_|SmallInteger_}
+198[073] - invoke add // [{LargeInteger_|SmallInteger_}, {SmallInteger_}] -> {LargeInteger_|SmallInteger_}
 199[004] - store local, pop S2
 201[041] - pop 1
 202[083] - branch back T117
@@ -1377,54 +1377,54 @@ projection_test tests/type_propagation/deltablue_test.toit
  - argument 0: {SmallInteger_}
   0[052] - load local, as class, pop 2 - LargeInteger_(22 - 24) // {True_}
   2[042] - allocate instance Planner
-  4[053] - invoke static Planner tests/type_propagation/deltablue_test.toit // {Planner}
+  4[053] - invoke static Planner tests/type_propagation/deltablue_test.toit // [{Planner}] -> {Planner}
   7[035] - store global var G7
   9[041] - pop 1
  10[042] - allocate instance Variable
  12[020] - load literal scale
  14[026] - load smi 10
- 16[053] - invoke static Variable tests/type_propagation/deltablue_test.toit // {Variable}
+ 16[053] - invoke static Variable tests/type_propagation/deltablue_test.toit // [{Variable}, {String_}, {SmallInteger_}] -> {Variable}
  19[042] - allocate instance Variable
  21[020] - load literal offset
  23[027] - load smi 1000
- 26[053] - invoke static Variable tests/type_propagation/deltablue_test.toit // {Variable}
+ 26[053] - invoke static Variable tests/type_propagation/deltablue_test.toit // [{Variable}, {String_}, {SmallInteger_}] -> {Variable}
  29[022] - load null
  30[022] - load null
  31[023] - load smi 0
  32[022] - load null
- 33[053] - invoke static Array_ <sdk>/core/collections.toit // {LargeArray_|SmallArray_}
+ 33[053] - invoke static Array_ <sdk>/core/collections.toit // [{SmallInteger_}, {Null_}] -> {LargeArray_|SmallArray_}
  36[014] - load local 0
  37[004] - store local, pop S1
- 39[053] - invoke static create_list_literal_from_array_ <sdk>/core/collections.toit // {List_}
+ 39[053] - invoke static create_list_literal_from_array_ <sdk>/core/collections.toit // [{LargeArray_|SmallArray_}] -> {List_}
  42[023] - load smi 0
  43[014] - load local 0
  44[000] - load local S9
- 46[063] - invoke lt // {True_|False_}
+ 46[063] - invoke lt // [{LargeInteger_|SmallInteger_}, {SmallInteger_}] -> {True_|False_}
  47[082] - branch if false T123
  50[042] - allocate instance Variable
  52[020] - load literal src
  54[016] - load local 2
- 55[058] - invoke virtual stringify // {String_}
- 59[073] - invoke add // {String_}
+ 55[058] - invoke virtual stringify // [{LargeInteger_|SmallInteger_}] -> {String_}
+ 59[073] - invoke add // [{String_}, {String_}] -> {String_}
  60[016] - load local 2
- 61[053] - invoke static Variable tests/type_propagation/deltablue_test.toit // {Variable}
+ 61[053] - invoke static Variable tests/type_propagation/deltablue_test.toit // [{Variable}, {String_}, {LargeInteger_|SmallInteger_}] -> {Variable}
  64[004] - store local, pop S4
  66[042] - allocate instance Variable
  68[020] - load literal dst
  70[016] - load local 2
- 71[058] - invoke virtual stringify // {String_}
- 75[073] - invoke add // {String_}
+ 71[058] - invoke virtual stringify // [{LargeInteger_|SmallInteger_}] -> {String_}
+ 75[073] - invoke add // [{String_}, {String_}] -> {String_}
  76[016] - load local 2
- 77[053] - invoke static Variable tests/type_propagation/deltablue_test.toit // {Variable}
+ 77[053] - invoke static Variable tests/type_propagation/deltablue_test.toit // [{Variable}, {String_}, {LargeInteger_|SmallInteger_}] -> {Variable}
  80[004] - store local, pop S3
  82[015] - load local 1
  83[017] - load local 3
- 84[053] - invoke static List.add <sdk>/core/collections.toit // {Null_}
+ 84[053] - invoke static List.add <sdk>/core/collections.toit // [{List_}, {Variable}] -> {Null_}
  87[041] - pop 1
  88[042] - allocate instance StayConstraint
  90[033] - load global var lazy G4 // {Strength}
  92[019] - load local 5
- 93[053] - invoke static StayConstraint tests/type_propagation/deltablue_test.toit // {StayConstraint}
+ 93[053] - invoke static StayConstraint tests/type_propagation/deltablue_test.toit // [{StayConstraint}, {Strength}, {Variable}] -> {StayConstraint}
  96[041] - pop 1
  97[042] - allocate instance ScaleConstraint
  99[033] - load global var lazy G0 // {Strength}
@@ -1432,98 +1432,98 @@ projection_test tests/type_propagation/deltablue_test.toit
 102[019] - load local 5
 103[000] - load local S9
 105[000] - load local S9
-107[053] - invoke static ScaleConstraint tests/type_propagation/deltablue_test.toit // {ScaleConstraint}
+107[053] - invoke static ScaleConstraint tests/type_propagation/deltablue_test.toit // [{ScaleConstraint}, {Strength}, {Variable}, {Variable}, {Variable}, {Variable}] -> {ScaleConstraint}
 110[041] - pop 1
 111[014] - load local 0
 112[014] - load local 0
 113[025] - load smi 1
-114[073] - invoke add // {LargeInteger_|SmallInteger_}
+114[073] - invoke add // [{LargeInteger_|SmallInteger_}, {SmallInteger_}] -> {LargeInteger_|SmallInteger_}
 115[004] - store local, pop S2
 117[041] - pop 1
 118[083] - branch back T43
 123[002] - pop, load local S2
 125[026] - load smi 17
-127[053] - invoke static change tests/type_propagation/deltablue_test.toit // {Null_}
+127[053] - invoke static change tests/type_propagation/deltablue_test.toit // [{Null_|Variable}, {SmallInteger_}] -> {Null_}
 130[002] - pop, load local S1
-132[060] - invoke virtual get value // {Null_|LargeInteger_|SmallInteger_}
+132[060] - invoke virtual get value // [{Null_|Variable}] -> {Null_|LargeInteger_|SmallInteger_}
 135[027] - load smi 1170
-138[062] - invoke eq // {True_|False_}
+138[062] - invoke eq // [{Null_|LargeInteger_|SmallInteger_}, {SmallInteger_}] -> {True_|False_}
 139[081] - branch if true T148
 142[020] - load literal Projection 1 failed
-144[053] - invoke static throw <sdk>/core/exceptions.toit // {}
+144[053] - invoke static throw <sdk>/core/exceptions.toit // [{String_}] -> {}
 147[041] - pop 1
 148[015] - load local 1
 149[027] - load smi 1050
-152[053] - invoke static change tests/type_propagation/deltablue_test.toit // {Null_}
+152[053] - invoke static change tests/type_propagation/deltablue_test.toit // [{Null_|Variable}, {SmallInteger_}] -> {Null_}
 155[002] - pop, load local S2
-157[060] - invoke virtual get value // {Null_|LargeInteger_|SmallInteger_}
+157[060] - invoke virtual get value // [{Null_|Variable}] -> {Null_|LargeInteger_|SmallInteger_}
 160[026] - load smi 5
-162[062] - invoke eq // {True_|False_}
+162[062] - invoke eq // [{Null_|LargeInteger_|SmallInteger_}, {SmallInteger_}] -> {True_|False_}
 163[081] - branch if true T172
 166[020] - load literal Projection 2 failed
-168[053] - invoke static throw <sdk>/core/exceptions.toit // {}
+168[053] - invoke static throw <sdk>/core/exceptions.toit // [{String_}] -> {}
 171[041] - pop 1
 172[018] - load local 4
 173[026] - load smi 5
-175[053] - invoke static change tests/type_propagation/deltablue_test.toit // {Null_}
+175[053] - invoke static change tests/type_propagation/deltablue_test.toit // [{Variable}, {SmallInteger_}] -> {Null_}
 178[041] - pop 1
 179[023] - load smi 0
 180[014] - load local 0
 181[000] - load local S9
 183[025] - load smi 1
-184[074] - invoke sub // {LargeInteger_|SmallInteger_}
-185[063] - invoke lt // {True_|False_}
+184[074] - invoke sub // [{SmallInteger_}, {SmallInteger_}] -> {LargeInteger_|SmallInteger_}
+185[063] - invoke lt // [{LargeInteger_|SmallInteger_}, {LargeInteger_|SmallInteger_}] -> {True_|False_}
 186[082] - branch if false T225
 189[015] - load local 1
 190[015] - load local 1
-191[078] - invoke at // {*}
-192[060] - invoke virtual get value // {*}
+191[078] - invoke at // [{List_}, {LargeInteger_|SmallInteger_}] -> {*}
+192[060] - invoke virtual get value // [{*}] -> {*}
 195[015] - load local 1
 196[026] - load smi 5
-198[075] - invoke mul // {LargeInteger_|SmallInteger_}
+198[075] - invoke mul // [{LargeInteger_|SmallInteger_}, {SmallInteger_}] -> {LargeInteger_|SmallInteger_}
 199[027] - load smi 1000
-202[073] - invoke add // {LargeInteger_|SmallInteger_}
-203[062] - invoke eq // {True_|False_}
+202[073] - invoke add // [{LargeInteger_|SmallInteger_}, {SmallInteger_}] -> {LargeInteger_|SmallInteger_}
+203[062] - invoke eq // [{*}, {LargeInteger_|SmallInteger_}] -> {True_|False_}
 204[081] - branch if true T213
 207[020] - load literal Projection 3 failed
-209[053] - invoke static throw <sdk>/core/exceptions.toit // {}
+209[053] - invoke static throw <sdk>/core/exceptions.toit // [{String_}] -> {}
 212[041] - pop 1
 213[014] - load local 0
 214[014] - load local 0
 215[025] - load smi 1
-216[073] - invoke add // {LargeInteger_|SmallInteger_}
+216[073] - invoke add // [{LargeInteger_|SmallInteger_}, {SmallInteger_}] -> {LargeInteger_|SmallInteger_}
 217[004] - store local, pop S2
 219[041] - pop 1
 220[083] - branch back T180
 225[002] - pop, load local S3
 227[027] - load smi 2000
-230[053] - invoke static change tests/type_propagation/deltablue_test.toit // {Null_}
+230[053] - invoke static change tests/type_propagation/deltablue_test.toit // [{Variable}, {SmallInteger_}] -> {Null_}
 233[041] - pop 1
 234[023] - load smi 0
 235[014] - load local 0
 236[000] - load local S9
 238[025] - load smi 1
-239[074] - invoke sub // {LargeInteger_|SmallInteger_}
-240[063] - invoke lt // {True_|False_}
+239[074] - invoke sub // [{SmallInteger_}, {SmallInteger_}] -> {LargeInteger_|SmallInteger_}
+240[063] - invoke lt // [{LargeInteger_|SmallInteger_}, {LargeInteger_|SmallInteger_}] -> {True_|False_}
 241[082] - branch if false T280
 244[015] - load local 1
 245[015] - load local 1
-246[078] - invoke at // {*}
-247[060] - invoke virtual get value // {*}
+246[078] - invoke at // [{List_}, {LargeInteger_|SmallInteger_}] -> {*}
+247[060] - invoke virtual get value // [{*}] -> {*}
 250[015] - load local 1
 251[026] - load smi 5
-253[075] - invoke mul // {LargeInteger_|SmallInteger_}
+253[075] - invoke mul // [{LargeInteger_|SmallInteger_}, {SmallInteger_}] -> {LargeInteger_|SmallInteger_}
 254[027] - load smi 2000
-257[073] - invoke add // {LargeInteger_|SmallInteger_}
-258[062] - invoke eq // {True_|False_}
+257[073] - invoke add // [{LargeInteger_|SmallInteger_}, {SmallInteger_}] -> {LargeInteger_|SmallInteger_}
+258[062] - invoke eq // [{*}, {LargeInteger_|SmallInteger_}] -> {True_|False_}
 259[081] - branch if true T268
 262[020] - load literal Projection 4 failed
-264[053] - invoke static throw <sdk>/core/exceptions.toit // {}
+264[053] - invoke static throw <sdk>/core/exceptions.toit // [{String_}] -> {}
 267[041] - pop 1
 268[014] - load local 0
 269[014] - load local 0
 270[025] - load smi 1
-271[073] - invoke add // {LargeInteger_|SmallInteger_}
+271[073] - invoke add // [{LargeInteger_|SmallInteger_}, {SmallInteger_}] -> {LargeInteger_|SmallInteger_}
 272[004] - store local, pop S2
 274[041] - pop 1
 275[083] - branch back T235
@@ -1537,19 +1537,19 @@ change tests/type_propagation/deltablue_test.toit
   4[042] - allocate instance EditConstraint
   6[033] - load global var lazy G2 // {Strength}
   8[019] - load local 5
-  9[053] - invoke static EditConstraint tests/type_propagation/deltablue_test.toit // {EditConstraint}
+  9[053] - invoke static EditConstraint tests/type_propagation/deltablue_test.toit // [{EditConstraint}, {Strength}, {Variable}] -> {EditConstraint}
  12[030] - load global var G7 // {Null_|Planner}
  14[015] - load local 1
- 15[053] - invoke static create_array_ <sdk>/core/collections.toit // {LargeArray_|SmallArray_}
- 18[053] - invoke static create_list_literal_from_array_ <sdk>/core/collections.toit // {List_}
- 21[058] - invoke virtual extract_plan_from_constraints // {Plan}
+ 15[053] - invoke static create_array_ <sdk>/core/collections.toit // [{EditConstraint}] -> {LargeArray_|SmallArray_}
+ 18[053] - invoke static create_list_literal_from_array_ <sdk>/core/collections.toit // [{LargeArray_|SmallArray_}] -> {List_}
+ 21[058] - invoke virtual extract_plan_from_constraints // [{Null_|Planner}, {List_}] -> {Plan}
  25[029] - load [block] in change tests/type_propagation/deltablue_test.toit
  30[026] - load smi 10
  32[038] - load block 1
- 34[058] - invoke virtual repeat // {Null_}
+ 34[058] - invoke virtual repeat // [{SmallInteger_}, [block]] -> {Null_}
  38[041] - pop 1
  39[002] - pop, load local S1
- 41[053] - invoke static Constraint.destroy_constraint tests/type_propagation/deltablue_test.toit // {Null_}
+ 41[053] - invoke static Constraint.destroy_constraint tests/type_propagation/deltablue_test.toit // [{EditConstraint}] -> {Null_}
  44[089] - return null S3 2
 
 [block] in change tests/type_propagation/deltablue_test.toit
@@ -1561,5 +1561,5 @@ change tests/type_propagation/deltablue_test.toit
   6[013] - store field, pop 1
   8[016] - load local 2
   9[005] - load outer S1 // {Plan}
- 11[053] - invoke static Plan.execute tests/type_propagation/deltablue_test.toit // {Null_}
+ 11[053] - invoke static Plan.execute tests/type_propagation/deltablue_test.toit // [{Plan}] -> {Null_}
  14[088] - return S1 1
diff --git a/tests/type_propagation/gold/deltablue_test.gold-O2 b/tests/type_propagation/gold/deltablue_test.gold-O2
index 3af6483ab..0ed77835d 100644
--- a/tests/type_propagation/gold/deltablue_test.gold-O2
+++ b/tests/type_propagation/gold/deltablue_test.gold-O2
@@ -2,16 +2,16 @@ main tests/type_propagation/deltablue_test.toit
   0[029] - load [block] in main tests/type_propagation/deltablue_test.toit
   5[026] - load smi 10
   7[038] - load block 1
-  9[058] - invoke virtual repeat // {Null_}
+  9[058] - invoke virtual repeat // [{SmallInteger_}, [block]] -> {Null_}
  13[089] - return null S2 0
 
 [block] in main tests/type_propagation/deltablue_test.toit
  - argument 0: [block]
   0[026] - load smi 50
-  2[053] - invoke static chain_test tests/type_propagation/deltablue_test.toit // {Null_}
+  2[053] - invoke static chain_test tests/type_propagation/deltablue_test.toit // [{SmallInteger_}] -> {Null_}
   5[041] - pop 1
   6[026] - load smi 50
-  8[053] - invoke static projection_test tests/type_propagation/deltablue_test.toit // {Null_}
+  8[053] - invoke static projection_test tests/type_propagation/deltablue_test.toit // [{SmallInteger_}] -> {Null_}
  11[088] - return S1 1
 
 Strength tests/type_propagation/deltablue_test.toit
@@ -29,44 +29,44 @@ Strength tests/type_propagation/deltablue_test.toit
 
 Strength.value tests/type_propagation/deltablue_test.toit
  - argument 0: {Strength}
-  0[009] - load field local 2 // {Null_|SmallInteger_}
+  0[009] - load field local 2 // [{Strength}] -> {Null_|SmallInteger_}
   2[088] - return S1 1
 
 Strength.next_weaker tests/type_propagation/deltablue_test.toit
  - argument 0: {Strength}
-  0[009] - load field local 2 // {Null_|SmallInteger_}
+  0[009] - load field local 2 // [{Strength}] -> {Null_|SmallInteger_}
   2[023] - load smi 0
-  3[062] - invoke eq // {True_|False_}
+  3[062] - invoke eq // [{Null_|SmallInteger_}, {SmallInteger_}] -> {True_|False_}
   4[082] - branch if false T12
   7[033] - load global var lazy G6 // {Strength}
   9[088] - return S1 1
- 12[009] - load field local 2 // {Null_|SmallInteger_}
+ 12[009] - load field local 2 // [{Strength}] -> {Null_|SmallInteger_}
  14[025] - load smi 1
- 15[062] - invoke eq // {True_|False_}
+ 15[062] - invoke eq // [{Null_|SmallInteger_}, {SmallInteger_}] -> {True_|False_}
  16[082] - branch if false T24
  19[033] - load global var lazy G5 // {Strength}
  21[088] - return S1 1
- 24[009] - load field local 2 // {Null_|SmallInteger_}
+ 24[009] - load field local 2 // [{Strength}] -> {Null_|SmallInteger_}
  26[026] - load smi 2
- 28[062] - invoke eq // {True_|False_}
+ 28[062] - invoke eq // [{Null_|SmallInteger_}, {SmallInteger_}] -> {True_|False_}
  29[082] - branch if false T37
  32[033] - load global var lazy G4 // {Strength}
  34[088] - return S1 1
- 37[009] - load field local 2 // {Null_|SmallInteger_}
+ 37[009] - load field local 2 // [{Strength}] -> {Null_|SmallInteger_}
  39[026] - load smi 3
- 41[062] - invoke eq // {True_|False_}
+ 41[062] - invoke eq // [{Null_|SmallInteger_}, {SmallInteger_}] -> {True_|False_}
  42[082] - branch if false T50
  45[033] - load global var lazy G3 // {Strength}
  47[088] - return S1 1
- 50[009] - load field local 2 // {Null_|SmallInteger_}
+ 50[009] - load field local 2 // [{Strength}] -> {Null_|SmallInteger_}
  52[026] - load smi 4
- 54[062] - invoke eq // {True_|False_}
+ 54[062] - invoke eq // [{Null_|SmallInteger_}, {SmallInteger_}] -> {True_|False_}
  55[082] - branch if false T63
  58[033] - load global var lazy G2 // {Strength}
  60[088] - return S1 1
- 63[009] - load field local 2 // {Null_|SmallInteger_}
+ 63[009] - load field local 2 // [{Strength}] -> {Null_|SmallInteger_}
  65[026] - load smi 5
- 67[062] - invoke eq // {True_|False_}
+ 67[062] - invoke eq // [{Null_|SmallInteger_}, {SmallInteger_}] -> {True_|False_}
  68[082] - branch if false T76
  71[033] - load global var lazy G1 // {Strength}
  73[088] - return S1 1
@@ -77,49 +77,49 @@ REQUIRED tests/type_propagation/deltablue_test.toit
   0[042] - allocate instance Strength
   2[023] - load smi 0
   3[020] - load literal required
-  5[053] - invoke static Strength tests/type_propagation/deltablue_test.toit // {Strength}
+  5[053] - invoke static Strength tests/type_propagation/deltablue_test.toit // [{Strength}, {SmallInteger_}, {String_}] -> {Strength}
   8[088] - return S1 0
 
 STRONG_REFERRED tests/type_propagation/deltablue_test.toit
   0[042] - allocate instance Strength
   2[025] - load smi 1
   3[020] - load literal strongPreferred
-  5[053] - invoke static Strength tests/type_propagation/deltablue_test.toit // {Strength}
+  5[053] - invoke static Strength tests/type_propagation/deltablue_test.toit // [{Strength}, {SmallInteger_}, {String_}] -> {Strength}
   8[088] - return S1 0
 
 PREFERRED tests/type_propagation/deltablue_test.toit
   0[042] - allocate instance Strength
   2[026] - load smi 2
   4[020] - load literal preferred
-  6[053] - invoke static Strength tests/type_propagation/deltablue_test.toit // {Strength}
+  6[053] - invoke static Strength tests/type_propagation/deltablue_test.toit // [{Strength}, {SmallInteger_}, {String_}] -> {Strength}
   9[088] - return S1 0
 
 STRONG_DEFAULT tests/type_propagation/deltablue_test.toit
   0[042] - allocate instance Strength
   2[026] - load smi 3
   4[020] - load literal strongDefault
-  6[053] - invoke static Strength tests/type_propagation/deltablue_test.toit // {Strength}
+  6[053] - invoke static Strength tests/type_propagation/deltablue_test.toit // [{Strength}, {SmallInteger_}, {String_}] -> {Strength}
   9[088] - return S1 0
 
 NORMAL tests/type_propagation/deltablue_test.toit
   0[042] - allocate instance Strength
   2[026] - load smi 4
   4[020] - load literal normal
-  6[053] - invoke static Strength tests/type_propagation/deltablue_test.toit // {Strength}
+  6[053] - invoke static Strength tests/type_propagation/deltablue_test.toit // [{Strength}, {SmallInteger_}, {String_}] -> {Strength}
   9[088] - return S1 0
 
 WEAK_DEFAULT tests/type_propagation/deltablue_test.toit
   0[042] - allocate instance Strength
   2[026] - load smi 5
   4[020] - load literal weakDefault
-  6[053] - invoke static Strength tests/type_propagation/deltablue_test.toit // {Strength}
+  6[053] - invoke static Strength tests/type_propagation/deltablue_test.toit // [{Strength}, {SmallInteger_}, {String_}] -> {Strength}
   9[088] - return S1 0
 
 WEAKEST tests/type_propagation/deltablue_test.toit
   0[042] - allocate instance Strength
   2[026] - load smi 6
   4[020] - load literal weakest
-  6[053] - invoke static Strength tests/type_propagation/deltablue_test.toit // {Strength}
+  6[053] - invoke static Strength tests/type_propagation/deltablue_test.toit // [{Strength}, {SmallInteger_}, {String_}] -> {Strength}
   9[088] - return S1 0
 
 stronger tests/type_propagation/deltablue_test.toit
@@ -127,9 +127,9 @@ stronger tests/type_propagation/deltablue_test.toit
  - argument 1: {Null_|Strength}
   0[052] - load local, as class, pop 3 - Strength(42 - 43) // {True_|False_}
   2[052] - load local, as class, pop 2 - Strength(42 - 43) // {True_|False_}
-  4[009] - load field local 3 // {Null_|SmallInteger_}
-  6[009] - load field local 3 // {Null_|SmallInteger_}
-  8[063] - invoke lt // {True_|False_}
+  4[009] - load field local 3 // [{Strength}] -> {Null_|SmallInteger_}
+  6[009] - load field local 3 // [{Strength}] -> {Null_|SmallInteger_}
+  8[063] - invoke lt // [{Null_|SmallInteger_}, {Null_|SmallInteger_}] -> {True_|False_}
   9[088] - return S1 2
 
 weaker tests/type_propagation/deltablue_test.toit
@@ -137,9 +137,9 @@ weaker tests/type_propagation/deltablue_test.toit
  - argument 1: {Null_|Strength}
   0[052] - load local, as class, pop 3 - Strength(42 - 43) // {True_|False_}
   2[052] - load local, as class, pop 2 - Strength(42 - 43) // {True_|False_}
-  4[009] - load field local 3 // {Null_|SmallInteger_}
-  6[009] - load field local 3 // {Null_|SmallInteger_}
-  8[064] - invoke gt // {True_|False_}
+  4[009] - load field local 3 // [{Strength}] -> {Null_|SmallInteger_}
+  6[009] - load field local 3 // [{Strength}] -> {Null_|SmallInteger_}
+  8[064] - invoke gt // [{Null_|SmallInteger_}, {Null_|SmallInteger_}] -> {True_|False_}
   9[088] - return S1 2
 
 weakest tests/type_propagation/deltablue_test.toit
@@ -149,7 +149,7 @@ weakest tests/type_propagation/deltablue_test.toit
   2[052] - load local, as class, pop 2 - Strength(42 - 43) // {True_|False_}
   4[017] - load local 3
   5[017] - load local 3
-  6[053] - invoke static weaker tests/type_propagation/deltablue_test.toit // {True_|False_}
+  6[053] - invoke static weaker tests/type_propagation/deltablue_test.toit // [{Strength}, {Strength}] -> {True_|False_}
   9[082] - branch if false T19
  12[017] - load local 3
  13[088] - return S1 2
@@ -159,7 +159,7 @@ weakest tests/type_propagation/deltablue_test.toit
 
 Constraint.strength tests/type_propagation/deltablue_test.toit
  - argument 0: {EqualityConstraint|ScaleConstraint|EditConstraint|StayConstraint}
-  0[009] - load field local 2 // {Null_|Strength}
+  0[009] - load field local 2 // [{EqualityConstraint|ScaleConstraint|EditConstraint|StayConstraint}] -> {Null_|Strength}
   2[088] - return S1 1
 
 Constraint tests/type_propagation/deltablue_test.toit
@@ -174,11 +174,11 @@ Constraint tests/type_propagation/deltablue_test.toit
 Constraint.add_constraint tests/type_propagation/deltablue_test.toit
  - argument 0: {EqualityConstraint|ScaleConstraint|EditConstraint|StayConstraint}
   0[016] - load local 2
-  1[058] - invoke virtual add_to_graph // {Null_}
+  1[058] - invoke virtual add_to_graph // [{EqualityConstraint|ScaleConstraint|EditConstraint|StayConstraint}] -> {Null_}
   5[041] - pop 1
   6[030] - load global var G7 // {Null_|Planner}
   8[017] - load local 3
-  9[058] - invoke virtual incremental_add // {Null_}
+  9[058] - invoke virtual incremental_add // [{Null_|Planner}, {EqualityConstraint|ScaleConstraint|EditConstraint|StayConstraint}] -> {Null_}
  13[089] - return null S1 1
 
 Constraint.satisfy tests/type_propagation/deltablue_test.toit
@@ -186,28 +186,28 @@ Constraint.satisfy tests/type_propagation/deltablue_test.toit
  - argument 1: {LargeInteger_|SmallInteger_}
   0[017] - load local 3
   1[017] - load local 3
-  2[058] - invoke virtual choose_method // {Null_}
+  2[058] - invoke virtual choose_method // [{EqualityConstraint|ScaleConstraint|EditConstraint|StayConstraint}, {LargeInteger_|SmallInteger_}] -> {Null_}
   6[002] - pop, load local S3
-  8[060] - invoke virtual get is_satisfied // {Null_|True_|False_}
+  8[060] - invoke virtual get is_satisfied // [{EqualityConstraint|ScaleConstraint|EditConstraint|StayConstraint}] -> {Null_|True_|False_}
  11[081] - branch if true T31
- 14[009] - load field local 3 // {Null_|Strength}
+ 14[009] - load field local 3 // [{EqualityConstraint|ScaleConstraint|EditConstraint|StayConstraint}] -> {Null_|Strength}
  16[033] - load global var lazy G0 // {Strength}
- 18[062] - invoke eq // {True_|False_}
+ 18[062] - invoke eq // [{Null_|Strength}, {Strength}] -> {True_|False_}
  19[082] - branch if false T28
  22[020] - load literal Could not satisfy a required constraint!
- 24[053] - invoke static throw <sdk>/core/exceptions.toit // {}
+ 24[053] - invoke static throw <sdk>/core/exceptions.toit // [{String_}] -> {}
  27[041] - pop 1
  28[089] - return null S0 2
  31[017] - load local 3
  32[017] - load local 3
- 33[058] - invoke virtual mark_inputs // {Null_}
+ 33[058] - invoke virtual mark_inputs // [{EqualityConstraint|ScaleConstraint|EditConstraint|StayConstraint}, {LargeInteger_|SmallInteger_}] -> {Null_}
  37[002] - pop, load local S3
- 39[058] - invoke virtual output // {Null_|Variable}
- 43[009] - load field local 32 // {Null_|EqualityConstraint|ScaleConstraint|EditConstraint|StayConstraint}
+ 39[058] - invoke virtual output // [{EqualityConstraint|ScaleConstraint|EditConstraint|StayConstraint}] -> {Null_|Variable}
+ 43[009] - load field local 32 // [{Null_|Variable}] -> {Null_|EqualityConstraint|ScaleConstraint|EditConstraint|StayConstraint}
  45[014] - load local 0
  46[082] - branch if false T55
  49[014] - load local 0
- 50[058] - invoke virtual mark_unsatisfied // {Null_}
+ 50[058] - invoke virtual mark_unsatisfied // [{Null_|EqualityConstraint|ScaleConstraint|EditConstraint|StayConstraint}] -> {Null_}
  54[041] - pop 1
  55[015] - load local 1
  56[000] - load local S6
@@ -215,10 +215,10 @@ Constraint.satisfy tests/type_propagation/deltablue_test.toit
  60[030] - load global var G7 // {Null_|Planner}
  62[000] - load local S6
  64[000] - load local S6
- 66[058] - invoke virtual add_propagate // {True_|False_}
+ 66[058] - invoke virtual add_propagate // [{Null_|Planner}, {EqualityConstraint|ScaleConstraint|EditConstraint|StayConstraint}, {LargeInteger_|SmallInteger_}] -> {True_|False_}
  70[081] - branch if true T79
  73[020] - load literal Cycle encountered
- 75[053] - invoke static throw <sdk>/core/exceptions.toit // {}
+ 75[053] - invoke static throw <sdk>/core/exceptions.toit // [{String_}] -> {}
  78[041] - pop 1
  79[015] - load local 1
  80[019] - load local 5
@@ -229,14 +229,14 @@ Constraint.satisfy tests/type_propagation/deltablue_test.toit
 Constraint.destroy_constraint tests/type_propagation/deltablue_test.toit
  - argument 0: {EditConstraint}
   0[016] - load local 2
-  1[060] - invoke virtual get is_satisfied // {Null_|True_|False_}
+  1[060] - invoke virtual get is_satisfied // [{EditConstraint}] -> {Null_|True_|False_}
   4[082] - branch if false T15
   7[030] - load global var G7 // {Null_|Planner}
   9[017] - load local 3
- 10[058] - invoke virtual incremental_remove // {Null_}
+ 10[058] - invoke virtual incremental_remove // [{Null_|Planner}, {EditConstraint}] -> {Null_}
  14[041] - pop 1
  15[016] - load local 2
- 16[058] - invoke virtual remove_from_graph // {Null_}
+ 16[058] - invoke virtual remove_from_graph // [{EditConstraint}] -> {Null_}
  20[089] - return null S1 1
 
 Constraint.is_input tests/type_propagation/deltablue_test.toit
@@ -246,7 +246,7 @@ Constraint.is_input tests/type_propagation/deltablue_test.toit
 
 UnaryConstraint.is_satisfied tests/type_propagation/deltablue_test.toit
  - argument 0: {EditConstraint|StayConstraint}
-  0[009] - load field local 34 // {Null_|True_|False_}
+  0[009] - load field local 34 // [{EditConstraint|StayConstraint}] -> {Null_|True_|False_}
   2[088] - return S1 1
 
 UnaryConstraint tests/type_propagation/deltablue_test.toit
@@ -261,17 +261,17 @@ UnaryConstraint tests/type_propagation/deltablue_test.toit
   7[013] - store field, pop 2
   9[018] - load local 4
  10[018] - load local 4
- 11[053] - invoke static Constraint tests/type_propagation/deltablue_test.toit // {EditConstraint|StayConstraint}
+ 11[053] - invoke static Constraint tests/type_propagation/deltablue_test.toit // [{EditConstraint|StayConstraint}, {Strength}] -> {EditConstraint|StayConstraint}
  14[002] - pop, load local S4
- 16[053] - invoke static Constraint.add_constraint tests/type_propagation/deltablue_test.toit // {Null_}
+ 16[053] - invoke static Constraint.add_constraint tests/type_propagation/deltablue_test.toit // [{EditConstraint|StayConstraint}] -> {Null_}
  19[002] - pop, load local S4
  21[088] - return S1 3
 
 UnaryConstraint.add_to_graph tests/type_propagation/deltablue_test.toit
  - argument 0: {EditConstraint|StayConstraint}
-  0[009] - load field local 18 // {Null_|Variable}
+  0[009] - load field local 18 // [{EditConstraint|StayConstraint}] -> {Null_|Variable}
   2[017] - load local 3
-  3[053] - invoke static Variable.add_constraint tests/type_propagation/deltablue_test.toit // {Null_}
+  3[053] - invoke static Variable.add_constraint tests/type_propagation/deltablue_test.toit // [{Null_|Variable}, {EditConstraint|StayConstraint}] -> {Null_}
   6[002] - pop, load local S2
   8[020] - load literal false
  10[013] - store field, pop 2
@@ -281,20 +281,20 @@ UnaryConstraint.choose_method tests/type_propagation/deltablue_test.toit
  - argument 0: {EditConstraint|StayConstraint}
  - argument 1: {LargeInteger_|SmallInteger_}
   0[017] - load local 3
-  1[009] - load field local 20 // {Null_|Variable}
-  3[007] - load field 3 // {Null_|LargeInteger_|SmallInteger_}
+  1[009] - load field local 20 // [{EditConstraint|StayConstraint}] -> {Null_|Variable}
+  3[007] - load field 3 // [{Null_|Variable}] -> {Null_|LargeInteger_|SmallInteger_}
   5[018] - load local 4
-  6[062] - invoke eq // {True_|False_}
+  6[062] - invoke eq // [{Null_|LargeInteger_|SmallInteger_}, {LargeInteger_|SmallInteger_}] -> {True_|False_}
   7[081] - branch if true T15
  10[020] - load literal true
  12[080] - branch T17
  15[020] - load literal false
  17[014] - load local 0
  18[082] - branch if false T30
- 21[010] - pop, load field local 4 // {Null_|Strength}
- 23[009] - load field local 21 // {Null_|Variable}
- 25[007] - load field 4 // {Null_|Strength}
- 27[053] - invoke static stronger tests/type_propagation/deltablue_test.toit // {True_|False_}
+ 21[010] - pop, load field local 4 // [{EditConstraint|StayConstraint}] -> {Null_|Strength}
+ 23[009] - load field local 21 // [{EditConstraint|StayConstraint}] -> {Null_|Variable}
+ 25[007] - load field 4 // [{Null_|Variable}] -> {Null_|Strength}
+ 27[053] - invoke static stronger tests/type_propagation/deltablue_test.toit // [{Null_|Strength}, {Null_|Strength}] -> {True_|False_}
  30[013] - store field, pop 2
  32[089] - return null S0 2
 
@@ -305,27 +305,27 @@ UnaryConstraint.mark_inputs tests/type_propagation/deltablue_test.toit
 
 UnaryConstraint.output tests/type_propagation/deltablue_test.toit
  - argument 0: {EditConstraint|StayConstraint}
-  0[009] - load field local 18 // {Null_|Variable}
+  0[009] - load field local 18 // [{EditConstraint|StayConstraint}] -> {Null_|Variable}
   2[088] - return S1 1
 
 UnaryConstraint.recalculate tests/type_propagation/deltablue_test.toit
  - argument 0: {EditConstraint|StayConstraint}
-  0[009] - load field local 18 // {Null_|Variable}
-  2[009] - load field local 3 // {Null_|Strength}
+  0[009] - load field local 18 // [{EditConstraint|StayConstraint}] -> {Null_|Variable}
+  2[009] - load field local 3 // [{EditConstraint|StayConstraint}] -> {Null_|Strength}
   4[013] - store field, pop 4
-  6[009] - load field local 18 // {Null_|Variable}
+  6[009] - load field local 18 // [{EditConstraint|StayConstraint}] -> {Null_|Variable}
   8[017] - load local 3
-  9[058] - invoke virtual is_input // {True_|False_}
+  9[058] - invoke virtual is_input // [{EditConstraint|StayConstraint}] -> {True_|False_}
  13[081] - branch if true T21
  16[020] - load literal true
  18[080] - branch T23
  21[020] - load literal false
  23[013] - store field, pop 5
- 25[009] - load field local 18 // {Null_|Variable}
- 27[007] - load field 5 // {Null_|True_|False_}
+ 25[009] - load field local 18 // [{EditConstraint|StayConstraint}] -> {Null_|Variable}
+ 27[007] - load field 5 // [{Null_|Variable}] -> {Null_|True_|False_}
  29[082] - branch if false T38
  32[016] - load local 2
- 33[058] - invoke virtual execute // {Null_}
+ 33[058] - invoke virtual execute // [{EditConstraint|StayConstraint}] -> {Null_}
  37[041] - pop 1
  38[089] - return null S0 1
 
@@ -344,9 +344,9 @@ UnaryConstraint.inputs_known tests/type_propagation/deltablue_test.toit
 
 UnaryConstraint.remove_from_graph tests/type_propagation/deltablue_test.toit
  - argument 0: {EditConstraint|StayConstraint}
-  0[009] - load field local 18 // {Null_|Variable}
+  0[009] - load field local 18 // [{EditConstraint|StayConstraint}] -> {Null_|Variable}
   2[017] - load local 3
-  3[053] - invoke static Variable.remove_constraint tests/type_propagation/deltablue_test.toit // {Null_}
+  3[053] - invoke static Variable.remove_constraint tests/type_propagation/deltablue_test.toit // [{Null_|Variable}, {EditConstraint|StayConstraint}] -> {Null_}
   6[002] - pop, load local S2
   8[020] - load literal false
  10[013] - store field, pop 2
@@ -360,7 +360,7 @@ StayConstraint tests/type_propagation/deltablue_test.toit
   2[018] - load local 4
   3[018] - load local 4
   4[018] - load local 4
-  5[053] - invoke static UnaryConstraint tests/type_propagation/deltablue_test.toit // {StayConstraint}
+  5[053] - invoke static UnaryConstraint tests/type_propagation/deltablue_test.toit // [{StayConstraint}, {Strength}, {Variable}] -> {StayConstraint}
   8[002] - pop, load local S4
  10[088] - return S1 3
 
@@ -376,7 +376,7 @@ EditConstraint tests/type_propagation/deltablue_test.toit
   2[018] - load local 4
   3[018] - load local 4
   4[018] - load local 4
-  5[053] - invoke static UnaryConstraint tests/type_propagation/deltablue_test.toit // {EditConstraint}
+  5[053] - invoke static UnaryConstraint tests/type_propagation/deltablue_test.toit // [{EditConstraint}, {Strength}, {Variable}] -> {EditConstraint}
   8[002] - pop, load local S4
  10[088] - return S1 3
 
@@ -405,69 +405,69 @@ BinaryConstraint tests/type_propagation/deltablue_test.toit
  10[013] - store field, pop 3
  12[019] - load local 5
  13[019] - load local 5
- 14[053] - invoke static Constraint tests/type_propagation/deltablue_test.toit // {EqualityConstraint|ScaleConstraint}
+ 14[053] - invoke static Constraint tests/type_propagation/deltablue_test.toit // [{EqualityConstraint|ScaleConstraint}, {Strength}] -> {EqualityConstraint|ScaleConstraint}
  17[002] - pop, load local S5
- 19[053] - invoke static Constraint.add_constraint tests/type_propagation/deltablue_test.toit // {Null_}
+ 19[053] - invoke static Constraint.add_constraint tests/type_propagation/deltablue_test.toit // [{EqualityConstraint|ScaleConstraint}] -> {Null_}
  22[002] - pop, load local S5
  24[088] - return S1 4
 
 BinaryConstraint.choose_method tests/type_propagation/deltablue_test.toit
  - argument 0: {EqualityConstraint|ScaleConstraint}
  - argument 1: {LargeInteger_|SmallInteger_}
-  0[009] - load field local 19 // {Null_|Variable}
-  2[007] - load field 3 // {Null_|LargeInteger_|SmallInteger_}
+  0[009] - load field local 19 // [{EqualityConstraint|ScaleConstraint}] -> {Null_|Variable}
+  2[007] - load field 3 // [{Null_|Variable}] -> {Null_|LargeInteger_|SmallInteger_}
   4[017] - load local 3
-  5[062] - invoke eq // {True_|False_}
+  5[062] - invoke eq // [{Null_|LargeInteger_|SmallInteger_}, {LargeInteger_|SmallInteger_}] -> {True_|False_}
   6[082] - branch if false T40
   9[017] - load local 3
  10[025] - load smi 1
- 11[009] - load field local 37 // {Null_|Variable}
- 13[007] - load field 3 // {Null_|LargeInteger_|SmallInteger_}
+ 11[009] - load field local 37 // [{EqualityConstraint|ScaleConstraint}] -> {Null_|Variable}
+ 13[007] - load field 3 // [{Null_|Variable}] -> {Null_|LargeInteger_|SmallInteger_}
  15[019] - load local 5
- 16[062] - invoke eq // {True_|False_}
+ 16[062] - invoke eq // [{Null_|LargeInteger_|SmallInteger_}, {LargeInteger_|SmallInteger_}] -> {True_|False_}
  17[081] - branch if true T35
- 20[009] - load field local 5 // {Null_|Strength}
- 22[009] - load field local 38 // {Null_|Variable}
- 24[007] - load field 4 // {Null_|Strength}
- 26[053] - invoke static stronger tests/type_propagation/deltablue_test.toit // {True_|False_}
+ 20[009] - load field local 5 // [{EqualityConstraint|ScaleConstraint}] -> {Null_|Strength}
+ 22[009] - load field local 38 // [{EqualityConstraint|ScaleConstraint}] -> {Null_|Variable}
+ 24[007] - load field 4 // [{Null_|Variable}] -> {Null_|Strength}
+ 26[053] - invoke static stronger tests/type_propagation/deltablue_test.toit // [{Null_|Strength}, {Null_|Strength}] -> {True_|False_}
  29[082] - branch if false T35
  32[041] - pop 1
  33[026] - load smi 2
  35[013] - store field, pop 3
  37[080] - branch T133
- 40[009] - load field local 35 // {Null_|Variable}
- 42[007] - load field 3 // {Null_|LargeInteger_|SmallInteger_}
+ 40[009] - load field local 35 // [{EqualityConstraint|ScaleConstraint}] -> {Null_|Variable}
+ 42[007] - load field 3 // [{Null_|Variable}] -> {Null_|LargeInteger_|SmallInteger_}
  44[017] - load local 3
- 45[062] - invoke eq // {True_|False_}
+ 45[062] - invoke eq // [{Null_|LargeInteger_|SmallInteger_}, {LargeInteger_|SmallInteger_}] -> {True_|False_}
  46[082] - branch if false T79
  49[017] - load local 3
  50[025] - load smi 1
- 51[009] - load field local 21 // {Null_|Variable}
- 53[007] - load field 3 // {Null_|LargeInteger_|SmallInteger_}
+ 51[009] - load field local 21 // [{EqualityConstraint|ScaleConstraint}] -> {Null_|Variable}
+ 53[007] - load field 3 // [{Null_|Variable}] -> {Null_|LargeInteger_|SmallInteger_}
  55[019] - load local 5
- 56[062] - invoke eq // {True_|False_}
+ 56[062] - invoke eq // [{Null_|LargeInteger_|SmallInteger_}, {LargeInteger_|SmallInteger_}] -> {True_|False_}
  57[081] - branch if true T74
- 60[009] - load field local 5 // {Null_|Strength}
- 62[009] - load field local 22 // {Null_|Variable}
- 64[007] - load field 4 // {Null_|Strength}
- 66[053] - invoke static stronger tests/type_propagation/deltablue_test.toit // {True_|False_}
+ 60[009] - load field local 5 // [{EqualityConstraint|ScaleConstraint}] -> {Null_|Strength}
+ 62[009] - load field local 22 // [{EqualityConstraint|ScaleConstraint}] -> {Null_|Variable}
+ 64[007] - load field 4 // [{Null_|Variable}] -> {Null_|Strength}
+ 66[053] - invoke static stronger tests/type_propagation/deltablue_test.toit // [{Null_|Strength}, {Null_|Strength}] -> {True_|False_}
  69[082] - branch if false T74
  72[041] - pop 1
  73[023] - load smi 0
  74[013] - store field, pop 3
  76[080] - branch T133
- 79[009] - load field local 19 // {Null_|Variable}
- 81[007] - load field 4 // {Null_|Strength}
- 83[009] - load field local 36 // {Null_|Variable}
- 85[007] - load field 4 // {Null_|Strength}
- 87[053] - invoke static weaker tests/type_propagation/deltablue_test.toit // {True_|False_}
+ 79[009] - load field local 19 // [{EqualityConstraint|ScaleConstraint}] -> {Null_|Variable}
+ 81[007] - load field 4 // [{Null_|Variable}] -> {Null_|Strength}
+ 83[009] - load field local 36 // [{EqualityConstraint|ScaleConstraint}] -> {Null_|Variable}
+ 85[007] - load field 4 // [{Null_|Variable}] -> {Null_|Strength}
+ 87[053] - invoke static weaker tests/type_propagation/deltablue_test.toit // [{Null_|Strength}, {Null_|Strength}] -> {True_|False_}
  90[082] - branch if false T114
  93[017] - load local 3
  94[025] - load smi 1
- 95[009] - load field local 5 // {Null_|Strength}
- 97[009] - load field local 22 // {Null_|Variable}
- 99[007] - load field 4 // {Null_|Strength}
-101[053] - invoke static stronger tests/type_propagation/deltablue_test.toit // {True_|False_}
+ 95[009] - load field local 5 // [{EqualityConstraint|ScaleConstraint}] -> {Null_|Strength}
+ 97[009] - load field local 22 // [{EqualityConstraint|ScaleConstraint}] -> {Null_|Variable}
+ 99[007] - load field 4 // [{Null_|Variable}] -> {Null_|Strength}
+101[053] - invoke static stronger tests/type_propagation/deltablue_test.toit // [{Null_|Strength}, {Null_|Strength}] -> {True_|False_}
 104[082] - branch if false T109
 107[041] - pop 1
 108[023] - load smi 0
@@ -475,10 +475,10 @@ BinaryConstraint.choose_method tests/type_propagation/deltablue_test.toit
 111[080] - branch T133
 114[017] - load local 3
 115[023] - load smi 0
-116[009] - load field local 5 // {Null_|Strength}
-118[009] - load field local 38 // {Null_|Variable}
-120[007] - load field 4 // {Null_|Strength}
-122[053] - invoke static stronger tests/type_propagation/deltablue_test.toit // {True_|False_}
+116[009] - load field local 5 // [{EqualityConstraint|ScaleConstraint}] -> {Null_|Strength}
+118[009] - load field local 38 // [{EqualityConstraint|ScaleConstraint}] -> {Null_|Variable}
+120[007] - load field 4 // [{Null_|Variable}] -> {Null_|Strength}
+122[053] - invoke static stronger tests/type_propagation/deltablue_test.toit // [{Null_|Strength}, {Null_|Strength}] -> {True_|False_}
 125[082] - branch if false T131
 128[041] - pop 1
 129[026] - load smi 2
@@ -487,12 +487,12 @@ BinaryConstraint.choose_method tests/type_propagation/deltablue_test.toit
 
 BinaryConstraint.add_to_graph tests/type_propagation/deltablue_test.toit
  - argument 0: {EqualityConstraint|ScaleConstraint}
-  0[009] - load field local 18 // {Null_|Variable}
+  0[009] - load field local 18 // [{EqualityConstraint|ScaleConstraint}] -> {Null_|Variable}
   2[017] - load local 3
-  3[053] - invoke static Variable.add_constraint tests/type_propagation/deltablue_test.toit // {Null_}
-  6[010] - pop, load field local 34 // {Null_|Variable}
+  3[053] - invoke static Variable.add_constraint tests/type_propagation/deltablue_test.toit // [{Null_|Variable}, {EqualityConstraint|ScaleConstraint}] -> {Null_}
+  6[010] - pop, load field local 34 // [{EqualityConstraint|ScaleConstraint}] -> {Null_|Variable}
   8[017] - load local 3
-  9[053] - invoke static Variable.add_constraint tests/type_propagation/deltablue_test.toit // {Null_}
+  9[053] - invoke static Variable.add_constraint tests/type_propagation/deltablue_test.toit // [{Null_|Variable}, {EqualityConstraint|ScaleConstraint}] -> {Null_}
  12[002] - pop, load local S2
  14[025] - load smi 1
  15[013] - store field, pop 3
@@ -500,9 +500,9 @@ BinaryConstraint.add_to_graph tests/type_propagation/deltablue_test.toit
 
 BinaryConstraint.is_satisfied tests/type_propagation/deltablue_test.toit
  - argument 0: {EqualityConstraint|ScaleConstraint}
-  0[009] - load field local 50 // {Null_|SmallInteger_}
+  0[009] - load field local 50 // [{EqualityConstraint|ScaleConstraint}] -> {Null_|SmallInteger_}
   2[025] - load smi 1
-  3[062] - invoke eq // {True_|False_}
+  3[062] - invoke eq // [{Null_|SmallInteger_}, {SmallInteger_}] -> {True_|False_}
   4[081] - branch if true T12
   7[020] - load literal true
   9[080] - branch T14
@@ -513,53 +513,53 @@ BinaryConstraint.mark_inputs tests/type_propagation/deltablue_test.toit
  - argument 0: {EqualityConstraint|ScaleConstraint}
  - argument 1: {LargeInteger_|SmallInteger_}
   0[017] - load local 3
-  1[053] - invoke static BinaryConstraint.input tests/type_propagation/deltablue_test.toit // {Variable}
+  1[053] - invoke static BinaryConstraint.input tests/type_propagation/deltablue_test.toit // [{EqualityConstraint|ScaleConstraint}] -> {Variable}
   4[017] - load local 3
   5[013] - store field, pop 3
   7[089] - return null S0 2
 
 BinaryConstraint.input tests/type_propagation/deltablue_test.toit
  - argument 0: {EqualityConstraint|ScaleConstraint}
-  0[009] - load field local 50 // {Null_|SmallInteger_}
+  0[009] - load field local 50 // [{EqualityConstraint|ScaleConstraint}] -> {Null_|SmallInteger_}
   2[026] - load smi 2
-  4[062] - invoke eq // {True_|False_}
+  4[062] - invoke eq // [{Null_|SmallInteger_}, {SmallInteger_}] -> {True_|False_}
   5[082] - branch if false T13
-  8[009] - load field local 18 // {Null_|Variable}
+  8[009] - load field local 18 // [{EqualityConstraint|ScaleConstraint}] -> {Null_|Variable}
  10[080] - branch T15
- 13[009] - load field local 34 // {Null_|Variable}
+ 13[009] - load field local 34 // [{EqualityConstraint|ScaleConstraint}] -> {Null_|Variable}
  15[048] - as class Variable(37 - 38) // {True_|False_}
  17[088] - return S1 1
 
 BinaryConstraint.output tests/type_propagation/deltablue_test.toit
  - argument 0: {EqualityConstraint|ScaleConstraint}
-  0[009] - load field local 50 // {Null_|SmallInteger_}
+  0[009] - load field local 50 // [{EqualityConstraint|ScaleConstraint}] -> {Null_|SmallInteger_}
   2[026] - load smi 2
-  4[062] - invoke eq // {True_|False_}
+  4[062] - invoke eq // [{Null_|SmallInteger_}, {SmallInteger_}] -> {True_|False_}
   5[082] - branch if false T13
-  8[009] - load field local 34 // {Null_|Variable}
+  8[009] - load field local 34 // [{EqualityConstraint|ScaleConstraint}] -> {Null_|Variable}
  10[080] - branch T15
- 13[009] - load field local 18 // {Null_|Variable}
+ 13[009] - load field local 18 // [{EqualityConstraint|ScaleConstraint}] -> {Null_|Variable}
  15[048] - as class Variable(37 - 38) // {True_|False_}
  17[088] - return S1 1
 
 BinaryConstraint.recalculate tests/type_propagation/deltablue_test.toit
  - argument 0: {EqualityConstraint}
   0[016] - load local 2
-  1[053] - invoke static BinaryConstraint.input tests/type_propagation/deltablue_test.toit // {Variable}
+  1[053] - invoke static BinaryConstraint.input tests/type_propagation/deltablue_test.toit // [{EqualityConstraint}] -> {Variable}
   4[017] - load local 3
-  5[053] - invoke static BinaryConstraint.output tests/type_propagation/deltablue_test.toit // {Variable}
+  5[053] - invoke static BinaryConstraint.output tests/type_propagation/deltablue_test.toit // [{EqualityConstraint}] -> {Variable}
   8[014] - load local 0
-  9[009] - load field local 5 // {Null_|Strength}
- 11[009] - load field local 67 // {Null_|Strength}
- 13[053] - invoke static weakest tests/type_propagation/deltablue_test.toit // {Strength}
+  9[009] - load field local 5 // [{EqualityConstraint}] -> {Null_|Strength}
+ 11[009] - load field local 67 // [{Variable}] -> {Null_|Strength}
+ 13[053] - invoke static weakest tests/type_propagation/deltablue_test.toit // [{Null_|Strength}, {Null_|Strength}] -> {Strength}
  16[013] - store field, pop 4
  18[014] - load local 0
- 19[009] - load field local 82 // {Null_|True_|False_}
+ 19[009] - load field local 82 // [{Variable}] -> {Null_|True_|False_}
  21[013] - store field, pop 5
- 23[009] - load field local 80 // {Null_|True_|False_}
+ 23[009] - load field local 80 // [{Variable}] -> {Null_|True_|False_}
  25[082] - branch if false T34
  28[018] - load local 4
- 29[058] - invoke virtual execute // {Null_}
+ 29[058] - invoke virtual execute // [{EqualityConstraint}] -> {Null_}
  33[041] - pop 1
  34[089] - return null S2 1
 
@@ -574,27 +574,27 @@ BinaryConstraint.inputs_known tests/type_propagation/deltablue_test.toit
  - argument 0: {EqualityConstraint|ScaleConstraint}
  - argument 1: {LargeInteger_|SmallInteger_}
   0[017] - load local 3
-  1[053] - invoke static BinaryConstraint.input tests/type_propagation/deltablue_test.toit // {Variable}
-  4[009] - load field local 48 // {Null_|LargeInteger_|SmallInteger_}
+  1[053] - invoke static BinaryConstraint.input tests/type_propagation/deltablue_test.toit // [{EqualityConstraint|ScaleConstraint}] -> {Variable}
+  4[009] - load field local 48 // [{Variable}] -> {Null_|LargeInteger_|SmallInteger_}
   6[018] - load local 4
-  7[062] - invoke eq // {True_|False_}
+  7[062] - invoke eq // [{Null_|LargeInteger_|SmallInteger_}, {LargeInteger_|SmallInteger_}] -> {True_|False_}
   8[014] - load local 0
   9[081] - branch if true T20
- 12[010] - pop, load field local 80 // {Null_|True_|False_}
+ 12[010] - pop, load field local 80 // [{Variable}] -> {Null_|True_|False_}
  14[014] - load local 0
  15[081] - branch if true T20
- 18[010] - pop, load field local 32 // {Null_|EqualityConstraint|ScaleConstraint|EditConstraint|StayConstraint}
+ 18[010] - pop, load field local 32 // [{Variable}] -> {Null_|EqualityConstraint|ScaleConstraint|EditConstraint|StayConstraint}
  20[048] - as class True_(15 - 17) // {True_|False_}
  22[088] - return S2 2
 
 BinaryConstraint.remove_from_graph tests/type_propagation/deltablue_test.toit
  - argument 0: {EqualityConstraint|ScaleConstraint}
-  0[009] - load field local 18 // {Null_|Variable}
+  0[009] - load field local 18 // [{EqualityConstraint|ScaleConstraint}] -> {Null_|Variable}
   2[017] - load local 3
-  3[053] - invoke static Variable.remove_constraint tests/type_propagation/deltablue_test.toit // {Null_}
-  6[010] - pop, load field local 34 // {Null_|Variable}
+  3[053] - invoke static Variable.remove_constraint tests/type_propagation/deltablue_test.toit // [{Null_|Variable}, {EqualityConstraint|ScaleConstraint}] -> {Null_}
+  6[010] - pop, load field local 34 // [{EqualityConstraint|ScaleConstraint}] -> {Null_|Variable}
   8[017] - load local 3
-  9[053] - invoke static Variable.remove_constraint tests/type_propagation/deltablue_test.toit // {Null_}
+  9[053] - invoke static Variable.remove_constraint tests/type_propagation/deltablue_test.toit // [{Null_|Variable}, {EqualityConstraint|ScaleConstraint}] -> {Null_}
  12[002] - pop, load local S2
  14[025] - load smi 1
  15[013] - store field, pop 3
@@ -617,32 +617,32 @@ ScaleConstraint tests/type_propagation/deltablue_test.toit
  12[000] - load local S7
  14[000] - load local S7
  16[000] - load local S7
- 18[053] - invoke static BinaryConstraint tests/type_propagation/deltablue_test.toit // {ScaleConstraint}
+ 18[053] - invoke static BinaryConstraint tests/type_propagation/deltablue_test.toit // [{ScaleConstraint}, {Strength}, {Variable}, {Variable}] -> {ScaleConstraint}
  21[002] - pop, load local S7
  23[088] - return S1 6
 
 ScaleConstraint.add_to_graph tests/type_propagation/deltablue_test.toit
  - argument 0: {ScaleConstraint}
   0[016] - load local 2
-  1[053] - invoke static BinaryConstraint.add_to_graph tests/type_propagation/deltablue_test.toit // {Null_}
-  4[010] - pop, load field local 66 // {Null_|Variable}
+  1[053] - invoke static BinaryConstraint.add_to_graph tests/type_propagation/deltablue_test.toit // [{ScaleConstraint}] -> {Null_}
+  4[010] - pop, load field local 66 // [{ScaleConstraint}] -> {Null_|Variable}
   6[017] - load local 3
-  7[053] - invoke static Variable.add_constraint tests/type_propagation/deltablue_test.toit // {Null_}
- 10[010] - pop, load field local 82 // {Null_|Variable}
+  7[053] - invoke static Variable.add_constraint tests/type_propagation/deltablue_test.toit // [{Null_|Variable}, {ScaleConstraint}] -> {Null_}
+ 10[010] - pop, load field local 82 // [{ScaleConstraint}] -> {Null_|Variable}
  12[017] - load local 3
- 13[053] - invoke static Variable.add_constraint tests/type_propagation/deltablue_test.toit // {Null_}
+ 13[053] - invoke static Variable.add_constraint tests/type_propagation/deltablue_test.toit // [{Null_|Variable}, {ScaleConstraint}] -> {Null_}
  16[089] - return null S1 1
 
 ScaleConstraint.remove_from_graph tests/type_propagation/deltablue_test.toit
  - argument 0: {ScaleConstraint}
   0[016] - load local 2
-  1[053] - invoke static BinaryConstraint.remove_from_graph tests/type_propagation/deltablue_test.toit // {Null_}
-  4[010] - pop, load field local 66 // {Null_|Variable}
+  1[053] - invoke static BinaryConstraint.remove_from_graph tests/type_propagation/deltablue_test.toit // [{ScaleConstraint}] -> {Null_}
+  4[010] - pop, load field local 66 // [{ScaleConstraint}] -> {Null_|Variable}
   6[017] - load local 3
-  7[053] - invoke static Variable.remove_constraint tests/type_propagation/deltablue_test.toit // {Null_}
- 10[010] - pop, load field local 82 // {Null_|Variable}
+  7[053] - invoke static Variable.remove_constraint tests/type_propagation/deltablue_test.toit // [{Null_|Variable}, {ScaleConstraint}] -> {Null_}
+ 10[010] - pop, load field local 82 // [{ScaleConstraint}] -> {Null_|Variable}
  12[017] - load local 3
- 13[053] - invoke static Variable.remove_constraint tests/type_propagation/deltablue_test.toit // {Null_}
+ 13[053] - invoke static Variable.remove_constraint tests/type_propagation/deltablue_test.toit // [{Null_|Variable}, {ScaleConstraint}] -> {Null_}
  16[089] - return null S1 1
 
 ScaleConstraint.mark_inputs tests/type_propagation/deltablue_test.toit
@@ -650,9 +650,9 @@ ScaleConstraint.mark_inputs tests/type_propagation/deltablue_test.toit
  - argument 1: {LargeInteger_|SmallInteger_}
   0[017] - load local 3
   1[017] - load local 3
-  2[053] - invoke static BinaryConstraint.mark_inputs tests/type_propagation/deltablue_test.toit // {Null_}
-  5[010] - pop, load field local 67 // {Null_|Variable}
-  7[009] - load field local 84 // {Null_|Variable}
+  2[053] - invoke static BinaryConstraint.mark_inputs tests/type_propagation/deltablue_test.toit // [{ScaleConstraint}, {LargeInteger_|SmallInteger_}] -> {Null_}
+  5[010] - pop, load field local 67 // [{ScaleConstraint}] -> {Null_|Variable}
+  7[009] - load field local 84 // [{ScaleConstraint}] -> {Null_|Variable}
   9[018] - load local 4
  10[011] - store field 3
  12[013] - store field, pop 3
@@ -660,59 +660,59 @@ ScaleConstraint.mark_inputs tests/type_propagation/deltablue_test.toit
 
 ScaleConstraint.execute tests/type_propagation/deltablue_test.toit
  - argument 0: {ScaleConstraint}
-  0[009] - load field local 50 // {Null_|SmallInteger_}
+  0[009] - load field local 50 // [{ScaleConstraint}] -> {Null_|SmallInteger_}
   2[026] - load smi 2
-  4[062] - invoke eq // {True_|False_}
+  4[062] - invoke eq // [{Null_|SmallInteger_}, {SmallInteger_}] -> {True_|False_}
   5[082] - branch if false T29
-  8[009] - load field local 34 // {Null_|Variable}
- 10[009] - load field local 19 // {Null_|Variable}
- 12[007] - load field 1 // {Null_|LargeInteger_|SmallInteger_}
- 14[009] - load field local 68 // {Null_|Variable}
- 16[007] - load field 1 // {Null_|LargeInteger_|SmallInteger_}
- 18[075] - invoke mul // {LargeInteger_|SmallInteger_}
- 19[009] - load field local 84 // {Null_|Variable}
- 21[007] - load field 1 // {Null_|LargeInteger_|SmallInteger_}
- 23[073] - invoke add // {LargeInteger_|SmallInteger_}
+  8[009] - load field local 34 // [{ScaleConstraint}] -> {Null_|Variable}
+ 10[009] - load field local 19 // [{ScaleConstraint}] -> {Null_|Variable}
+ 12[007] - load field 1 // [{Null_|Variable}] -> {Null_|LargeInteger_|SmallInteger_}
+ 14[009] - load field local 68 // [{ScaleConstraint}] -> {Null_|Variable}
+ 16[007] - load field 1 // [{Null_|Variable}] -> {Null_|LargeInteger_|SmallInteger_}
+ 18[075] - invoke mul // [{Null_|LargeInteger_|SmallInteger_}, {Null_|LargeInteger_|SmallInteger_}] -> {LargeInteger_|SmallInteger_}
+ 19[009] - load field local 84 // [{ScaleConstraint}] -> {Null_|Variable}
+ 21[007] - load field 1 // [{Null_|Variable}] -> {Null_|LargeInteger_|SmallInteger_}
+ 23[073] - invoke add // [{LargeInteger_|SmallInteger_}, {Null_|LargeInteger_|SmallInteger_}] -> {LargeInteger_|SmallInteger_}
  24[013] - store field, pop 1
  26[080] - branch T47
- 29[009] - load field local 18 // {Null_|Variable}
- 31[009] - load field local 35 // {Null_|Variable}
- 33[007] - load field 1 // {Null_|LargeInteger_|SmallInteger_}
- 35[009] - load field local 84 // {Null_|Variable}
- 37[007] - load field 1 // {Null_|LargeInteger_|SmallInteger_}
- 39[074] - invoke sub // {LargeInteger_|SmallInteger_}
- 40[009] - load field local 68 // {Null_|Variable}
- 42[007] - load field 1 // {Null_|LargeInteger_|SmallInteger_}
- 44[076] - invoke div // {LargeInteger_|SmallInteger_}
+ 29[009] - load field local 18 // [{ScaleConstraint}] -> {Null_|Variable}
+ 31[009] - load field local 35 // [{ScaleConstraint}] -> {Null_|Variable}
+ 33[007] - load field 1 // [{Null_|Variable}] -> {Null_|LargeInteger_|SmallInteger_}
+ 35[009] - load field local 84 // [{ScaleConstraint}] -> {Null_|Variable}
+ 37[007] - load field 1 // [{Null_|Variable}] -> {Null_|LargeInteger_|SmallInteger_}
+ 39[074] - invoke sub // [{Null_|LargeInteger_|SmallInteger_}, {Null_|LargeInteger_|SmallInteger_}] -> {LargeInteger_|SmallInteger_}
+ 40[009] - load field local 68 // [{ScaleConstraint}] -> {Null_|Variable}
+ 42[007] - load field 1 // [{Null_|Variable}] -> {Null_|LargeInteger_|SmallInteger_}
+ 44[076] - invoke div // [{LargeInteger_|SmallInteger_}, {Null_|LargeInteger_|SmallInteger_}] -> {LargeInteger_|SmallInteger_}
  45[013] - store field, pop 1
  47[089] - return null S0 1
 
 ScaleConstraint.recalculate tests/type_propagation/deltablue_test.toit
  - argument 0: {ScaleConstraint}
   0[016] - load local 2
-  1[053] - invoke static BinaryConstraint.input tests/type_propagation/deltablue_test.toit // {Variable}
+  1[053] - invoke static BinaryConstraint.input tests/type_propagation/deltablue_test.toit // [{ScaleConstraint}] -> {Variable}
   4[017] - load local 3
-  5[053] - invoke static BinaryConstraint.output tests/type_propagation/deltablue_test.toit // {Variable}
+  5[053] - invoke static BinaryConstraint.output tests/type_propagation/deltablue_test.toit // [{ScaleConstraint}] -> {Variable}
   8[014] - load local 0
-  9[009] - load field local 5 // {Null_|Strength}
- 11[009] - load field local 67 // {Null_|Strength}
- 13[053] - invoke static weakest tests/type_propagation/deltablue_test.toit // {Strength}
+  9[009] - load field local 5 // [{ScaleConstraint}] -> {Null_|Strength}
+ 11[009] - load field local 67 // [{Variable}] -> {Null_|Strength}
+ 13[053] - invoke static weakest tests/type_propagation/deltablue_test.toit // [{Null_|Strength}, {Null_|Strength}] -> {Strength}
  16[013] - store field, pop 4
  18[014] - load local 0
- 19[009] - load field local 82 // {Null_|True_|False_}
+ 19[009] - load field local 82 // [{Variable}] -> {Null_|True_|False_}
  21[014] - load local 0
  22[082] - branch if false T37
- 25[010] - pop, load field local 69 // {Null_|Variable}
- 27[007] - load field 5 // {Null_|True_|False_}
+ 25[010] - pop, load field local 69 // [{ScaleConstraint}] -> {Null_|Variable}
+ 27[007] - load field 5 // [{Null_|Variable}] -> {Null_|True_|False_}
  29[014] - load local 0
  30[082] - branch if false T37
- 33[010] - pop, load field local 85 // {Null_|Variable}
- 35[007] - load field 5 // {Null_|True_|False_}
+ 33[010] - pop, load field local 85 // [{ScaleConstraint}] -> {Null_|Variable}
+ 35[007] - load field 5 // [{Null_|Variable}] -> {Null_|True_|False_}
  37[013] - store field, pop 5
- 39[009] - load field local 80 // {Null_|True_|False_}
+ 39[009] - load field local 80 // [{Variable}] -> {Null_|True_|False_}
  41[082] - branch if false T49
  44[018] - load local 4
- 45[053] - invoke static ScaleConstraint.execute tests/type_propagation/deltablue_test.toit // {Null_}
+ 45[053] - invoke static ScaleConstraint.execute tests/type_propagation/deltablue_test.toit // [{ScaleConstraint}] -> {Null_}
  48[041] - pop 1
  49[089] - return null S2 1
 
@@ -726,17 +726,17 @@ EqualityConstraint tests/type_propagation/deltablue_test.toit
   3[019] - load local 5
   4[019] - load local 5
   5[019] - load local 5
-  6[053] - invoke static BinaryConstraint tests/type_propagation/deltablue_test.toit // {EqualityConstraint}
+  6[053] - invoke static BinaryConstraint tests/type_propagation/deltablue_test.toit // [{EqualityConstraint}, {Strength}, {Variable}, {Variable}] -> {EqualityConstraint}
   9[002] - pop, load local S5
  11[088] - return S1 4
 
 EqualityConstraint.execute tests/type_propagation/deltablue_test.toit
  - argument 0: {EqualityConstraint}
   0[016] - load local 2
-  1[053] - invoke static BinaryConstraint.output tests/type_propagation/deltablue_test.toit // {Variable}
+  1[053] - invoke static BinaryConstraint.output tests/type_propagation/deltablue_test.toit // [{EqualityConstraint}] -> {Variable}
   4[017] - load local 3
-  5[053] - invoke static BinaryConstraint.input tests/type_propagation/deltablue_test.toit // {Variable}
-  8[007] - load field 1 // {Null_|LargeInteger_|SmallInteger_}
+  5[053] - invoke static BinaryConstraint.input tests/type_propagation/deltablue_test.toit // [{EqualityConstraint}] -> {Variable}
+  8[007] - load field 1 // [{Variable}] -> {Null_|LargeInteger_|SmallInteger_}
  10[013] - store field, pop 1
  12[089] - return null S0 1
 
@@ -762,17 +762,17 @@ Variable tests/type_propagation/deltablue_test.toit
  22[018] - load local 4
  23[023] - load smi 0
  24[022] - load null
- 25[053] - invoke static Array_ <sdk>/core/collections.toit // {LargeArray_|SmallArray_}
+ 25[053] - invoke static Array_ <sdk>/core/collections.toit // [{SmallInteger_}, {Null_}] -> {LargeArray_|SmallArray_}
  28[014] - load local 0
  29[004] - store local, pop S1
- 31[053] - invoke static create_list_literal_from_array_ <sdk>/core/collections.toit // {List_}
+ 31[053] - invoke static create_list_literal_from_array_ <sdk>/core/collections.toit // [{LargeArray_|SmallArray_}] -> {List_}
  34[013] - store field, pop 6
  36[018] - load local 4
  37[088] - return S1 3
 
 Variable.value tests/type_propagation/deltablue_test.toit
  - argument 0: {Variable}
-  0[009] - load field local 18 // {Null_|LargeInteger_|SmallInteger_}
+  0[009] - load field local 18 // [{Variable}] -> {Null_|LargeInteger_|SmallInteger_}
   2[088] - return S1 1
 
 Variable.value= tests/type_propagation/deltablue_test.toit
@@ -785,12 +785,12 @@ Variable.value= tests/type_propagation/deltablue_test.toit
 
 Variable.determined_by tests/type_propagation/deltablue_test.toit
  - argument 0: {Variable}
-  0[009] - load field local 34 // {Null_|EqualityConstraint|ScaleConstraint|EditConstraint|StayConstraint}
+  0[009] - load field local 34 // [{Variable}] -> {Null_|EqualityConstraint|ScaleConstraint|EditConstraint|StayConstraint}
   2[088] - return S1 1
 
 Variable.mark tests/type_propagation/deltablue_test.toit
  - argument 0: {Variable}
-  0[009] - load field local 50 // {Null_|LargeInteger_|SmallInteger_}
+  0[009] - load field local 50 // [{Variable}] -> {Null_|LargeInteger_|SmallInteger_}
   2[088] - return S1 1
 
 Variable.mark= tests/type_propagation/deltablue_test.toit
@@ -803,30 +803,30 @@ Variable.mark= tests/type_propagation/deltablue_test.toit
 
 Variable.constraints tests/type_propagation/deltablue_test.toit
  - argument 0: {Variable}
-  0[009] - load field local 98 // {Null_|List_}
+  0[009] - load field local 98 // [{Variable}] -> {Null_|List_}
   2[088] - return S1 1
 
 Variable.add_constraint tests/type_propagation/deltablue_test.toit
  - argument 0: {Variable}
  - argument 1: {EqualityConstraint|ScaleConstraint|EditConstraint|StayConstraint}
-  0[009] - load field local 99 // {Null_|List_}
+  0[009] - load field local 99 // [{Variable}] -> {Null_|List_}
   2[017] - load local 3
-  3[058] - invoke virtual add // {Null_}
+  3[058] - invoke virtual add // [{Null_|List_}, {EqualityConstraint|ScaleConstraint|EditConstraint|StayConstraint}] -> {Null_}
   7[089] - return null S1 2
 
 Variable.remove_constraint tests/type_propagation/deltablue_test.toit
  - argument 0: {Variable}
  - argument 1: {EqualityConstraint|ScaleConstraint|EditConstraint|StayConstraint}
-  0[009] - load field local 99 // {Null_|List_}
+  0[009] - load field local 99 // [{Variable}] -> {Null_|List_}
   2[029] - load [block] in Variable.remove_constraint tests/type_propagation/deltablue_test.toit
   7[015] - load local 1
   8[038] - load block 1
  10[020] - load literal true
- 12[058] - invoke virtual filter // {List_}
+ 12[058] - invoke virtual filter // [{Null_|List_}, [block], {True_}] -> {List_}
  16[040] - pop 3
- 18[009] - load field local 35 // {Null_|EqualityConstraint|ScaleConstraint|EditConstraint|StayConstraint}
+ 18[009] - load field local 35 // [{Variable}] -> {Null_|EqualityConstraint|ScaleConstraint|EditConstraint|StayConstraint}
  20[017] - load local 3
- 21[062] - invoke eq // {True_|False_}
+ 21[062] - invoke eq // [{Null_|EqualityConstraint|ScaleConstraint|EditConstraint|StayConstraint}, {EqualityConstraint|ScaleConstraint|EditConstraint|StayConstraint}] -> {True_|False_}
  22[082] - branch if false T29
  25[017] - load local 3
  26[022] - load null
@@ -839,7 +839,7 @@ Variable.remove_constraint tests/type_propagation/deltablue_test.toit
   0[016] - load local 2
   1[018] - load local 4
   2[005] - load outer S4 // {EqualityConstraint|ScaleConstraint|EditConstraint|StayConstraint}
-  4[062] - invoke eq // {True_|False_}
+  4[062] - invoke eq // [{*}, {EqualityConstraint|ScaleConstraint|EditConstraint|StayConstraint}] -> {True_|False_}
   5[081] - branch if true T13
   8[020] - load literal true
  10[080] - branch T15
@@ -859,15 +859,15 @@ Planner.incremental_add tests/type_propagation/deltablue_test.toit
  - argument 1: {*}
   0[052] - load local, as class, pop 2 - EqualityConstraint(38 - 42) // {True_|False_}
   2[017] - load local 3
-  3[053] - invoke static Planner.new_mark tests/type_propagation/deltablue_test.toit // {LargeInteger_|SmallInteger_}
+  3[053] - invoke static Planner.new_mark tests/type_propagation/deltablue_test.toit // [{Planner}] -> {LargeInteger_|SmallInteger_}
   6[017] - load local 3
   7[015] - load local 1
-  8[053] - invoke static Constraint.satisfy tests/type_propagation/deltablue_test.toit // {Null_|EqualityConstraint|ScaleConstraint|EditConstraint|StayConstraint}
+  8[053] - invoke static Constraint.satisfy tests/type_propagation/deltablue_test.toit // [{EqualityConstraint|ScaleConstraint|EditConstraint|StayConstraint}, {LargeInteger_|SmallInteger_}] -> {Null_|EqualityConstraint|ScaleConstraint|EditConstraint|StayConstraint}
  11[014] - load local 0
  12[082] - branch if false T28
  15[014] - load local 0
  16[016] - load local 2
- 17[058] - invoke virtual satisfy // {Null_|EqualityConstraint|ScaleConstraint|EditConstraint|StayConstraint}
+ 17[058] - invoke virtual satisfy // [{Null_|EqualityConstraint|ScaleConstraint|EditConstraint|StayConstraint}, {LargeInteger_|SmallInteger_}] -> {Null_|EqualityConstraint|ScaleConstraint|EditConstraint|StayConstraint}
  21[004] - store local, pop S1
  23[083] - branch back T11
  28[089] - return null S2 2
@@ -876,26 +876,26 @@ Planner.incremental_remove tests/type_propagation/deltablue_test.toit
  - argument 0: {Planner}
  - argument 1: {EqualityConstraint|ScaleConstraint|EditConstraint|StayConstraint}
   0[016] - load local 2
-  1[058] - invoke virtual output // {Null_|Variable}
+  1[058] - invoke virtual output // [{EqualityConstraint|ScaleConstraint|EditConstraint|StayConstraint}] -> {Null_|Variable}
   5[017] - load local 3
-  6[058] - invoke virtual mark_unsatisfied // {Null_}
+  6[058] - invoke virtual mark_unsatisfied // [{EqualityConstraint|ScaleConstraint|EditConstraint|StayConstraint}] -> {Null_}
  10[002] - pop, load local S3
- 12[058] - invoke virtual remove_from_graph // {Null_}
+ 12[058] - invoke virtual remove_from_graph // [{EqualityConstraint|ScaleConstraint|EditConstraint|StayConstraint}] -> {Null_}
  16[002] - pop, load local S4
  18[015] - load local 1
- 19[053] - invoke static Planner.remove_propagate_from tests/type_propagation/deltablue_test.toit // {List_}
+ 19[053] - invoke static Planner.remove_propagate_from tests/type_propagation/deltablue_test.toit // [{Planner}, {Null_|Variable}] -> {List_}
  22[033] - load global var lazy G0 // {Strength}
  24[029] - load [block] in Planner.incremental_remove tests/type_propagation/deltablue_test.toit
  29[016] - load local 2
  30[038] - load block 1
- 32[058] - invoke virtual do // {Null_}
+ 32[058] - invoke virtual do // [{List_}, [block]] -> {Null_}
  36[041] - pop 1
  37[002] - pop, load local S0
- 39[058] - invoke virtual next_weaker // {Strength}
+ 39[058] - invoke virtual next_weaker // [{Strength}] -> {Strength}
  43[004] - store local, pop S1
  45[014] - load local 0
  46[033] - load global var lazy G6 // {Strength}
- 48[062] - invoke eq // {True_|False_}
+ 48[062] - invoke eq // [{Strength}, {Strength}] -> {True_|False_}
  49[082] - branch if false T55
  52[080] - branch T60
  55[083] - branch back T24
@@ -906,23 +906,23 @@ Planner.incremental_remove tests/type_propagation/deltablue_test.toit
  - argument 1: {*}
   0[022] - load null
   1[017] - load local 3
-  2[060] - invoke virtual get strength // {Null_|Strength}
+  2[060] - invoke virtual get strength // [{*}] -> {Null_|Strength}
   5[019] - load local 5
   6[005] - load outer S1 // {Strength}
-  8[062] - invoke eq // {True_|False_}
+  8[062] - invoke eq // [{Null_|Strength}, {Strength}] -> {True_|False_}
   9[082] - branch if false T20
  12[002] - pop, load local S3
  14[005] - load outer S7 // {Planner}
  16[017] - load local 3
- 17[053] - invoke static Planner.incremental_add tests/type_propagation/deltablue_test.toit // {Null_}
+ 17[053] - invoke static Planner.incremental_add tests/type_propagation/deltablue_test.toit // [{Planner}, {*}] -> {Null_}
  20[088] - return S1 2
 
 Planner.new_mark tests/type_propagation/deltablue_test.toit
  - argument 0: {Planner}
   0[016] - load local 2
-  1[009] - load field local 3 // {Null_|LargeInteger_|SmallInteger_}
+  1[009] - load field local 3 // [{Planner}] -> {Null_|LargeInteger_|SmallInteger_}
   3[025] - load smi 1
-  4[073] - invoke add // {LargeInteger_|SmallInteger_}
+  4[073] - invoke add // [{Null_|LargeInteger_|SmallInteger_}, {SmallInteger_}] -> {LargeInteger_|SmallInteger_}
   5[011] - store field 0
   7[088] - return S1 1
 
@@ -930,37 +930,37 @@ Planner.make_plan tests/type_propagation/deltablue_test.toit
  - argument 0: {Planner}
  - argument 1: {List_}
   0[017] - load local 3
-  1[053] - invoke static Planner.new_mark tests/type_propagation/deltablue_test.toit // {LargeInteger_|SmallInteger_}
+  1[053] - invoke static Planner.new_mark tests/type_propagation/deltablue_test.toit // [{Planner}] -> {LargeInteger_|SmallInteger_}
   4[042] - allocate instance Plan
-  6[053] - invoke static Plan tests/type_propagation/deltablue_test.toit // {Plan}
+  6[053] - invoke static Plan tests/type_propagation/deltablue_test.toit // [{Plan}] -> {Plan}
   9[018] - load local 4
  10[014] - load local 0
- 11[053] - invoke static CollectionBase.is_empty <sdk>/core/collections.toit // {True_|False_}
+ 11[053] - invoke static CollectionBase.is_empty <sdk>/core/collections.toit // [{List_}] -> {True_|False_}
  14[081] - branch if true T77
  17[014] - load local 0
- 18[058] - invoke virtual remove_last // {*}
+ 18[058] - invoke virtual remove_last // [{List_}] -> {*}
  22[014] - load local 0
- 23[058] - invoke virtual output // {Null_|Variable}
- 27[060] - invoke virtual get mark // {Null_|LargeInteger_|SmallInteger_}
+ 23[058] - invoke virtual output // [{*}] -> {Null_|Variable}
+ 27[060] - invoke virtual get mark // [{Null_|Variable}] -> {Null_|LargeInteger_|SmallInteger_}
  30[018] - load local 4
- 31[062] - invoke eq // {True_|False_}
+ 31[062] - invoke eq // [{Null_|LargeInteger_|SmallInteger_}, {LargeInteger_|SmallInteger_}] -> {True_|False_}
  32[081] - branch if true T71
  35[014] - load local 0
  36[018] - load local 4
- 37[058] - invoke virtual inputs_known // {True_|False_}
+ 37[058] - invoke virtual inputs_known // [{*}, {LargeInteger_|SmallInteger_}] -> {True_|False_}
  41[082] - branch if false T71
  44[016] - load local 2
  45[015] - load local 1
- 46[053] - invoke static Plan.add_constraint tests/type_propagation/deltablue_test.toit // {Null_}
+ 46[053] - invoke static Plan.add_constraint tests/type_propagation/deltablue_test.toit // [{Plan}, {*}] -> {Null_}
  49[002] - pop, load local S0
- 51[058] - invoke virtual output // {Null_|Variable}
+ 51[058] - invoke virtual output // [{*}] -> {Null_|Variable}
  55[018] - load local 4
- 56[061] - invoke virtual set mark // {LargeInteger_|SmallInteger_}
+ 56[061] - invoke virtual set mark // [{Null_|Variable}, {LargeInteger_|SmallInteger_}] -> {LargeInteger_|SmallInteger_}
  59[002] - pop, load local S7
  61[015] - load local 1
- 62[058] - invoke virtual output // {Null_|Variable}
+ 62[058] - invoke virtual output // [{*}] -> {Null_|Variable}
  66[017] - load local 3
- 67[053] - invoke static Planner.add_constraints_consuming_to tests/type_propagation/deltablue_test.toit // {Null_}
+ 67[053] - invoke static Planner.add_constraints_consuming_to tests/type_propagation/deltablue_test.toit // [{Planner}, {Null_|Variable}, {List_}] -> {Null_}
  70[041] - pop 1
  71[041] - pop 1
  72[083] - branch back T10
@@ -972,18 +972,18 @@ Planner.extract_plan_from_constraints tests/type_propagation/deltablue_test.toit
  - argument 1: {List_}
   0[023] - load smi 0
   1[022] - load null
-  2[053] - invoke static Array_ <sdk>/core/collections.toit // {LargeArray_|SmallArray_}
+  2[053] - invoke static Array_ <sdk>/core/collections.toit // [{SmallInteger_}, {Null_}] -> {LargeArray_|SmallArray_}
   5[014] - load local 0
   6[004] - store local, pop S1
-  8[053] - invoke static create_list_literal_from_array_ <sdk>/core/collections.toit // {List_}
+  8[053] - invoke static create_list_literal_from_array_ <sdk>/core/collections.toit // [{LargeArray_|SmallArray_}] -> {List_}
  11[029] - load [block] in Planner.extract_plan_from_constraints tests/type_propagation/deltablue_test.toit
  16[018] - load local 4
  17[038] - load block 1
- 19[058] - invoke virtual do // {Null_}
+ 19[058] - invoke virtual do // [{List_}, [block]] -> {Null_}
  23[041] - pop 1
  24[002] - pop, load local S4
  26[015] - load local 1
- 27[053] - invoke static Planner.make_plan tests/type_propagation/deltablue_test.toit // {Plan}
+ 27[053] - invoke static Planner.make_plan tests/type_propagation/deltablue_test.toit // [{Planner}, {List_}] -> {Plan}
  30[088] - return S2 2
 
 [block] in Planner.extract_plan_from_constraints tests/type_propagation/deltablue_test.toit
@@ -991,15 +991,15 @@ Planner.extract_plan_from_constraints tests/type_propagation/deltablue_test.toit
  - argument 1: {*}
   0[022] - load null
   1[017] - load local 3
-  2[058] - invoke virtual is_input // {True_|False_}
+  2[058] - invoke virtual is_input // [{*}] -> {True_|False_}
   6[082] - branch if false T24
   9[017] - load local 3
- 10[060] - invoke virtual get is_satisfied // {Null_|True_|False_}
+ 10[060] - invoke virtual get is_satisfied // [{*}] -> {Null_|True_|False_}
  13[082] - branch if false T24
  16[002] - pop, load local S3
  18[005] - load outer S1 // {List_}
  20[017] - load local 3
- 21[053] - invoke static List.add <sdk>/core/collections.toit // {Null_}
+ 21[053] - invoke static List.add <sdk>/core/collections.toit // [{List_}, {*}] -> {Null_}
  24[088] - return S1 2
 
 Planner.add_propagate tests/type_propagation/deltablue_test.toit
@@ -1007,32 +1007,32 @@ Planner.add_propagate tests/type_propagation/deltablue_test.toit
  - argument 1: {EqualityConstraint|ScaleConstraint|EditConstraint|StayConstraint}
  - argument 2: {LargeInteger_|SmallInteger_}
   0[017] - load local 3
-  1[053] - invoke static create_array_ <sdk>/core/collections.toit // {LargeArray_|SmallArray_}
-  4[053] - invoke static create_list_literal_from_array_ <sdk>/core/collections.toit // {List_}
+  1[053] - invoke static create_array_ <sdk>/core/collections.toit // [{EqualityConstraint|ScaleConstraint|EditConstraint|StayConstraint}] -> {LargeArray_|SmallArray_}
+  4[053] - invoke static create_list_literal_from_array_ <sdk>/core/collections.toit // [{LargeArray_|SmallArray_}] -> {List_}
   7[014] - load local 0
-  8[053] - invoke static CollectionBase.is_empty <sdk>/core/collections.toit // {True_|False_}
+  8[053] - invoke static CollectionBase.is_empty <sdk>/core/collections.toit // [{List_}] -> {True_|False_}
  11[081] - branch if true T68
  14[014] - load local 0
- 15[058] - invoke virtual remove_last // {*}
+ 15[058] - invoke virtual remove_last // [{List_}] -> {*}
  19[014] - load local 0
- 20[058] - invoke virtual output // {Null_|Variable}
- 24[060] - invoke virtual get mark // {Null_|LargeInteger_|SmallInteger_}
+ 20[058] - invoke virtual output // [{*}] -> {Null_|Variable}
+ 24[060] - invoke virtual get mark // [{Null_|Variable}] -> {Null_|LargeInteger_|SmallInteger_}
  27[019] - load local 5
- 28[062] - invoke eq // {True_|False_}
+ 28[062] - invoke eq // [{Null_|LargeInteger_|SmallInteger_}, {LargeInteger_|SmallInteger_}] -> {True_|False_}
  29[082] - branch if false T45
  32[000] - load local S6
  34[000] - load local S6
- 36[053] - invoke static Planner.incremental_remove tests/type_propagation/deltablue_test.toit // {Null_}
+ 36[053] - invoke static Planner.incremental_remove tests/type_propagation/deltablue_test.toit // [{Planner}, {EqualityConstraint|ScaleConstraint|EditConstraint|StayConstraint}] -> {Null_}
  39[041] - pop 1
  40[020] - load literal false
  42[088] - return S3 3
  45[014] - load local 0
- 46[058] - invoke virtual recalculate // {Null_}
+ 46[058] - invoke virtual recalculate // [{*}] -> {Null_}
  50[002] - pop, load local S6
  52[015] - load local 1
- 53[058] - invoke virtual output // {Null_|Variable}
+ 53[058] - invoke virtual output // [{*}] -> {Null_|Variable}
  57[017] - load local 3
- 58[053] - invoke static Planner.add_constraints_consuming_to tests/type_propagation/deltablue_test.toit // {Null_}
+ 58[053] - invoke static Planner.add_constraints_consuming_to tests/type_propagation/deltablue_test.toit // [{Planner}, {Null_|Variable}, {List_}] -> {Null_}
  61[040] - pop 2
  63[083] - branch back T7
  68[020] - load literal true
@@ -1053,31 +1053,31 @@ Planner.remove_propagate_from tests/type_propagation/deltablue_test.toit
  14[013] - store field, pop 5
  16[023] - load smi 0
  17[022] - load null
- 18[053] - invoke static Array_ <sdk>/core/collections.toit // {LargeArray_|SmallArray_}
+ 18[053] - invoke static Array_ <sdk>/core/collections.toit // [{SmallInteger_}, {Null_}] -> {LargeArray_|SmallArray_}
  21[014] - load local 0
  22[004] - store local, pop S1
- 24[053] - invoke static create_list_literal_from_array_ <sdk>/core/collections.toit // {List_}
+ 24[053] - invoke static create_list_literal_from_array_ <sdk>/core/collections.toit // [{LargeArray_|SmallArray_}] -> {List_}
  27[017] - load local 3
- 28[053] - invoke static create_array_ <sdk>/core/collections.toit // {LargeArray_|SmallArray_}
- 31[053] - invoke static create_list_literal_from_array_ <sdk>/core/collections.toit // {List_}
+ 28[053] - invoke static create_array_ <sdk>/core/collections.toit // [{Variable}] -> {LargeArray_|SmallArray_}
+ 31[053] - invoke static create_list_literal_from_array_ <sdk>/core/collections.toit // [{LargeArray_|SmallArray_}] -> {List_}
  34[014] - load local 0
- 35[053] - invoke static CollectionBase.is_empty <sdk>/core/collections.toit // {True_|False_}
+ 35[053] - invoke static CollectionBase.is_empty <sdk>/core/collections.toit // [{List_}] -> {True_|False_}
  38[081] - branch if true T89
  41[014] - load local 0
- 42[058] - invoke virtual remove_last // {*}
+ 42[058] - invoke virtual remove_last // [{List_}] -> {*}
  46[029] - load [block] in Planner.remove_propagate_from tests/type_propagation/deltablue_test.toit
  51[015] - load local 1
- 52[060] - invoke virtual get constraints // {Null_|List_}
+ 52[060] - invoke virtual get constraints // [{*}] -> {Null_|List_}
  55[038] - load block 1
- 57[058] - invoke virtual do // {Null_}
+ 57[058] - invoke virtual do // [{Null_|List_}, [block]] -> {Null_}
  61[041] - pop 1
  62[002] - pop, load local S0
- 64[060] - invoke virtual get determined_by // {Null_|EqualityConstraint|ScaleConstraint|EditConstraint|StayConstraint}
+ 64[060] - invoke virtual get determined_by // [{*}] -> {Null_|EqualityConstraint|ScaleConstraint|EditConstraint|StayConstraint}
  67[029] - load [block] in Planner.remove_propagate_from tests/type_propagation/deltablue_test.toit
  72[016] - load local 2
- 73[060] - invoke virtual get constraints // {Null_|List_}
+ 73[060] - invoke virtual get constraints // [{*}] -> {Null_|List_}
  76[038] - load block 1
- 78[058] - invoke virtual do // {Null_}
+ 78[058] - invoke virtual do // [{Null_|List_}, [block]] -> {Null_}
  82[040] - pop 4
  84[083] - branch back T34
  89[015] - load local 1
@@ -1088,12 +1088,12 @@ Planner.remove_propagate_from tests/type_propagation/deltablue_test.toit
  - argument 1: {*}
   0[022] - load null
   1[017] - load local 3
-  2[060] - invoke virtual get is_satisfied // {Null_|True_|False_}
+  2[060] - invoke virtual get is_satisfied // [{*}] -> {Null_|True_|False_}
   5[081] - branch if true T16
   8[002] - pop, load local S3
  10[005] - load outer S3 // {List_}
  12[017] - load local 3
- 13[053] - invoke static List.add <sdk>/core/collections.toit // {Null_}
+ 13[053] - invoke static List.add <sdk>/core/collections.toit // [{List_}, {*}] -> {Null_}
  16[088] - return S1 2
 
 [block] in Planner.remove_propagate_from tests/type_propagation/deltablue_test.toit
@@ -1103,18 +1103,18 @@ Planner.remove_propagate_from tests/type_propagation/deltablue_test.toit
   1[017] - load local 3
   2[019] - load local 5
   3[005] - load outer S1 // {Null_|EqualityConstraint|ScaleConstraint|EditConstraint|StayConstraint}
-  5[062] - invoke eq // {True_|False_}
+  5[062] - invoke eq // [{*}, {Null_|EqualityConstraint|ScaleConstraint|EditConstraint|StayConstraint}] -> {True_|False_}
   6[081] - branch if true T34
   9[017] - load local 3
- 10[060] - invoke virtual get is_satisfied // {Null_|True_|False_}
+ 10[060] - invoke virtual get is_satisfied // [{*}] -> {Null_|True_|False_}
  13[082] - branch if false T34
  16[002] - pop, load local S2
- 18[058] - invoke virtual recalculate // {Null_}
+ 18[058] - invoke virtual recalculate // [{*}] -> {Null_}
  22[002] - pop, load local S3
  24[005] - load outer S3 // {List_}
  26[017] - load local 3
- 27[058] - invoke virtual output // {Null_|Variable}
- 31[053] - invoke static List.add <sdk>/core/collections.toit // {Null_}
+ 27[058] - invoke virtual output // [{*}] -> {Null_|Variable}
+ 31[053] - invoke static List.add <sdk>/core/collections.toit // [{List_}, {Null_|Variable}] -> {Null_}
  34[088] - return S1 2
 
 Planner.add_constraints_consuming_to tests/type_propagation/deltablue_test.toit
@@ -1122,11 +1122,11 @@ Planner.add_constraints_consuming_to tests/type_propagation/deltablue_test.toit
  - argument 1: {Null_|Variable}
  - argument 2: {List_}
   0[052] - load local, as class, pop 3 - Variable(37 - 38) // {True_|False_}
-  2[009] - load field local 35 // {Null_|EqualityConstraint|ScaleConstraint|EditConstraint|StayConstraint}
+  2[009] - load field local 35 // [{Variable}] -> {Null_|EqualityConstraint|ScaleConstraint|EditConstraint|StayConstraint}
   4[029] - load [block] in Planner.add_constraints_consuming_to tests/type_propagation/deltablue_test.toit
-  9[009] - load field local 101 // {Null_|List_}
+  9[009] - load field local 101 // [{Variable}] -> {Null_|List_}
  11[038] - load block 1
- 13[058] - invoke virtual do // {Null_}
+ 13[058] - invoke virtual do // [{Null_|List_}, [block]] -> {Null_}
  17[089] - return null S3 3
 
 [block] in Planner.add_constraints_consuming_to tests/type_propagation/deltablue_test.toit
@@ -1136,15 +1136,15 @@ Planner.add_constraints_consuming_to tests/type_propagation/deltablue_test.toit
   1[017] - load local 3
   2[019] - load local 5
   3[005] - load outer S1 // {Null_|EqualityConstraint|ScaleConstraint|EditConstraint|StayConstraint}
-  5[062] - invoke eq // {True_|False_}
+  5[062] - invoke eq // [{*}, {Null_|EqualityConstraint|ScaleConstraint|EditConstraint|StayConstraint}] -> {True_|False_}
   6[081] - branch if true T24
   9[017] - load local 3
- 10[060] - invoke virtual get is_satisfied // {Null_|True_|False_}
+ 10[060] - invoke virtual get is_satisfied // [{*}] -> {Null_|True_|False_}
  13[082] - branch if false T24
  16[002] - pop, load local S3
  18[005] - load outer S4 // {List_}
  20[017] - load local 3
- 21[053] - invoke static List.add <sdk>/core/collections.toit // {Null_}
+ 21[053] - invoke static List.add <sdk>/core/collections.toit // [{List_}, {*}] -> {Null_}
  24[088] - return S1 2
 
 Plan tests/type_propagation/deltablue_test.toit
@@ -1152,10 +1152,10 @@ Plan tests/type_propagation/deltablue_test.toit
   0[016] - load local 2
   1[023] - load smi 0
   2[022] - load null
-  3[053] - invoke static Array_ <sdk>/core/collections.toit // {LargeArray_|SmallArray_}
+  3[053] - invoke static Array_ <sdk>/core/collections.toit // [{SmallInteger_}, {Null_}] -> {LargeArray_|SmallArray_}
   6[014] - load local 0
   7[004] - store local, pop S1
-  9[053] - invoke static create_list_literal_from_array_ <sdk>/core/collections.toit // {List_}
+  9[053] - invoke static create_list_literal_from_array_ <sdk>/core/collections.toit // [{LargeArray_|SmallArray_}] -> {List_}
  12[013] - store field, pop 0
  14[016] - load local 2
  15[088] - return S1 1
@@ -1164,30 +1164,30 @@ Plan.add_constraint tests/type_propagation/deltablue_test.toit
  - argument 0: {Plan}
  - argument 1: {*}
   0[052] - load local, as class, pop 2 - EqualityConstraint(38 - 42) // {True_|False_}
-  2[009] - load field local 3 // {Null_|List_}
+  2[009] - load field local 3 // [{Plan}] -> {Null_|List_}
   4[017] - load local 3
-  5[053] - invoke static List.add <sdk>/core/collections.toit // {Null_}
+  5[053] - invoke static List.add <sdk>/core/collections.toit // [{Null_|List_}, {EqualityConstraint|ScaleConstraint|EditConstraint|StayConstraint}] -> {Null_}
   8[089] - return null S1 2
 
 Plan.execute tests/type_propagation/deltablue_test.toit
  - argument 0: {Plan}
   0[029] - load [block] in Plan.execute tests/type_propagation/deltablue_test.toit
-  5[009] - load field local 3 // {Null_|List_}
+  5[009] - load field local 3 // [{Plan}] -> {Null_|List_}
   7[038] - load block 1
-  9[058] - invoke virtual do // {Null_}
+  9[058] - invoke virtual do // [{Null_|List_}, [block]] -> {Null_}
  13[089] - return null S2 1
 
 [block] in Plan.execute tests/type_propagation/deltablue_test.toit
  - argument 0: [block]
  - argument 1: {*}
   0[016] - load local 2
-  1[058] - invoke virtual execute // {Null_}
+  1[058] - invoke virtual execute // [{*}] -> {Null_}
   5[088] - return S1 2
 
 chain_test tests/type_propagation/deltablue_test.toit
  - argument 0: {SmallInteger_}
   0[042] - allocate instance Planner
-  2[053] - invoke static Planner tests/type_propagation/deltablue_test.toit // {Planner}
+  2[053] - invoke static Planner tests/type_propagation/deltablue_test.toit // [{Planner}] -> {Planner}
   5[035] - store global var G7
   7[041] - pop 1
   8[022] - load null
@@ -1196,32 +1196,32 @@ chain_test tests/type_propagation/deltablue_test.toit
  11[023] - load smi 0
  12[014] - load local 0
  13[000] - load local S7
- 15[065] - invoke lte // {True_|False_}
+ 15[065] - invoke lte // [{LargeInteger_|SmallInteger_}, {SmallInteger_}] -> {True_|False_}
  16[082] - branch if false T83
  19[042] - allocate instance Variable
  21[020] - load literal v
  23[016] - load local 2
- 24[058] - invoke virtual stringify // {String_}
- 28[073] - invoke add // {String_}
+ 24[058] - invoke virtual stringify // [{LargeInteger_|SmallInteger_}] -> {String_}
+ 28[073] - invoke add // [{String_}, {String_}] -> {String_}
  29[023] - load smi 0
- 30[053] - invoke static Variable tests/type_propagation/deltablue_test.toit // {Variable}
+ 30[053] - invoke static Variable tests/type_propagation/deltablue_test.toit // [{Variable}, {String_}, {SmallInteger_}] -> {Variable}
  33[018] - load local 4
  34[082] - branch if false T48
  37[042] - allocate instance EqualityConstraint
  39[033] - load global var lazy G0 // {Strength}
  41[000] - load local S6
  43[017] - load local 3
- 44[053] - invoke static EqualityConstraint tests/type_propagation/deltablue_test.toit // {EqualityConstraint}
+ 44[053] - invoke static EqualityConstraint tests/type_propagation/deltablue_test.toit // [{EqualityConstraint}, {Strength}, {Null_|Variable}, {Variable}] -> {EqualityConstraint}
  47[041] - pop 1
  48[015] - load local 1
  49[023] - load smi 0
- 50[062] - invoke eq // {True_|False_}
+ 50[062] - invoke eq // [{LargeInteger_|SmallInteger_}, {SmallInteger_}] -> {True_|False_}
  51[082] - branch if false T57
  54[014] - load local 0
  55[004] - store local, pop S4
  57[015] - load local 1
  58[000] - load local S8
- 60[062] - invoke eq // {True_|False_}
+ 60[062] - invoke eq // [{LargeInteger_|SmallInteger_}, {SmallInteger_}] -> {True_|False_}
  61[082] - branch if false T67
  64[014] - load local 0
  65[004] - store local, pop S3
@@ -1231,7 +1231,7 @@ chain_test tests/type_propagation/deltablue_test.toit
  71[014] - load local 0
  72[014] - load local 0
  73[025] - load smi 1
- 74[073] - invoke add // {LargeInteger_|SmallInteger_}
+ 74[073] - invoke add // [{LargeInteger_|SmallInteger_}, {SmallInteger_}] -> {LargeInteger_|SmallInteger_}
  75[004] - store local, pop S2
  77[041] - pop 1
  78[083] - branch back T12
@@ -1239,65 +1239,65 @@ chain_test tests/type_propagation/deltablue_test.toit
  84[042] - allocate instance StayConstraint
  86[033] - load global var lazy G3 // {Strength}
  88[016] - load local 2
- 89[053] - invoke static StayConstraint tests/type_propagation/deltablue_test.toit // {StayConstraint}
+ 89[053] - invoke static StayConstraint tests/type_propagation/deltablue_test.toit // [{StayConstraint}, {Strength}, {Null_|Variable}] -> {StayConstraint}
  92[041] - pop 1
  93[042] - allocate instance EditConstraint
  95[033] - load global var lazy G2 // {Strength}
  97[017] - load local 3
- 98[053] - invoke static EditConstraint tests/type_propagation/deltablue_test.toit // {EditConstraint}
+ 98[053] - invoke static EditConstraint tests/type_propagation/deltablue_test.toit // [{EditConstraint}, {Strength}, {Null_|Variable}] -> {EditConstraint}
 101[030] - load global var G7 // {Null_|Planner}
 103[015] - load local 1
-104[053] - invoke static create_array_ <sdk>/core/collections.toit // {LargeArray_|SmallArray_}
-107[053] - invoke static create_list_literal_from_array_ <sdk>/core/collections.toit // {List_}
-110[058] - invoke virtual extract_plan_from_constraints // {Plan}
+104[053] - invoke static create_array_ <sdk>/core/collections.toit // [{EditConstraint}] -> {LargeArray_|SmallArray_}
+107[053] - invoke static create_list_literal_from_array_ <sdk>/core/collections.toit // [{LargeArray_|SmallArray_}] -> {List_}
+110[058] - invoke virtual extract_plan_from_constraints // [{Null_|Planner}, {List_}] -> {Plan}
 114[023] - load smi 0
 115[014] - load local 0
 116[026] - load smi 100
-118[063] - invoke lt // {True_|False_}
+118[063] - invoke lt // [{LargeInteger_|SmallInteger_}, {SmallInteger_}] -> {True_|False_}
 119[082] - branch if false T205
 122[018] - load local 4
 123[015] - load local 1
-124[061] - invoke virtual set value // {LargeInteger_|SmallInteger_}
+124[061] - invoke virtual set value // [{Null_|Variable}, {LargeInteger_|SmallInteger_}] -> {LargeInteger_|SmallInteger_}
 127[002] - pop, load local S1
-129[053] - invoke static Plan.execute tests/type_propagation/deltablue_test.toit // {Null_}
+129[053] - invoke static Plan.execute tests/type_propagation/deltablue_test.toit // [{Plan}] -> {Null_}
 132[002] - pop, load local S3
-134[060] - invoke virtual get value // {Null_|LargeInteger_|SmallInteger_}
+134[060] - invoke virtual get value // [{Null_|Variable}] -> {Null_|LargeInteger_|SmallInteger_}
 137[015] - load local 1
-138[062] - invoke eq // {True_|False_}
+138[062] - invoke eq // [{Null_|LargeInteger_|SmallInteger_}, {LargeInteger_|SmallInteger_}] -> {True_|False_}
 139[081] - branch if true T193
 142[026] - load smi 5
 144[022] - load null
-145[053] - invoke static Array_ <sdk>/core/collections.toit // {LargeArray_|SmallArray_}
+145[053] - invoke static Array_ <sdk>/core/collections.toit // [{SmallInteger_}, {Null_}] -> {LargeArray_|SmallArray_}
 148[014] - load local 0
 149[023] - load smi 0
 150[020] - load literal Chain test failed: 
-152[079] - invoke at_put // {*}
+152[079] - invoke at_put // [{LargeArray_|SmallArray_}, {SmallInteger_}, {String_}] -> {*}
 153[002] - pop, load local S0
 155[025] - load smi 1
 156[000] - load local S6
-158[060] - invoke virtual get value // {Null_|LargeInteger_|SmallInteger_}
-161[079] - invoke at_put // {*}
+158[060] - invoke virtual get value // [{Null_|Variable}] -> {Null_|LargeInteger_|SmallInteger_}
+161[079] - invoke at_put // [{LargeArray_|SmallArray_}, {SmallInteger_}, {Null_|LargeInteger_|SmallInteger_}] -> {*}
 162[002] - pop, load local S0
 164[026] - load smi 2
 166[020] - load literal  != 
-168[079] - invoke at_put // {*}
+168[079] - invoke at_put // [{LargeArray_|SmallArray_}, {SmallInteger_}, {String_}] -> {*}
 169[002] - pop, load local S0
 171[026] - load smi 3
 173[017] - load local 3
-174[079] - invoke at_put // {*}
+174[079] - invoke at_put // [{LargeArray_|SmallArray_}, {SmallInteger_}, {LargeInteger_|SmallInteger_}] -> {*}
 175[002] - pop, load local S0
 177[026] - load smi 4
 179[020] - load literal 
-181[079] - invoke at_put // {*}
+181[079] - invoke at_put // [{LargeArray_|SmallArray_}, {SmallInteger_}, {String_}] -> {*}
 182[002] - pop, load local S0
 184[004] - store local, pop S1
-186[053] - invoke static simple_interpolate_strings_ <sdk>/core/utils.toit // {String_}
-189[053] - invoke static throw <sdk>/core/exceptions.toit // {}
+186[053] - invoke static simple_interpolate_strings_ <sdk>/core/utils.toit // [{LargeArray_|SmallArray_}] -> {String_}
+189[053] - invoke static throw <sdk>/core/exceptions.toit // [{String_}] -> {}
 192[041] - pop 1
 193[014] - load local 0
 194[014] - load local 0
 195[025] - load smi 1
-196[073] - invoke add // {LargeInteger_|SmallInteger_}
+196[073] - invoke add // [{LargeInteger_|SmallInteger_}, {SmallInteger_}] -> {LargeInteger_|SmallInteger_}
 197[004] - store local, pop S2
 199[041] - pop 1
 200[083] - branch back T115
@@ -1306,54 +1306,54 @@ chain_test tests/type_propagation/deltablue_test.toit
 projection_test tests/type_propagation/deltablue_test.toit
  - argument 0: {SmallInteger_}
   0[042] - allocate instance Planner
-  2[053] - invoke static Planner tests/type_propagation/deltablue_test.toit // {Planner}
+  2[053] - invoke static Planner tests/type_propagation/deltablue_test.toit // [{Planner}] -> {Planner}
   5[035] - store global var G7
   7[041] - pop 1
   8[042] - allocate instance Variable
  10[020] - load literal scale
  12[026] - load smi 10
- 14[053] - invoke static Variable tests/type_propagation/deltablue_test.toit // {Variable}
+ 14[053] - invoke static Variable tests/type_propagation/deltablue_test.toit // [{Variable}, {String_}, {SmallInteger_}] -> {Variable}
  17[042] - allocate instance Variable
  19[020] - load literal offset
  21[027] - load smi 1000
- 24[053] - invoke static Variable tests/type_propagation/deltablue_test.toit // {Variable}
+ 24[053] - invoke static Variable tests/type_propagation/deltablue_test.toit // [{Variable}, {String_}, {SmallInteger_}] -> {Variable}
  27[022] - load null
  28[022] - load null
  29[023] - load smi 0
  30[022] - load null
- 31[053] - invoke static Array_ <sdk>/core/collections.toit // {LargeArray_|SmallArray_}
+ 31[053] - invoke static Array_ <sdk>/core/collections.toit // [{SmallInteger_}, {Null_}] -> {LargeArray_|SmallArray_}
  34[014] - load local 0
  35[004] - store local, pop S1
- 37[053] - invoke static create_list_literal_from_array_ <sdk>/core/collections.toit // {List_}
+ 37[053] - invoke static create_list_literal_from_array_ <sdk>/core/collections.toit // [{LargeArray_|SmallArray_}] -> {List_}
  40[023] - load smi 0
  41[014] - load local 0
  42[000] - load local S9
- 44[063] - invoke lt // {True_|False_}
+ 44[063] - invoke lt // [{LargeInteger_|SmallInteger_}, {SmallInteger_}] -> {True_|False_}
  45[082] - branch if false T121
  48[042] - allocate instance Variable
  50[020] - load literal src
  52[016] - load local 2
- 53[058] - invoke virtual stringify // {String_}
- 57[073] - invoke add // {String_}
+ 53[058] - invoke virtual stringify // [{LargeInteger_|SmallInteger_}] -> {String_}
+ 57[073] - invoke add // [{String_}, {String_}] -> {String_}
  58[016] - load local 2
- 59[053] - invoke static Variable tests/type_propagation/deltablue_test.toit // {Variable}
+ 59[053] - invoke static Variable tests/type_propagation/deltablue_test.toit // [{Variable}, {String_}, {LargeInteger_|SmallInteger_}] -> {Variable}
  62[004] - store local, pop S4
  64[042] - allocate instance Variable
  66[020] - load literal dst
  68[016] - load local 2
- 69[058] - invoke virtual stringify // {String_}
- 73[073] - invoke add // {String_}
+ 69[058] - invoke virtual stringify // [{LargeInteger_|SmallInteger_}] -> {String_}
+ 73[073] - invoke add // [{String_}, {String_}] -> {String_}
  74[016] - load local 2
- 75[053] - invoke static Variable tests/type_propagation/deltablue_test.toit // {Variable}
+ 75[053] - invoke static Variable tests/type_propagation/deltablue_test.toit // [{Variable}, {String_}, {LargeInteger_|SmallInteger_}] -> {Variable}
  78[004] - store local, pop S3
  80[015] - load local 1
  81[017] - load local 3
- 82[053] - invoke static List.add <sdk>/core/collections.toit // {Null_}
+ 82[053] - invoke static List.add <sdk>/core/collections.toit // [{List_}, {Variable}] -> {Null_}
  85[041] - pop 1
  86[042] - allocate instance StayConstraint
  88[033] - load global var lazy G4 // {Strength}
  90[019] - load local 5
- 91[053] - invoke static StayConstraint tests/type_propagation/deltablue_test.toit // {StayConstraint}
+ 91[053] - invoke static StayConstraint tests/type_propagation/deltablue_test.toit // [{StayConstraint}, {Strength}, {Variable}] -> {StayConstraint}
  94[041] - pop 1
  95[042] - allocate instance ScaleConstraint
  97[033] - load global var lazy G0 // {Strength}
@@ -1361,98 +1361,98 @@ projection_test tests/type_propagation/deltablue_test.toit
 100[019] - load local 5
 101[000] - load local S9
 103[000] - load local S9
-105[053] - invoke static ScaleConstraint tests/type_propagation/deltablue_test.toit // {ScaleConstraint}
+105[053] - invoke static ScaleConstraint tests/type_propagation/deltablue_test.toit // [{ScaleConstraint}, {Strength}, {Variable}, {Variable}, {Variable}, {Variable}] -> {ScaleConstraint}
 108[041] - pop 1
 109[014] - load local 0
 110[014] - load local 0
 111[025] - load smi 1
-112[073] - invoke add // {LargeInteger_|SmallInteger_}
+112[073] - invoke add // [{LargeInteger_|SmallInteger_}, {SmallInteger_}] -> {LargeInteger_|SmallInteger_}
 113[004] - store local, pop S2
 115[041] - pop 1
 116[083] - branch back T41
 121[002] - pop, load local S2
 123[026] - load smi 17
-125[053] - invoke static change tests/type_propagation/deltablue_test.toit // {Null_}
+125[053] - invoke static change tests/type_propagation/deltablue_test.toit // [{Null_|Variable}, {SmallInteger_}] -> {Null_}
 128[002] - pop, load local S1
-130[060] - invoke virtual get value // {Null_|LargeInteger_|SmallInteger_}
+130[060] - invoke virtual get value // [{Null_|Variable}] -> {Null_|LargeInteger_|SmallInteger_}
 133[027] - load smi 1170
-136[062] - invoke eq // {True_|False_}
+136[062] - invoke eq // [{Null_|LargeInteger_|SmallInteger_}, {SmallInteger_}] -> {True_|False_}
 137[081] - branch if true T146
 140[020] - load literal Projection 1 failed
-142[053] - invoke static throw <sdk>/core/exceptions.toit // {}
+142[053] - invoke static throw <sdk>/core/exceptions.toit // [{String_}] -> {}
 145[041] - pop 1
 146[015] - load local 1
 147[027] - load smi 1050
-150[053] - invoke static change tests/type_propagation/deltablue_test.toit // {Null_}
+150[053] - invoke static change tests/type_propagation/deltablue_test.toit // [{Null_|Variable}, {SmallInteger_}] -> {Null_}
 153[002] - pop, load local S2
-155[060] - invoke virtual get value // {Null_|LargeInteger_|SmallInteger_}
+155[060] - invoke virtual get value // [{Null_|Variable}] -> {Null_|LargeInteger_|SmallInteger_}
 158[026] - load smi 5
-160[062] - invoke eq // {True_|False_}
+160[062] - invoke eq // [{Null_|LargeInteger_|SmallInteger_}, {SmallInteger_}] -> {True_|False_}
 161[081] - branch if true T170
 164[020] - load literal Projection 2 failed
-166[053] - invoke static throw <sdk>/core/exceptions.toit // {}
+166[053] - invoke static throw <sdk>/core/exceptions.toit // [{String_}] -> {}
 169[041] - pop 1
 170[018] - load local 4
 171[026] - load smi 5
-173[053] - invoke static change tests/type_propagation/deltablue_test.toit // {Null_}
+173[053] - invoke static change tests/type_propagation/deltablue_test.toit // [{Variable}, {SmallInteger_}] -> {Null_}
 176[041] - pop 1
 177[023] - load smi 0
 178[014] - load local 0
 179[000] - load local S9
 181[025] - load smi 1
-182[074] - invoke sub // {LargeInteger_|SmallInteger_}
-183[063] - invoke lt // {True_|False_}
+182[074] - invoke sub // [{SmallInteger_}, {SmallInteger_}] -> {LargeInteger_|SmallInteger_}
+183[063] - invoke lt // [{LargeInteger_|SmallInteger_}, {LargeInteger_|SmallInteger_}] -> {True_|False_}
 184[082] - branch if false T223
 187[015] - load local 1
 188[015] - load local 1
-189[078] - invoke at // {*}
-190[060] - invoke virtual get value // {*}
+189[078] - invoke at // [{List_}, {LargeInteger_|SmallInteger_}] -> {*}
+190[060] - invoke virtual get value // [{*}] -> {*}
 193[015] - load local 1
 194[026] - load smi 5
-196[075] - invoke mul // {LargeInteger_|SmallInteger_}
+196[075] - invoke mul // [{LargeInteger_|SmallInteger_}, {SmallInteger_}] -> {LargeInteger_|SmallInteger_}
 197[027] - load smi 1000
-200[073] - invoke add // {LargeInteger_|SmallInteger_}
-201[062] - invoke eq // {True_|False_}
+200[073] - invoke add // [{LargeInteger_|SmallInteger_}, {SmallInteger_}] -> {LargeInteger_|SmallInteger_}
+201[062] - invoke eq // [{*}, {LargeInteger_|SmallInteger_}] -> {True_|False_}
 202[081] - branch if true T211
 205[020] - load literal Projection 3 failed
-207[053] - invoke static throw <sdk>/core/exceptions.toit // {}
+207[053] - invoke static throw <sdk>/core/exceptions.toit // [{String_}] -> {}
 210[041] - pop 1
 211[014] - load local 0
 212[014] - load local 0
 213[025] - load smi 1
-214[073] - invoke add // {LargeInteger_|SmallInteger_}
+214[073] - invoke add // [{LargeInteger_|SmallInteger_}, {SmallInteger_}] -> {LargeInteger_|SmallInteger_}
 215[004] - store local, pop S2
 217[041] - pop 1
 218[083] - branch back T178
 223[002] - pop, load local S3
 225[027] - load smi 2000
-228[053] - invoke static change tests/type_propagation/deltablue_test.toit // {Null_}
+228[053] - invoke static change tests/type_propagation/deltablue_test.toit // [{Variable}, {SmallInteger_}] -> {Null_}
 231[041] - pop 1
 232[023] - load smi 0
 233[014] - load local 0
 234[000] - load local S9
 236[025] - load smi 1
-237[074] - invoke sub // {LargeInteger_|SmallInteger_}
-238[063] - invoke lt // {True_|False_}
+237[074] - invoke sub // [{SmallInteger_}, {SmallInteger_}] -> {LargeInteger_|SmallInteger_}
+238[063] - invoke lt // [{LargeInteger_|SmallInteger_}, {LargeInteger_|SmallInteger_}] -> {True_|False_}
 239[082] - branch if false T278
 242[015] - load local 1
 243[015] - load local 1
-244[078] - invoke at // {*}
-245[060] - invoke virtual get value // {*}
+244[078] - invoke at // [{List_}, {LargeInteger_|SmallInteger_}] -> {*}
+245[060] - invoke virtual get value // [{*}] -> {*}
 248[015] - load local 1
 249[026] - load smi 5
-251[075] - invoke mul // {LargeInteger_|SmallInteger_}
+251[075] - invoke mul // [{LargeInteger_|SmallInteger_}, {SmallInteger_}] -> {LargeInteger_|SmallInteger_}
 252[027] - load smi 2000
-255[073] - invoke add // {LargeInteger_|SmallInteger_}
-256[062] - invoke eq // {True_|False_}
+255[073] - invoke add // [{LargeInteger_|SmallInteger_}, {SmallInteger_}] -> {LargeInteger_|SmallInteger_}
+256[062] - invoke eq // [{*}, {LargeInteger_|SmallInteger_}] -> {True_|False_}
 257[081] - branch if true T266
 260[020] - load literal Projection 4 failed
-262[053] - invoke static throw <sdk>/core/exceptions.toit // {}
+262[053] - invoke static throw <sdk>/core/exceptions.toit // [{String_}] -> {}
 265[041] - pop 1
 266[014] - load local 0
 267[014] - load local 0
 268[025] - load smi 1
-269[073] - invoke add // {LargeInteger_|SmallInteger_}
+269[073] - invoke add // [{LargeInteger_|SmallInteger_}, {SmallInteger_}] -> {LargeInteger_|SmallInteger_}
 270[004] - store local, pop S2
 272[041] - pop 1
 273[083] - branch back T233
@@ -1465,19 +1465,19 @@ change tests/type_propagation/deltablue_test.toit
   2[042] - allocate instance EditConstraint
   4[033] - load global var lazy G2 // {Strength}
   6[019] - load local 5
-  7[053] - invoke static EditConstraint tests/type_propagation/deltablue_test.toit // {EditConstraint}
+  7[053] - invoke static EditConstraint tests/type_propagation/deltablue_test.toit // [{EditConstraint}, {Strength}, {Variable}] -> {EditConstraint}
  10[030] - load global var G7 // {Null_|Planner}
  12[015] - load local 1
- 13[053] - invoke static create_array_ <sdk>/core/collections.toit // {LargeArray_|SmallArray_}
- 16[053] - invoke static create_list_literal_from_array_ <sdk>/core/collections.toit // {List_}
- 19[058] - invoke virtual extract_plan_from_constraints // {Plan}
+ 13[053] - invoke static create_array_ <sdk>/core/collections.toit // [{EditConstraint}] -> {LargeArray_|SmallArray_}
+ 16[053] - invoke static create_list_literal_from_array_ <sdk>/core/collections.toit // [{LargeArray_|SmallArray_}] -> {List_}
+ 19[058] - invoke virtual extract_plan_from_constraints // [{Null_|Planner}, {List_}] -> {Plan}
  23[029] - load [block] in change tests/type_propagation/deltablue_test.toit
  28[026] - load smi 10
  30[038] - load block 1
- 32[058] - invoke virtual repeat // {Null_}
+ 32[058] - invoke virtual repeat // [{SmallInteger_}, [block]] -> {Null_}
  36[041] - pop 1
  37[002] - pop, load local S1
- 39[053] - invoke static Constraint.destroy_constraint tests/type_propagation/deltablue_test.toit // {Null_}
+ 39[053] - invoke static Constraint.destroy_constraint tests/type_propagation/deltablue_test.toit // [{EditConstraint}] -> {Null_}
  42[089] - return null S3 2
 
 [block] in change tests/type_propagation/deltablue_test.toit
@@ -1489,5 +1489,5 @@ change tests/type_propagation/deltablue_test.toit
   6[013] - store field, pop 1
   8[016] - load local 2
   9[005] - load outer S1 // {Plan}
- 11[053] - invoke static Plan.execute tests/type_propagation/deltablue_test.toit // {Null_}
+ 11[053] - invoke static Plan.execute tests/type_propagation/deltablue_test.toit // [{Plan}] -> {Null_}
  14[088] - return S1 1
diff --git a/tests/type_propagation/gold/field_test.gold b/tests/type_propagation/gold/field_test.gold
index 05180fd63..7c6bd23c4 100644
--- a/tests/type_propagation/gold/field_test.gold
+++ b/tests/type_propagation/gold/field_test.gold
@@ -5,27 +5,27 @@ main tests/type_propagation/field_test.toit
 test_simple tests/type_propagation/field_test.toit
   0[042] - allocate instance A
   2[026] - load smi 12
-  4[053] - invoke static A tests/type_propagation/field_test.toit // {A}
+  4[053] - invoke static A tests/type_propagation/field_test.toit // [{A}, {SmallInteger_}] -> {A}
   7[014] - load local 0
-  8[060] - invoke virtual get x // {String_|Null_|SmallInteger_}
- 11[053] - invoke static id tests/type_propagation/field_test.toit // {String_|Null_|SmallInteger_}
+  8[060] - invoke virtual get x // [{A}] -> {String_|Null_|SmallInteger_}
+ 11[053] - invoke static id tests/type_propagation/field_test.toit // [{String_|Null_|SmallInteger_}] -> {String_|Null_|SmallInteger_}
  14[041] - pop 1
  15[042] - allocate instance A
  17[020] - load literal horse
- 19[053] - invoke static A tests/type_propagation/field_test.toit // {A}
+ 19[053] - invoke static A tests/type_propagation/field_test.toit // [{A}, {String_}] -> {A}
  22[004] - store local, pop S1
  24[014] - load local 0
- 25[060] - invoke virtual get x // {String_|Null_|SmallInteger_}
- 28[053] - invoke static id tests/type_propagation/field_test.toit // {String_|Null_|SmallInteger_}
+ 25[060] - invoke virtual get x // [{A}] -> {String_|Null_|SmallInteger_}
+ 28[053] - invoke static id tests/type_propagation/field_test.toit // [{String_|Null_|SmallInteger_}] -> {String_|Null_|SmallInteger_}
  31[041] - pop 1
  32[042] - allocate instance B
  34[020] - load literal true
  36[026] - load smi 42
- 38[053] - invoke static B tests/type_propagation/field_test.toit // {B}
- 41[009] - load field local 0 // {Null_|True_}
- 43[053] - invoke static id tests/type_propagation/field_test.toit // {Null_|True_}
- 46[010] - pop, load field local 16 // {Null_|SmallInteger_}
- 48[053] - invoke static id tests/type_propagation/field_test.toit // {Null_|SmallInteger_}
+ 38[053] - invoke static B tests/type_propagation/field_test.toit // [{B}, {True_}, {SmallInteger_}] -> {B}
+ 41[009] - load field local 0 // [{B}] -> {Null_|True_}
+ 43[053] - invoke static id tests/type_propagation/field_test.toit // [{Null_|True_}] -> {Null_|True_}
+ 46[010] - pop, load field local 16 // [{B}] -> {Null_|SmallInteger_}
+ 48[053] - invoke static id tests/type_propagation/field_test.toit // [{Null_|SmallInteger_}] -> {Null_|SmallInteger_}
  51[089] - return null S3 0
 
 id tests/type_propagation/field_test.toit
@@ -35,7 +35,7 @@ id tests/type_propagation/field_test.toit
 
 A.x tests/type_propagation/field_test.toit
  - argument 0: {A}
-  0[009] - load field local 2 // {String_|Null_|SmallInteger_}
+  0[009] - load field local 2 // [{A}] -> {String_|Null_|SmallInteger_}
   2[088] - return S1 1
 
 A tests/type_propagation/field_test.toit
@@ -56,6 +56,6 @@ B tests/type_propagation/field_test.toit
   2[013] - store field, pop 1
   4[018] - load local 4
   5[018] - load local 4
-  6[053] - invoke static A tests/type_propagation/field_test.toit // {B}
+  6[053] - invoke static A tests/type_propagation/field_test.toit // [{B}, {True_}] -> {B}
   9[002] - pop, load local S4
  11[088] - return S1 3
diff --git a/tests/type_propagation/gold/field_test.gold-O2 b/tests/type_propagation/gold/field_test.gold-O2
index 05180fd63..7c6bd23c4 100644
--- a/tests/type_propagation/gold/field_test.gold-O2
+++ b/tests/type_propagation/gold/field_test.gold-O2
@@ -5,27 +5,27 @@ main tests/type_propagation/field_test.toit
 test_simple tests/type_propagation/field_test.toit
   0[042] - allocate instance A
   2[026] - load smi 12
-  4[053] - invoke static A tests/type_propagation/field_test.toit // {A}
+  4[053] - invoke static A tests/type_propagation/field_test.toit // [{A}, {SmallInteger_}] -> {A}
   7[014] - load local 0
-  8[060] - invoke virtual get x // {String_|Null_|SmallInteger_}
- 11[053] - invoke static id tests/type_propagation/field_test.toit // {String_|Null_|SmallInteger_}
+  8[060] - invoke virtual get x // [{A}] -> {String_|Null_|SmallInteger_}
+ 11[053] - invoke static id tests/type_propagation/field_test.toit // [{String_|Null_|SmallInteger_}] -> {String_|Null_|SmallInteger_}
  14[041] - pop 1
  15[042] - allocate instance A
  17[020] - load literal horse
- 19[053] - invoke static A tests/type_propagation/field_test.toit // {A}
+ 19[053] - invoke static A tests/type_propagation/field_test.toit // [{A}, {String_}] -> {A}
  22[004] - store local, pop S1
  24[014] - load local 0
- 25[060] - invoke virtual get x // {String_|Null_|SmallInteger_}
- 28[053] - invoke static id tests/type_propagation/field_test.toit // {String_|Null_|SmallInteger_}
+ 25[060] - invoke virtual get x // [{A}] -> {String_|Null_|SmallInteger_}
+ 28[053] - invoke static id tests/type_propagation/field_test.toit // [{String_|Null_|SmallInteger_}] -> {String_|Null_|SmallInteger_}
  31[041] - pop 1
  32[042] - allocate instance B
  34[020] - load literal true
  36[026] - load smi 42
- 38[053] - invoke static B tests/type_propagation/field_test.toit // {B}
- 41[009] - load field local 0 // {Null_|True_}
- 43[053] - invoke static id tests/type_propagation/field_test.toit // {Null_|True_}
- 46[010] - pop, load field local 16 // {Null_|SmallInteger_}
- 48[053] - invoke static id tests/type_propagation/field_test.toit // {Null_|SmallInteger_}
+ 38[053] - invoke static B tests/type_propagation/field_test.toit // [{B}, {True_}, {SmallInteger_}] -> {B}
+ 41[009] - load field local 0 // [{B}] -> {Null_|True_}
+ 43[053] - invoke static id tests/type_propagation/field_test.toit // [{Null_|True_}] -> {Null_|True_}
+ 46[010] - pop, load field local 16 // [{B}] -> {Null_|SmallInteger_}
+ 48[053] - invoke static id tests/type_propagation/field_test.toit // [{Null_|SmallInteger_}] -> {Null_|SmallInteger_}
  51[089] - return null S3 0
 
 id tests/type_propagation/field_test.toit
@@ -35,7 +35,7 @@ id tests/type_propagation/field_test.toit
 
 A.x tests/type_propagation/field_test.toit
  - argument 0: {A}
-  0[009] - load field local 2 // {String_|Null_|SmallInteger_}
+  0[009] - load field local 2 // [{A}] -> {String_|Null_|SmallInteger_}
   2[088] - return S1 1
 
 A tests/type_propagation/field_test.toit
@@ -56,6 +56,6 @@ B tests/type_propagation/field_test.toit
   2[013] - store field, pop 1
   4[018] - load local 4
   5[018] - load local 4
-  6[053] - invoke static A tests/type_propagation/field_test.toit // {B}
+  6[053] - invoke static A tests/type_propagation/field_test.toit // [{B}, {True_}] -> {B}
   9[002] - pop, load local S4
  11[088] - return S1 3
diff --git a/tests/type_propagation/gold/finally_test.gold b/tests/type_propagation/gold/finally_test.gold
index e09a2a781..009b140dc 100644
--- a/tests/type_propagation/gold/finally_test.gold
+++ b/tests/type_propagation/gold/finally_test.gold
@@ -15,12 +15,12 @@ test_is_exception tests/type_propagation/finally_test.toit
   5[029] - load [block] in test_is_exception tests/type_propagation/finally_test.toit
  10[094] - link try 0
  12[038] - load block 4
- 14[055] - invoke block S1 // {Null_}
+ 14[055] - invoke block S1 // [[block]] -> {Null_}
  16[041] - pop 1
  17[095] - unlink try 0
  19[020] - load literal -2
  21[015] - load local 1
- 22[062] - invoke eq // {True_|False_}
+ 22[062] - invoke eq // [{SmallInteger_}, {SmallInteger_}] -> {True_|False_}
  23[022] - load null
  24[015] - load local 1
  25[082] - branch if false T30
@@ -30,7 +30,7 @@ test_is_exception tests/type_propagation/finally_test.toit
  33[040] - pop 2
  35[096] - unwind
  36[002] - pop, load local S0
- 38[053] - invoke static id tests/type_propagation/finally_test.toit // {True_|False_}
+ 38[053] - invoke static id tests/type_propagation/finally_test.toit // [{True_|False_}] -> {True_|False_}
  41[089] - return null S2 0
 
 [block] in test_is_exception tests/type_propagation/finally_test.toit
@@ -42,12 +42,12 @@ return_is_exception tests/type_propagation/finally_test.toit
   0[029] - load [block] in return_is_exception tests/type_propagation/finally_test.toit
   5[094] - link try 0
   7[038] - load block 4
-  9[055] - invoke block S1 // {Null_}
+  9[055] - invoke block S1 // [[block]] -> {Null_}
  11[041] - pop 1
  12[095] - unlink try 0
  14[020] - load literal -2
  16[015] - load local 1
- 17[062] - invoke eq // {True_|False_}
+ 17[062] - invoke eq // [{SmallInteger_}, {SmallInteger_}] -> {True_|False_}
  18[022] - load null
  19[015] - load local 1
  20[082] - branch if false T25
@@ -69,12 +69,12 @@ test_exception tests/type_propagation/finally_test.toit
   5[029] - load [block] in test_exception tests/type_propagation/finally_test.toit
  10[094] - link try 0
  12[038] - load block 4
- 14[055] - invoke block S1 // {Null_}
+ 14[055] - invoke block S1 // [[block]] -> {Null_}
  16[041] - pop 1
  17[095] - unlink try 0
  19[020] - load literal -2
  21[015] - load local 1
- 22[062] - invoke eq // {True_|False_}
+ 22[062] - invoke eq // [{SmallInteger_}, {SmallInteger_}] -> {True_|False_}
  23[022] - load null
  24[015] - load local 1
  25[082] - branch if false T30
@@ -84,7 +84,7 @@ test_exception tests/type_propagation/finally_test.toit
  33[040] - pop 2
  35[096] - unwind
  36[002] - pop, load local S0
- 38[053] - invoke static id tests/type_propagation/finally_test.toit // {Null_|Exception_}
+ 38[053] - invoke static id tests/type_propagation/finally_test.toit // [{Null_|Exception_}] -> {Null_|Exception_}
  41[089] - return null S2 0
 
 [block] in test_exception tests/type_propagation/finally_test.toit
@@ -96,12 +96,12 @@ return_exception tests/type_propagation/finally_test.toit
   0[029] - load [block] in return_exception tests/type_propagation/finally_test.toit
   5[094] - link try 0
   7[038] - load block 4
-  9[055] - invoke block S1 // {Null_}
+  9[055] - invoke block S1 // [[block]] -> {Null_}
  11[041] - pop 1
  12[095] - unlink try 0
  14[020] - load literal -2
  16[015] - load local 1
- 17[062] - invoke eq // {True_|False_}
+ 17[062] - invoke eq // [{SmallInteger_}, {SmallInteger_}] -> {True_|False_}
  18[022] - load null
  19[015] - load local 1
  20[082] - branch if false T25
@@ -124,12 +124,12 @@ catchy tests/type_propagation/finally_test.toit
   0[029] - load [block] in catchy tests/type_propagation/finally_test.toit
   5[094] - link try 0
   7[038] - load block 4
-  9[055] - invoke block S1 // {}
+  9[055] - invoke block S1 // [[block]] -> {}
  11[041] - pop 1
  12[095] - unlink try 0
  14[020] - load literal -2
  16[015] - load local 1
- 17[062] - invoke eq // {True_|False_}
+ 17[062] - invoke eq // [{SmallInteger_}, {SmallInteger_}] -> {True_|False_}
  18[022] - load null
  19[015] - load local 1
  20[082] - branch if false T25
@@ -151,11 +151,11 @@ test_nlb_out_of_try tests/type_propagation/finally_test.toit
   2[029] - load [block] in test_nlb_out_of_try tests/type_propagation/finally_test.toit
   7[094] - link try 0
   9[038] - load block 4
- 11[055] - invoke block S1 // {Null_}
+ 11[055] - invoke block S1 // [[block]] -> {Null_}
  13[041] - pop 1
  14[095] - unlink try 0
  16[018] - load local 4
- 17[053] - invoke static id tests/type_propagation/finally_test.toit // {String_|Null_|SmallInteger_}
+ 17[053] - invoke static id tests/type_propagation/finally_test.toit // [{String_|Null_|SmallInteger_}] -> {String_|Null_|SmallInteger_}
  20[041] - pop 1
  21[096] - unwind
  22[089] - return null S2 0
@@ -164,7 +164,7 @@ test_nlb_out_of_try tests/type_propagation/finally_test.toit
  - argument 0: [block]
   0[029] - load [block] in [block] in test_nlb_out_of_try tests/type_propagation/finally_test.toit
   5[038] - load block 0
-  7[053] - invoke static invoke tests/type_propagation/finally_test.toit // {}
+  7[053] - invoke static invoke tests/type_propagation/finally_test.toit // [[block]] -> {}
  10[040] - pop 2
  12[083] - branch back T0
  17[016] - load local 2
@@ -175,7 +175,7 @@ test_nlb_out_of_try tests/type_propagation/finally_test.toit
  26[082] - branch if false T41
  29[029] - load [block] in [block] in test_nlb_out_of_try tests/type_propagation/finally_test.toit
  34[038] - load block 0
- 36[053] - invoke static invoke tests/type_propagation/finally_test.toit // {}
+ 36[053] - invoke static invoke tests/type_propagation/finally_test.toit // [[block]] -> {}
  39[040] - pop 2
  41[016] - load local 2
  42[022] - load null
@@ -203,13 +203,13 @@ id tests/type_propagation/finally_test.toit
 
 pick tests/type_propagation/finally_test.toit
   0[026] - load smi 100
-  2[053] - invoke static random <sdk>/core/utils.toit // {LargeInteger_|SmallInteger_}
+  2[053] - invoke static random <sdk>/core/utils.toit // [{SmallInteger_}] -> {LargeInteger_|SmallInteger_}
   5[026] - load smi 50
-  7[063] - invoke lt // {True_|False_}
+  7[063] - invoke lt // [{LargeInteger_|SmallInteger_}, {SmallInteger_}] -> {True_|False_}
   8[088] - return S1 0
 
 invoke tests/type_propagation/finally_test.toit
  - argument 0: [block]
   0[016] - load local 2
-  1[055] - invoke block S1 // {}
+  1[055] - invoke block S1 // [[block]] -> {}
   3[089] - return null S1 1
diff --git a/tests/type_propagation/gold/finally_test.gold-O2 b/tests/type_propagation/gold/finally_test.gold-O2
index b246485c1..0c5a13ae3 100644
--- a/tests/type_propagation/gold/finally_test.gold-O2
+++ b/tests/type_propagation/gold/finally_test.gold-O2
@@ -15,12 +15,12 @@ test_is_exception tests/type_propagation/finally_test.toit
   5[029] - load [block] in test_is_exception tests/type_propagation/finally_test.toit
  10[094] - link try 0
  12[038] - load block 4
- 14[055] - invoke block S1 // {Null_}
+ 14[055] - invoke block S1 // [[block]] -> {Null_}
  16[041] - pop 1
  17[095] - unlink try 0
  19[020] - load literal -2
  21[015] - load local 1
- 22[062] - invoke eq // {True_|False_}
+ 22[062] - invoke eq // [{SmallInteger_}, {SmallInteger_}] -> {True_|False_}
  23[022] - load null
  24[015] - load local 1
  25[082] - branch if false T30
@@ -30,7 +30,7 @@ test_is_exception tests/type_propagation/finally_test.toit
  33[040] - pop 2
  35[096] - unwind
  36[002] - pop, load local S0
- 38[053] - invoke static id tests/type_propagation/finally_test.toit // {True_|False_}
+ 38[053] - invoke static id tests/type_propagation/finally_test.toit // [{True_|False_}] -> {True_|False_}
  41[089] - return null S2 0
 
 [block] in test_is_exception tests/type_propagation/finally_test.toit
@@ -42,12 +42,12 @@ return_is_exception tests/type_propagation/finally_test.toit
   0[029] - load [block] in return_is_exception tests/type_propagation/finally_test.toit
   5[094] - link try 0
   7[038] - load block 4
-  9[055] - invoke block S1 // {Null_}
+  9[055] - invoke block S1 // [[block]] -> {Null_}
  11[041] - pop 1
  12[095] - unlink try 0
  14[020] - load literal -2
  16[015] - load local 1
- 17[062] - invoke eq // {True_|False_}
+ 17[062] - invoke eq // [{SmallInteger_}, {SmallInteger_}] -> {True_|False_}
  18[022] - load null
  19[015] - load local 1
  20[082] - branch if false T25
@@ -69,12 +69,12 @@ test_exception tests/type_propagation/finally_test.toit
   5[029] - load [block] in test_exception tests/type_propagation/finally_test.toit
  10[094] - link try 0
  12[038] - load block 4
- 14[055] - invoke block S1 // {Null_}
+ 14[055] - invoke block S1 // [[block]] -> {Null_}
  16[041] - pop 1
  17[095] - unlink try 0
  19[020] - load literal -2
  21[015] - load local 1
- 22[062] - invoke eq // {True_|False_}
+ 22[062] - invoke eq // [{SmallInteger_}, {SmallInteger_}] -> {True_|False_}
  23[022] - load null
  24[015] - load local 1
  25[082] - branch if false T30
@@ -84,7 +84,7 @@ test_exception tests/type_propagation/finally_test.toit
  33[040] - pop 2
  35[096] - unwind
  36[002] - pop, load local S0
- 38[053] - invoke static id tests/type_propagation/finally_test.toit // {Null_|Exception_}
+ 38[053] - invoke static id tests/type_propagation/finally_test.toit // [{Null_|Exception_}] -> {Null_|Exception_}
  41[089] - return null S2 0
 
 [block] in test_exception tests/type_propagation/finally_test.toit
@@ -96,12 +96,12 @@ return_exception tests/type_propagation/finally_test.toit
   0[029] - load [block] in return_exception tests/type_propagation/finally_test.toit
   5[094] - link try 0
   7[038] - load block 4
-  9[055] - invoke block S1 // {Null_}
+  9[055] - invoke block S1 // [[block]] -> {Null_}
  11[041] - pop 1
  12[095] - unlink try 0
  14[020] - load literal -2
  16[015] - load local 1
- 17[062] - invoke eq // {True_|False_}
+ 17[062] - invoke eq // [{SmallInteger_}, {SmallInteger_}] -> {True_|False_}
  18[022] - load null
  19[015] - load local 1
  20[082] - branch if false T25
@@ -124,12 +124,12 @@ catchy tests/type_propagation/finally_test.toit
   0[029] - load [block] in catchy tests/type_propagation/finally_test.toit
   5[094] - link try 0
   7[038] - load block 4
-  9[055] - invoke block S1 // {}
+  9[055] - invoke block S1 // [[block]] -> {}
  11[041] - pop 1
  12[095] - unlink try 0
  14[020] - load literal -2
  16[015] - load local 1
- 17[062] - invoke eq // {True_|False_}
+ 17[062] - invoke eq // [{SmallInteger_}, {SmallInteger_}] -> {True_|False_}
  18[022] - load null
  19[015] - load local 1
  20[082] - branch if false T25
@@ -151,11 +151,11 @@ test_nlb_out_of_try tests/type_propagation/finally_test.toit
   2[029] - load [block] in test_nlb_out_of_try tests/type_propagation/finally_test.toit
   7[094] - link try 0
   9[038] - load block 4
- 11[055] - invoke block S1 // {Null_}
+ 11[055] - invoke block S1 // [[block]] -> {Null_}
  13[041] - pop 1
  14[095] - unlink try 0
  16[018] - load local 4
- 17[053] - invoke static id tests/type_propagation/finally_test.toit // {String_|Null_|SmallInteger_}
+ 17[053] - invoke static id tests/type_propagation/finally_test.toit // [{String_|Null_|SmallInteger_}] -> {String_|Null_|SmallInteger_}
  20[041] - pop 1
  21[096] - unwind
  22[089] - return null S2 0
@@ -164,7 +164,7 @@ test_nlb_out_of_try tests/type_propagation/finally_test.toit
  - argument 0: [block]
   0[029] - load [block] in [block] in test_nlb_out_of_try tests/type_propagation/finally_test.toit
   5[038] - load block 0
-  7[053] - invoke static invoke tests/type_propagation/finally_test.toit // {}
+  7[053] - invoke static invoke tests/type_propagation/finally_test.toit // [[block]] -> {}
  10[040] - pop 2
  12[083] - branch back T0
  17[016] - load local 2
@@ -175,7 +175,7 @@ test_nlb_out_of_try tests/type_propagation/finally_test.toit
  26[082] - branch if false T41
  29[029] - load [block] in [block] in test_nlb_out_of_try tests/type_propagation/finally_test.toit
  34[038] - load block 0
- 36[053] - invoke static invoke tests/type_propagation/finally_test.toit // {}
+ 36[053] - invoke static invoke tests/type_propagation/finally_test.toit // [[block]] -> {}
  39[040] - pop 2
  41[016] - load local 2
  42[022] - load null
@@ -203,13 +203,13 @@ id tests/type_propagation/finally_test.toit
 
 pick tests/type_propagation/finally_test.toit
   0[026] - load smi 100
-  2[053] - invoke static random <sdk>/core/utils.toit // {LargeInteger_|SmallInteger_}
+  2[053] - invoke static random <sdk>/core/utils.toit // [{SmallInteger_}] -> {LargeInteger_|SmallInteger_}
   5[026] - load smi 50
-  7[063] - invoke lt // {True_|False_}
+  7[063] - invoke lt // [{LargeInteger_|SmallInteger_}, {SmallInteger_}] -> {True_|False_}
   8[088] - return S1 0
 
 invoke tests/type_propagation/finally_test.toit
  - argument 0: [block]
   0[016] - load local 2
-  1[055] - invoke block S1 // {}
+  1[055] - invoke block S1 // [[block]] -> {}
   3[041] - pop 1
diff --git a/tests/type_propagation/gold/global_test.gold b/tests/type_propagation/gold/global_test.gold
index 26a7b220e..fb79fdd06 100644
--- a/tests/type_propagation/gold/global_test.gold
+++ b/tests/type_propagation/gold/global_test.gold
@@ -16,19 +16,19 @@ Z tests/type_propagation/global_test.toit
 
 test_simple tests/type_propagation/global_test.toit
   0[033] - load global var lazy G0 // {SmallInteger_}
-  2[053] - invoke static id tests/type_propagation/global_test.toit // {SmallInteger_}
+  2[053] - invoke static id tests/type_propagation/global_test.toit // [{SmallInteger_}] -> {SmallInteger_}
   5[041] - pop 1
   6[033] - load global var lazy G1 // {String_|SmallInteger_}
-  8[053] - invoke static id tests/type_propagation/global_test.toit // {String_|SmallInteger_}
+  8[053] - invoke static id tests/type_propagation/global_test.toit // [{String_|SmallInteger_}] -> {String_|SmallInteger_}
  11[041] - pop 1
  12[020] - load literal hest
  14[035] - store global var G1
  16[041] - pop 1
  17[033] - load global var lazy G1 // {String_|SmallInteger_}
- 19[053] - invoke static id tests/type_propagation/global_test.toit // {String_|SmallInteger_}
+ 19[053] - invoke static id tests/type_propagation/global_test.toit // [{String_|SmallInteger_}] -> {String_|SmallInteger_}
  22[041] - pop 1
  23[033] - load global var lazy G2 // {SmallInteger_}
- 25[053] - invoke static id tests/type_propagation/global_test.toit // {SmallInteger_}
+ 25[053] - invoke static id tests/type_propagation/global_test.toit // [{SmallInteger_}] -> {SmallInteger_}
  28[089] - return null S1 0
 
 foo tests/type_propagation/global_test.toit
diff --git a/tests/type_propagation/gold/global_test.gold-O2 b/tests/type_propagation/gold/global_test.gold-O2
index 26a7b220e..fb79fdd06 100644
--- a/tests/type_propagation/gold/global_test.gold-O2
+++ b/tests/type_propagation/gold/global_test.gold-O2
@@ -16,19 +16,19 @@ Z tests/type_propagation/global_test.toit
 
 test_simple tests/type_propagation/global_test.toit
   0[033] - load global var lazy G0 // {SmallInteger_}
-  2[053] - invoke static id tests/type_propagation/global_test.toit // {SmallInteger_}
+  2[053] - invoke static id tests/type_propagation/global_test.toit // [{SmallInteger_}] -> {SmallInteger_}
   5[041] - pop 1
   6[033] - load global var lazy G1 // {String_|SmallInteger_}
-  8[053] - invoke static id tests/type_propagation/global_test.toit // {String_|SmallInteger_}
+  8[053] - invoke static id tests/type_propagation/global_test.toit // [{String_|SmallInteger_}] -> {String_|SmallInteger_}
  11[041] - pop 1
  12[020] - load literal hest
  14[035] - store global var G1
  16[041] - pop 1
  17[033] - load global var lazy G1 // {String_|SmallInteger_}
- 19[053] - invoke static id tests/type_propagation/global_test.toit // {String_|SmallInteger_}
+ 19[053] - invoke static id tests/type_propagation/global_test.toit // [{String_|SmallInteger_}] -> {String_|SmallInteger_}
  22[041] - pop 1
  23[033] - load global var lazy G2 // {SmallInteger_}
- 25[053] - invoke static id tests/type_propagation/global_test.toit // {SmallInteger_}
+ 25[053] - invoke static id tests/type_propagation/global_test.toit // [{SmallInteger_}] -> {SmallInteger_}
  28[089] - return null S1 0
 
 foo tests/type_propagation/global_test.toit
diff --git a/tests/type_propagation/gold/lambda_test.gold b/tests/type_propagation/gold/lambda_test.gold
index 3bf2bb6b3..9a00a90e6 100644
--- a/tests/type_propagation/gold/lambda_test.gold
+++ b/tests/type_propagation/gold/lambda_test.gold
@@ -8,13 +8,13 @@ test_simple tests/type_propagation/lambda_test.toit
   0[029] - load [lambda] in test_simple tests/type_propagation/lambda_test.toit
   5[023] - load smi 0
   6[022] - load null
-  7[053] - invoke static Array_ <sdk>/core/collections.toit // {LargeArray_|SmallArray_}
+  7[053] - invoke static Array_ <sdk>/core/collections.toit // [{SmallInteger_}, {Null_}] -> {LargeArray_|SmallArray_}
  10[014] - load local 0
  11[004] - store local, pop S1
  13[023] - load smi 0
- 14[053] - invoke static lambda_ <sdk>/core/objects.toit // {Lambda}
+ 14[053] - invoke static lambda_ <sdk>/core/objects.toit // [{SmallInteger_}, {LargeArray_|SmallArray_}, {SmallInteger_}] -> {Lambda}
  17[014] - load local 0
- 18[053] - invoke static Lambda.call <sdk>/core/objects.toit // {*}
+ 18[053] - invoke static Lambda.call <sdk>/core/objects.toit // [{Lambda}] -> {*}
  21[088] - return S2 0
 
 [lambda] in test_simple tests/type_propagation/lambda_test.toit
@@ -25,40 +25,40 @@ test_arguments tests/type_propagation/lambda_test.toit
   0[029] - load [lambda] in test_arguments tests/type_propagation/lambda_test.toit
   5[023] - load smi 0
   6[022] - load null
-  7[053] - invoke static Array_ <sdk>/core/collections.toit // {LargeArray_|SmallArray_}
+  7[053] - invoke static Array_ <sdk>/core/collections.toit // [{SmallInteger_}, {Null_}] -> {LargeArray_|SmallArray_}
  10[014] - load local 0
  11[004] - store local, pop S1
  13[023] - load smi 0
- 14[053] - invoke static lambda_ <sdk>/core/objects.toit // {Lambda}
+ 14[053] - invoke static lambda_ <sdk>/core/objects.toit // [{SmallInteger_}, {LargeArray_|SmallArray_}, {SmallInteger_}] -> {Lambda}
  17[026] - load smi 42
- 19[053] - invoke static Lambda.call <sdk>/core/objects.toit // {*}
+ 19[053] - invoke static Lambda.call <sdk>/core/objects.toit // [{Lambda}, {SmallInteger_}] -> {*}
  22[041] - pop 1
  23[029] - load [lambda] in test_arguments tests/type_propagation/lambda_test.toit
  28[023] - load smi 0
  29[022] - load null
- 30[053] - invoke static Array_ <sdk>/core/collections.toit // {LargeArray_|SmallArray_}
+ 30[053] - invoke static Array_ <sdk>/core/collections.toit // [{SmallInteger_}, {Null_}] -> {LargeArray_|SmallArray_}
  33[014] - load local 0
  34[004] - store local, pop S1
  36[023] - load smi 0
- 37[053] - invoke static lambda_ <sdk>/core/objects.toit // {Lambda}
+ 37[053] - invoke static lambda_ <sdk>/core/objects.toit // [{SmallInteger_}, {LargeArray_|SmallArray_}, {SmallInteger_}] -> {Lambda}
  40[026] - load smi 42
  42[020] - load literal fisk
- 44[053] - invoke static Lambda.call <sdk>/core/objects.toit // {*}
+ 44[053] - invoke static Lambda.call <sdk>/core/objects.toit // [{Lambda}, {SmallInteger_}, {String_}] -> {*}
  47[089] - return null S1 0
 
 [lambda] in test_arguments tests/type_propagation/lambda_test.toit
  - argument 0: {*}
   0[016] - load local 2
-  1[053] - invoke static id tests/type_propagation/lambda_test.toit // {*}
+  1[053] - invoke static id tests/type_propagation/lambda_test.toit // [{*}] -> {*}
   4[088] - return S1 1
 
 [lambda] in test_arguments tests/type_propagation/lambda_test.toit
  - argument 0: {*}
  - argument 1: {*}
   0[017] - load local 3
-  1[053] - invoke static id tests/type_propagation/lambda_test.toit // {*}
+  1[053] - invoke static id tests/type_propagation/lambda_test.toit // [{*}] -> {*}
   4[002] - pop, load local S2
-  6[053] - invoke static id tests/type_propagation/lambda_test.toit // {*}
+  6[053] - invoke static id tests/type_propagation/lambda_test.toit // [{*}] -> {*}
   9[088] - return S1 2
 
 id tests/type_propagation/lambda_test.toit
diff --git a/tests/type_propagation/gold/lambda_test.gold-O2 b/tests/type_propagation/gold/lambda_test.gold-O2
index 3bf2bb6b3..9a00a90e6 100644
--- a/tests/type_propagation/gold/lambda_test.gold-O2
+++ b/tests/type_propagation/gold/lambda_test.gold-O2
@@ -8,13 +8,13 @@ test_simple tests/type_propagation/lambda_test.toit
   0[029] - load [lambda] in test_simple tests/type_propagation/lambda_test.toit
   5[023] - load smi 0
   6[022] - load null
-  7[053] - invoke static Array_ <sdk>/core/collections.toit // {LargeArray_|SmallArray_}
+  7[053] - invoke static Array_ <sdk>/core/collections.toit // [{SmallInteger_}, {Null_}] -> {LargeArray_|SmallArray_}
  10[014] - load local 0
  11[004] - store local, pop S1
  13[023] - load smi 0
- 14[053] - invoke static lambda_ <sdk>/core/objects.toit // {Lambda}
+ 14[053] - invoke static lambda_ <sdk>/core/objects.toit // [{SmallInteger_}, {LargeArray_|SmallArray_}, {SmallInteger_}] -> {Lambda}
  17[014] - load local 0
- 18[053] - invoke static Lambda.call <sdk>/core/objects.toit // {*}
+ 18[053] - invoke static Lambda.call <sdk>/core/objects.toit // [{Lambda}] -> {*}
  21[088] - return S2 0
 
 [lambda] in test_simple tests/type_propagation/lambda_test.toit
@@ -25,40 +25,40 @@ test_arguments tests/type_propagation/lambda_test.toit
   0[029] - load [lambda] in test_arguments tests/type_propagation/lambda_test.toit
   5[023] - load smi 0
   6[022] - load null
-  7[053] - invoke static Array_ <sdk>/core/collections.toit // {LargeArray_|SmallArray_}
+  7[053] - invoke static Array_ <sdk>/core/collections.toit // [{SmallInteger_}, {Null_}] -> {LargeArray_|SmallArray_}
  10[014] - load local 0
  11[004] - store local, pop S1
  13[023] - load smi 0
- 14[053] - invoke static lambda_ <sdk>/core/objects.toit // {Lambda}
+ 14[053] - invoke static lambda_ <sdk>/core/objects.toit // [{SmallInteger_}, {LargeArray_|SmallArray_}, {SmallInteger_}] -> {Lambda}
  17[026] - load smi 42
- 19[053] - invoke static Lambda.call <sdk>/core/objects.toit // {*}
+ 19[053] - invoke static Lambda.call <sdk>/core/objects.toit // [{Lambda}, {SmallInteger_}] -> {*}
  22[041] - pop 1
  23[029] - load [lambda] in test_arguments tests/type_propagation/lambda_test.toit
  28[023] - load smi 0
  29[022] - load null
- 30[053] - invoke static Array_ <sdk>/core/collections.toit // {LargeArray_|SmallArray_}
+ 30[053] - invoke static Array_ <sdk>/core/collections.toit // [{SmallInteger_}, {Null_}] -> {LargeArray_|SmallArray_}
  33[014] - load local 0
  34[004] - store local, pop S1
  36[023] - load smi 0
- 37[053] - invoke static lambda_ <sdk>/core/objects.toit // {Lambda}
+ 37[053] - invoke static lambda_ <sdk>/core/objects.toit // [{SmallInteger_}, {LargeArray_|SmallArray_}, {SmallInteger_}] -> {Lambda}
  40[026] - load smi 42
  42[020] - load literal fisk
- 44[053] - invoke static Lambda.call <sdk>/core/objects.toit // {*}
+ 44[053] - invoke static Lambda.call <sdk>/core/objects.toit // [{Lambda}, {SmallInteger_}, {String_}] -> {*}
  47[089] - return null S1 0
 
 [lambda] in test_arguments tests/type_propagation/lambda_test.toit
  - argument 0: {*}
   0[016] - load local 2
-  1[053] - invoke static id tests/type_propagation/lambda_test.toit // {*}
+  1[053] - invoke static id tests/type_propagation/lambda_test.toit // [{*}] -> {*}
   4[088] - return S1 1
 
 [lambda] in test_arguments tests/type_propagation/lambda_test.toit
  - argument 0: {*}
  - argument 1: {*}
   0[017] - load local 3
-  1[053] - invoke static id tests/type_propagation/lambda_test.toit // {*}
+  1[053] - invoke static id tests/type_propagation/lambda_test.toit // [{*}] -> {*}
   4[002] - pop, load local S2
-  6[053] - invoke static id tests/type_propagation/lambda_test.toit // {*}
+  6[053] - invoke static id tests/type_propagation/lambda_test.toit // [{*}] -> {*}
   9[088] - return S1 2
 
 id tests/type_propagation/lambda_test.toit
diff --git a/tests/type_propagation/gold/literal_test.gold b/tests/type_propagation/gold/literal_test.gold
index e9f2fc7bd..2a1dcff90 100644
--- a/tests/type_propagation/gold/literal_test.gold
+++ b/tests/type_propagation/gold/literal_test.gold
@@ -18,7 +18,7 @@ get_smi_or_string tests/type_propagation/literal_test.toit
   0[053] - invoke static get_smi tests/type_propagation/literal_test.toit // {SmallInteger_}
   3[014] - load local 0
   4[023] - load smi 0
-  5[062] - invoke eq // {True_|False_}
+  5[062] - invoke eq // [{SmallInteger_}, {SmallInteger_}] -> {True_|False_}
   6[082] - branch if false T13
   9[014] - load local 0
  10[088] - return S2 0
diff --git a/tests/type_propagation/gold/literal_test.gold-O2 b/tests/type_propagation/gold/literal_test.gold-O2
index e9f2fc7bd..2a1dcff90 100644
--- a/tests/type_propagation/gold/literal_test.gold-O2
+++ b/tests/type_propagation/gold/literal_test.gold-O2
@@ -18,7 +18,7 @@ get_smi_or_string tests/type_propagation/literal_test.toit
   0[053] - invoke static get_smi tests/type_propagation/literal_test.toit // {SmallInteger_}
   3[014] - load local 0
   4[023] - load smi 0
-  5[062] - invoke eq // {True_|False_}
+  5[062] - invoke eq // [{SmallInteger_}, {SmallInteger_}] -> {True_|False_}
   6[082] - branch if false T13
   9[014] - load local 0
  10[088] - return S2 0
diff --git a/tests/type_propagation/gold/local_test.gold b/tests/type_propagation/gold/local_test.gold
index 14f2824f7..c46be7ff1 100644
--- a/tests/type_propagation/gold/local_test.gold
+++ b/tests/type_propagation/gold/local_test.gold
@@ -21,12 +21,12 @@ test_if tests/type_propagation/local_test.toit
   7[020] - load literal horse
   9[004] - store local, pop S1
  11[014] - load local 0
- 12[053] - invoke static id tests/type_propagation/local_test.toit // {String_|SmallInteger_}
+ 12[053] - invoke static id tests/type_propagation/local_test.toit // [{String_|SmallInteger_}] -> {String_|SmallInteger_}
  15[041] - pop 1
  16[026] - load smi 42
  18[004] - store local, pop S1
  20[014] - load local 0
- 21[053] - invoke static id tests/type_propagation/local_test.toit // {SmallInteger_}
+ 21[053] - invoke static id tests/type_propagation/local_test.toit // [{SmallInteger_}] -> {SmallInteger_}
  24[089] - return null S2 0
 
 test_if_else tests/type_propagation/local_test.toit
@@ -36,7 +36,7 @@ test_if_else tests/type_propagation/local_test.toit
   7[020] - load literal horse
   9[004] - store local, pop S1
  11[014] - load local 0
- 12[053] - invoke static id tests/type_propagation/local_test.toit // {String_|SmallInteger_}
+ 12[053] - invoke static id tests/type_propagation/local_test.toit // [{String_|SmallInteger_}] -> {String_|SmallInteger_}
  15[041] - pop 1
  16[053] - invoke static pick tests/type_propagation/local_test.toit // {True_|False_}
  19[082] - branch if false T29
@@ -46,7 +46,7 @@ test_if_else tests/type_propagation/local_test.toit
  29[020] - load literal true
  31[004] - store local, pop S1
  33[014] - load local 0
- 34[053] - invoke static id tests/type_propagation/local_test.toit // {String_|True_}
+ 34[053] - invoke static id tests/type_propagation/local_test.toit // [{String_|True_}] -> {String_|True_}
  37[089] - return null S2 0
 
 test_if_nested tests/type_propagation/local_test.toit
@@ -61,7 +61,7 @@ test_if_nested tests/type_propagation/local_test.toit
  20[020] - load literal 3.1000000000000000888
  22[004] - store local, pop S1
  24[014] - load local 0
- 25[053] - invoke static id tests/type_propagation/local_test.toit // {float|SmallInteger_}
+ 25[053] - invoke static id tests/type_propagation/local_test.toit // [{float|SmallInteger_}] -> {float|SmallInteger_}
  28[041] - pop 1
  29[080] - branch T54
  32[053] - invoke static pick tests/type_propagation/local_test.toit // {True_|False_}
@@ -72,10 +72,10 @@ test_if_nested tests/type_propagation/local_test.toit
  45[020] - load literal false
  47[004] - store local, pop S1
  49[014] - load local 0
- 50[053] - invoke static id tests/type_propagation/local_test.toit // {True_|False_}
+ 50[053] - invoke static id tests/type_propagation/local_test.toit // [{True_|False_}] -> {True_|False_}
  53[041] - pop 1
  54[014] - load local 0
- 55[053] - invoke static id tests/type_propagation/local_test.toit // {True_|False_|float|SmallInteger_}
+ 55[053] - invoke static id tests/type_propagation/local_test.toit // [{True_|False_|float|SmallInteger_}] -> {True_|False_|float|SmallInteger_}
  58[089] - return null S2 0
 
 test_if_more_locals tests/type_propagation/local_test.toit
@@ -88,26 +88,26 @@ test_if_more_locals tests/type_propagation/local_test.toit
  12[026] - load smi 87
  14[004] - store local, pop S1
  16[017] - load local 3
- 17[053] - invoke static id tests/type_propagation/local_test.toit // {SmallInteger_}
+ 17[053] - invoke static id tests/type_propagation/local_test.toit // [{SmallInteger_}] -> {SmallInteger_}
  20[002] - pop, load local S2
- 22[053] - invoke static id tests/type_propagation/local_test.toit // {True_}
+ 22[053] - invoke static id tests/type_propagation/local_test.toit // [{True_}] -> {True_}
  25[002] - pop, load local S1
- 27[053] - invoke static id tests/type_propagation/local_test.toit // {float}
+ 27[053] - invoke static id tests/type_propagation/local_test.toit // [{float}] -> {float}
  30[002] - pop, load local S0
- 32[053] - invoke static id tests/type_propagation/local_test.toit // {Null_|SmallInteger_}
+ 32[053] - invoke static id tests/type_propagation/local_test.toit // [{Null_|SmallInteger_}] -> {Null_|SmallInteger_}
  35[041] - pop 1
  36[053] - invoke static pick tests/type_propagation/local_test.toit // {True_|False_}
  39[082] - branch if false T46
  42[020] - load literal false
  44[004] - store local, pop S3
  46[017] - load local 3
- 47[053] - invoke static id tests/type_propagation/local_test.toit // {SmallInteger_}
+ 47[053] - invoke static id tests/type_propagation/local_test.toit // [{SmallInteger_}] -> {SmallInteger_}
  50[002] - pop, load local S2
- 52[053] - invoke static id tests/type_propagation/local_test.toit // {True_|False_}
+ 52[053] - invoke static id tests/type_propagation/local_test.toit // [{True_|False_}] -> {True_|False_}
  55[002] - pop, load local S1
- 57[053] - invoke static id tests/type_propagation/local_test.toit // {float}
+ 57[053] - invoke static id tests/type_propagation/local_test.toit // [{float}] -> {float}
  60[002] - pop, load local S0
- 62[053] - invoke static id tests/type_propagation/local_test.toit // {Null_|SmallInteger_}
+ 62[053] - invoke static id tests/type_propagation/local_test.toit // [{Null_|SmallInteger_}] -> {Null_|SmallInteger_}
  65[089] - return null S5 0
 
 test_loop_simple tests/type_propagation/local_test.toit
@@ -117,11 +117,11 @@ test_loop_simple tests/type_propagation/local_test.toit
   7[026] - load smi 2
   9[004] - store local, pop S1
  11[014] - load local 0
- 12[053] - invoke static id tests/type_propagation/local_test.toit // {SmallInteger_}
+ 12[053] - invoke static id tests/type_propagation/local_test.toit // [{SmallInteger_}] -> {SmallInteger_}
  15[041] - pop 1
  16[083] - branch back T1
  21[014] - load local 0
- 22[053] - invoke static id tests/type_propagation/local_test.toit // {Null_|SmallInteger_}
+ 22[053] - invoke static id tests/type_propagation/local_test.toit // [{Null_|SmallInteger_}] -> {Null_|SmallInteger_}
  25[089] - return null S2 0
 
 test_loop_break tests/type_propagation/local_test.toit
@@ -133,7 +133,7 @@ test_loop_break tests/type_propagation/local_test.toit
  11[080] - branch T19
  14[083] - branch back T1
  19[014] - load local 0
- 20[053] - invoke static id tests/type_propagation/local_test.toit // {SmallInteger_}
+ 20[053] - invoke static id tests/type_propagation/local_test.toit // [{SmallInteger_}] -> {SmallInteger_}
  23[041] - pop 1
  24[022] - load null
  25[020] - load literal horse
@@ -146,13 +146,13 @@ test_loop_break tests/type_propagation/local_test.toit
  44[026] - load smi 42
  46[004] - store local, pop S1
  48[014] - load local 0
- 49[053] - invoke static id tests/type_propagation/local_test.toit // {String_|SmallInteger_}
+ 49[053] - invoke static id tests/type_propagation/local_test.toit // [{String_|SmallInteger_}] -> {String_|SmallInteger_}
  52[041] - pop 1
  53[083] - branch back T25
  58[015] - load local 1
- 59[053] - invoke static id tests/type_propagation/local_test.toit // {SmallInteger_}
+ 59[053] - invoke static id tests/type_propagation/local_test.toit // [{SmallInteger_}] -> {SmallInteger_}
  62[002] - pop, load local S0
- 64[053] - invoke static id tests/type_propagation/local_test.toit // {String_}
+ 64[053] - invoke static id tests/type_propagation/local_test.toit // [{String_}] -> {String_}
  67[089] - return null S3 0
 
 test_loop_continue tests/type_propagation/local_test.toit
@@ -164,7 +164,7 @@ test_loop_continue tests/type_propagation/local_test.toit
  11[080] - branch T14
  14[083] - branch back T1
  19[014] - load local 0
- 20[053] - invoke static id tests/type_propagation/local_test.toit // {Null_|SmallInteger_}
+ 20[053] - invoke static id tests/type_propagation/local_test.toit // [{Null_|SmallInteger_}] -> {Null_|SmallInteger_}
  23[041] - pop 1
  24[022] - load null
  25[053] - invoke static pick tests/type_propagation/local_test.toit // {True_|False_}
@@ -179,9 +179,9 @@ test_loop_continue tests/type_propagation/local_test.toit
  49[004] - store local, pop S1
  51[083] - branch back T25
  56[015] - load local 1
- 57[053] - invoke static id tests/type_propagation/local_test.toit // {Null_|SmallInteger_}
+ 57[053] - invoke static id tests/type_propagation/local_test.toit // [{Null_|SmallInteger_}] -> {Null_|SmallInteger_}
  60[002] - pop, load local S0
- 62[053] - invoke static id tests/type_propagation/local_test.toit // {String_|Null_|SmallInteger_}
+ 62[053] - invoke static id tests/type_propagation/local_test.toit // [{String_|Null_|SmallInteger_}] -> {String_|Null_|SmallInteger_}
  65[089] - return null S3 0
 
 id tests/type_propagation/local_test.toit
@@ -191,7 +191,7 @@ id tests/type_propagation/local_test.toit
 
 pick tests/type_propagation/local_test.toit
   0[026] - load smi 100
-  2[053] - invoke static random <sdk>/core/utils.toit // {LargeInteger_|SmallInteger_}
+  2[053] - invoke static random <sdk>/core/utils.toit // [{SmallInteger_}] -> {LargeInteger_|SmallInteger_}
   5[026] - load smi 50
-  7[063] - invoke lt // {True_|False_}
+  7[063] - invoke lt // [{LargeInteger_|SmallInteger_}, {SmallInteger_}] -> {True_|False_}
   8[088] - return S1 0
diff --git a/tests/type_propagation/gold/local_test.gold-O2 b/tests/type_propagation/gold/local_test.gold-O2
index 14f2824f7..c46be7ff1 100644
--- a/tests/type_propagation/gold/local_test.gold-O2
+++ b/tests/type_propagation/gold/local_test.gold-O2
@@ -21,12 +21,12 @@ test_if tests/type_propagation/local_test.toit
   7[020] - load literal horse
   9[004] - store local, pop S1
  11[014] - load local 0
- 12[053] - invoke static id tests/type_propagation/local_test.toit // {String_|SmallInteger_}
+ 12[053] - invoke static id tests/type_propagation/local_test.toit // [{String_|SmallInteger_}] -> {String_|SmallInteger_}
  15[041] - pop 1
  16[026] - load smi 42
  18[004] - store local, pop S1
  20[014] - load local 0
- 21[053] - invoke static id tests/type_propagation/local_test.toit // {SmallInteger_}
+ 21[053] - invoke static id tests/type_propagation/local_test.toit // [{SmallInteger_}] -> {SmallInteger_}
  24[089] - return null S2 0
 
 test_if_else tests/type_propagation/local_test.toit
@@ -36,7 +36,7 @@ test_if_else tests/type_propagation/local_test.toit
   7[020] - load literal horse
   9[004] - store local, pop S1
  11[014] - load local 0
- 12[053] - invoke static id tests/type_propagation/local_test.toit // {String_|SmallInteger_}
+ 12[053] - invoke static id tests/type_propagation/local_test.toit // [{String_|SmallInteger_}] -> {String_|SmallInteger_}
  15[041] - pop 1
  16[053] - invoke static pick tests/type_propagation/local_test.toit // {True_|False_}
  19[082] - branch if false T29
@@ -46,7 +46,7 @@ test_if_else tests/type_propagation/local_test.toit
  29[020] - load literal true
  31[004] - store local, pop S1
  33[014] - load local 0
- 34[053] - invoke static id tests/type_propagation/local_test.toit // {String_|True_}
+ 34[053] - invoke static id tests/type_propagation/local_test.toit // [{String_|True_}] -> {String_|True_}
  37[089] - return null S2 0
 
 test_if_nested tests/type_propagation/local_test.toit
@@ -61,7 +61,7 @@ test_if_nested tests/type_propagation/local_test.toit
  20[020] - load literal 3.1000000000000000888
  22[004] - store local, pop S1
  24[014] - load local 0
- 25[053] - invoke static id tests/type_propagation/local_test.toit // {float|SmallInteger_}
+ 25[053] - invoke static id tests/type_propagation/local_test.toit // [{float|SmallInteger_}] -> {float|SmallInteger_}
  28[041] - pop 1
  29[080] - branch T54
  32[053] - invoke static pick tests/type_propagation/local_test.toit // {True_|False_}
@@ -72,10 +72,10 @@ test_if_nested tests/type_propagation/local_test.toit
  45[020] - load literal false
  47[004] - store local, pop S1
  49[014] - load local 0
- 50[053] - invoke static id tests/type_propagation/local_test.toit // {True_|False_}
+ 50[053] - invoke static id tests/type_propagation/local_test.toit // [{True_|False_}] -> {True_|False_}
  53[041] - pop 1
  54[014] - load local 0
- 55[053] - invoke static id tests/type_propagation/local_test.toit // {True_|False_|float|SmallInteger_}
+ 55[053] - invoke static id tests/type_propagation/local_test.toit // [{True_|False_|float|SmallInteger_}] -> {True_|False_|float|SmallInteger_}
  58[089] - return null S2 0
 
 test_if_more_locals tests/type_propagation/local_test.toit
@@ -88,26 +88,26 @@ test_if_more_locals tests/type_propagation/local_test.toit
  12[026] - load smi 87
  14[004] - store local, pop S1
  16[017] - load local 3
- 17[053] - invoke static id tests/type_propagation/local_test.toit // {SmallInteger_}
+ 17[053] - invoke static id tests/type_propagation/local_test.toit // [{SmallInteger_}] -> {SmallInteger_}
  20[002] - pop, load local S2
- 22[053] - invoke static id tests/type_propagation/local_test.toit // {True_}
+ 22[053] - invoke static id tests/type_propagation/local_test.toit // [{True_}] -> {True_}
  25[002] - pop, load local S1
- 27[053] - invoke static id tests/type_propagation/local_test.toit // {float}
+ 27[053] - invoke static id tests/type_propagation/local_test.toit // [{float}] -> {float}
  30[002] - pop, load local S0
- 32[053] - invoke static id tests/type_propagation/local_test.toit // {Null_|SmallInteger_}
+ 32[053] - invoke static id tests/type_propagation/local_test.toit // [{Null_|SmallInteger_}] -> {Null_|SmallInteger_}
  35[041] - pop 1
  36[053] - invoke static pick tests/type_propagation/local_test.toit // {True_|False_}
  39[082] - branch if false T46
  42[020] - load literal false
  44[004] - store local, pop S3
  46[017] - load local 3
- 47[053] - invoke static id tests/type_propagation/local_test.toit // {SmallInteger_}
+ 47[053] - invoke static id tests/type_propagation/local_test.toit // [{SmallInteger_}] -> {SmallInteger_}
  50[002] - pop, load local S2
- 52[053] - invoke static id tests/type_propagation/local_test.toit // {True_|False_}
+ 52[053] - invoke static id tests/type_propagation/local_test.toit // [{True_|False_}] -> {True_|False_}
  55[002] - pop, load local S1
- 57[053] - invoke static id tests/type_propagation/local_test.toit // {float}
+ 57[053] - invoke static id tests/type_propagation/local_test.toit // [{float}] -> {float}
  60[002] - pop, load local S0
- 62[053] - invoke static id tests/type_propagation/local_test.toit // {Null_|SmallInteger_}
+ 62[053] - invoke static id tests/type_propagation/local_test.toit // [{Null_|SmallInteger_}] -> {Null_|SmallInteger_}
  65[089] - return null S5 0
 
 test_loop_simple tests/type_propagation/local_test.toit
@@ -117,11 +117,11 @@ test_loop_simple tests/type_propagation/local_test.toit
   7[026] - load smi 2
   9[004] - store local, pop S1
  11[014] - load local 0
- 12[053] - invoke static id tests/type_propagation/local_test.toit // {SmallInteger_}
+ 12[053] - invoke static id tests/type_propagation/local_test.toit // [{SmallInteger_}] -> {SmallInteger_}
  15[041] - pop 1
  16[083] - branch back T1
  21[014] - load local 0
- 22[053] - invoke static id tests/type_propagation/local_test.toit // {Null_|SmallInteger_}
+ 22[053] - invoke static id tests/type_propagation/local_test.toit // [{Null_|SmallInteger_}] -> {Null_|SmallInteger_}
  25[089] - return null S2 0
 
 test_loop_break tests/type_propagation/local_test.toit
@@ -133,7 +133,7 @@ test_loop_break tests/type_propagation/local_test.toit
  11[080] - branch T19
  14[083] - branch back T1
  19[014] - load local 0
- 20[053] - invoke static id tests/type_propagation/local_test.toit // {SmallInteger_}
+ 20[053] - invoke static id tests/type_propagation/local_test.toit // [{SmallInteger_}] -> {SmallInteger_}
  23[041] - pop 1
  24[022] - load null
  25[020] - load literal horse
@@ -146,13 +146,13 @@ test_loop_break tests/type_propagation/local_test.toit
  44[026] - load smi 42
  46[004] - store local, pop S1
  48[014] - load local 0
- 49[053] - invoke static id tests/type_propagation/local_test.toit // {String_|SmallInteger_}
+ 49[053] - invoke static id tests/type_propagation/local_test.toit // [{String_|SmallInteger_}] -> {String_|SmallInteger_}
  52[041] - pop 1
  53[083] - branch back T25
  58[015] - load local 1
- 59[053] - invoke static id tests/type_propagation/local_test.toit // {SmallInteger_}
+ 59[053] - invoke static id tests/type_propagation/local_test.toit // [{SmallInteger_}] -> {SmallInteger_}
  62[002] - pop, load local S0
- 64[053] - invoke static id tests/type_propagation/local_test.toit // {String_}
+ 64[053] - invoke static id tests/type_propagation/local_test.toit // [{String_}] -> {String_}
  67[089] - return null S3 0
 
 test_loop_continue tests/type_propagation/local_test.toit
@@ -164,7 +164,7 @@ test_loop_continue tests/type_propagation/local_test.toit
  11[080] - branch T14
  14[083] - branch back T1
  19[014] - load local 0
- 20[053] - invoke static id tests/type_propagation/local_test.toit // {Null_|SmallInteger_}
+ 20[053] - invoke static id tests/type_propagation/local_test.toit // [{Null_|SmallInteger_}] -> {Null_|SmallInteger_}
  23[041] - pop 1
  24[022] - load null
  25[053] - invoke static pick tests/type_propagation/local_test.toit // {True_|False_}
@@ -179,9 +179,9 @@ test_loop_continue tests/type_propagation/local_test.toit
  49[004] - store local, pop S1
  51[083] - branch back T25
  56[015] - load local 1
- 57[053] - invoke static id tests/type_propagation/local_test.toit // {Null_|SmallInteger_}
+ 57[053] - invoke static id tests/type_propagation/local_test.toit // [{Null_|SmallInteger_}] -> {Null_|SmallInteger_}
  60[002] - pop, load local S0
- 62[053] - invoke static id tests/type_propagation/local_test.toit // {String_|Null_|SmallInteger_}
+ 62[053] - invoke static id tests/type_propagation/local_test.toit // [{String_|Null_|SmallInteger_}] -> {String_|Null_|SmallInteger_}
  65[089] - return null S3 0
 
 id tests/type_propagation/local_test.toit
@@ -191,7 +191,7 @@ id tests/type_propagation/local_test.toit
 
 pick tests/type_propagation/local_test.toit
   0[026] - load smi 100
-  2[053] - invoke static random <sdk>/core/utils.toit // {LargeInteger_|SmallInteger_}
+  2[053] - invoke static random <sdk>/core/utils.toit // [{SmallInteger_}] -> {LargeInteger_|SmallInteger_}
   5[026] - load smi 50
-  7[063] - invoke lt // {True_|False_}
+  7[063] - invoke lt // [{LargeInteger_|SmallInteger_}, {SmallInteger_}] -> {True_|False_}
   8[088] - return S1 0
diff --git a/tests/type_propagation/gold/map_test.gold b/tests/type_propagation/gold/map_test.gold
index 38e24caf9..68e59a96c 100644
--- a/tests/type_propagation/gold/map_test.gold
+++ b/tests/type_propagation/gold/map_test.gold
@@ -4,11 +4,11 @@ main tests/type_propagation/map_test.toit
 
 test_simple tests/type_propagation/map_test.toit
   0[042] - allocate instance Map
-  2[053] - invoke static Map <sdk>/core/collections.toit // {Map}
+  2[053] - invoke static Map <sdk>/core/collections.toit // [{Map}] -> {Map}
   5[014] - load local 0
   6[004] - store local, pop S1
-  8[009] - load field local 48 // {Null_|List_|SmallArray_}
- 10[053] - invoke static id tests/type_propagation/map_test.toit // {Null_|List_|SmallArray_}
+  8[009] - load field local 48 // [{Map}] -> {Null_|List_|SmallArray_}
+ 10[053] - invoke static id tests/type_propagation/map_test.toit // [{Null_|List_|SmallArray_}] -> {Null_|List_|SmallArray_}
  13[089] - return null S2 0
 
 id tests/type_propagation/map_test.toit
diff --git a/tests/type_propagation/gold/map_test.gold-O2 b/tests/type_propagation/gold/map_test.gold-O2
index 38e24caf9..68e59a96c 100644
--- a/tests/type_propagation/gold/map_test.gold-O2
+++ b/tests/type_propagation/gold/map_test.gold-O2
@@ -4,11 +4,11 @@ main tests/type_propagation/map_test.toit
 
 test_simple tests/type_propagation/map_test.toit
   0[042] - allocate instance Map
-  2[053] - invoke static Map <sdk>/core/collections.toit // {Map}
+  2[053] - invoke static Map <sdk>/core/collections.toit // [{Map}] -> {Map}
   5[014] - load local 0
   6[004] - store local, pop S1
-  8[009] - load field local 48 // {Null_|List_|SmallArray_}
- 10[053] - invoke static id tests/type_propagation/map_test.toit // {Null_|List_|SmallArray_}
+  8[009] - load field local 48 // [{Map}] -> {Null_|List_|SmallArray_}
+ 10[053] - invoke static id tests/type_propagation/map_test.toit // [{Null_|List_|SmallArray_}] -> {Null_|List_|SmallArray_}
  13[089] - return null S2 0
 
 id tests/type_propagation/map_test.toit
diff --git a/tests/type_propagation/gold/nlr_test.gold b/tests/type_propagation/gold/nlr_test.gold
index aa267d434..388cbf003 100644
--- a/tests/type_propagation/gold/nlr_test.gold
+++ b/tests/type_propagation/gold/nlr_test.gold
@@ -19,7 +19,7 @@ test_try tests/type_propagation/nlr_test.toit
 always_return tests/type_propagation/nlr_test.toit
   0[029] - load [block] in always_return tests/type_propagation/nlr_test.toit
   5[038] - load block 0
-  7[053] - invoke static invoke tests/type_propagation/nlr_test.toit // {}
+  7[053] - invoke static invoke tests/type_propagation/nlr_test.toit // [[block]] -> {}
  10[040] - pop 2
  12[053] - invoke static unreachable <sdk>/core/exceptions.toit
  15[041] - pop 1
@@ -34,7 +34,7 @@ always_return tests/type_propagation/nlr_test.toit
 maybe_return tests/type_propagation/nlr_test.toit
   0[029] - load [block] in maybe_return tests/type_propagation/nlr_test.toit
   5[038] - load block 0
-  7[053] - invoke static invoke tests/type_propagation/nlr_test.toit // {Null_}
+  7[053] - invoke static invoke tests/type_propagation/nlr_test.toit // [[block]] -> {Null_}
  10[040] - pop 2
  12[020] - load literal hest
  14[088] - return S1 0
@@ -55,7 +55,7 @@ stop_unwinding tests/type_propagation/nlr_test.toit
   2[029] - load [block] in stop_unwinding tests/type_propagation/nlr_test.toit
   7[094] - link try 0
   9[038] - load block 4
- 11[055] - invoke block S1 // {}
+ 11[055] - invoke block S1 // [[block]] -> {}
  13[041] - pop 1
  14[095] - unlink try 0
  16[018] - load local 4
@@ -74,7 +74,7 @@ stop_unwinding tests/type_propagation/nlr_test.toit
  10[041] - pop 1
  11[029] - load [block] in [block] in stop_unwinding tests/type_propagation/nlr_test.toit
  16[038] - load block 0
- 18[053] - invoke static invoke tests/type_propagation/nlr_test.toit // {}
+ 18[053] - invoke static invoke tests/type_propagation/nlr_test.toit // [[block]] -> {}
  21[041] - pop 1
  22[002] - pop, load local S2
  24[020] - load literal true
@@ -94,7 +94,7 @@ stop_unwinding_alternative tests/type_propagation/nlr_test.toit
   2[029] - load [block] in stop_unwinding_alternative tests/type_propagation/nlr_test.toit
   7[094] - link try 0
   9[038] - load block 4
- 11[055] - invoke block S1 // {True_}
+ 11[055] - invoke block S1 // [[block]] -> {True_}
  13[041] - pop 1
  14[095] - unlink try 0
  16[018] - load local 4
@@ -110,7 +110,7 @@ stop_unwinding_alternative tests/type_propagation/nlr_test.toit
   5[041] - pop 1
   6[029] - load [block] in [block] in stop_unwinding_alternative tests/type_propagation/nlr_test.toit
  11[038] - load block 0
- 13[053] - invoke static invoke tests/type_propagation/nlr_test.toit // {Null_}
+ 13[053] - invoke static invoke tests/type_propagation/nlr_test.toit // [[block]] -> {Null_}
  16[041] - pop 1
  17[002] - pop, load local S2
  19[020] - load literal true
@@ -131,13 +131,13 @@ stop_unwinding_alternative tests/type_propagation/nlr_test.toit
 
 pick tests/type_propagation/nlr_test.toit
   0[026] - load smi 100
-  2[053] - invoke static random <sdk>/core/utils.toit // {LargeInteger_|SmallInteger_}
+  2[053] - invoke static random <sdk>/core/utils.toit // [{SmallInteger_}] -> {LargeInteger_|SmallInteger_}
   5[026] - load smi 50
-  7[063] - invoke lt // {True_|False_}
+  7[063] - invoke lt // [{LargeInteger_|SmallInteger_}, {SmallInteger_}] -> {True_|False_}
   8[088] - return S1 0
 
 invoke tests/type_propagation/nlr_test.toit
  - argument 0: [block]
   0[016] - load local 2
-  1[055] - invoke block S1 // {Null_}
+  1[055] - invoke block S1 // [[block]] -> {Null_}
   3[088] - return S1 1
diff --git a/tests/type_propagation/gold/nlr_test.gold-O2 b/tests/type_propagation/gold/nlr_test.gold-O2
index 9d1415117..6ab4775ed 100644
--- a/tests/type_propagation/gold/nlr_test.gold-O2
+++ b/tests/type_propagation/gold/nlr_test.gold-O2
@@ -19,7 +19,7 @@ test_try tests/type_propagation/nlr_test.toit
 always_return tests/type_propagation/nlr_test.toit
   0[029] - load [block] in always_return tests/type_propagation/nlr_test.toit
   5[038] - load block 0
-  7[053] - invoke static invoke tests/type_propagation/nlr_test.toit // {}
+  7[053] - invoke static invoke tests/type_propagation/nlr_test.toit // [[block]] -> {}
  10[041] - pop 1
 
 [block] in always_return tests/type_propagation/nlr_test.toit
@@ -32,7 +32,7 @@ always_return tests/type_propagation/nlr_test.toit
 maybe_return tests/type_propagation/nlr_test.toit
   0[029] - load [block] in maybe_return tests/type_propagation/nlr_test.toit
   5[038] - load block 0
-  7[053] - invoke static invoke tests/type_propagation/nlr_test.toit // {Null_}
+  7[053] - invoke static invoke tests/type_propagation/nlr_test.toit // [[block]] -> {Null_}
  10[040] - pop 2
  12[020] - load literal hest
  14[088] - return S1 0
@@ -53,7 +53,7 @@ stop_unwinding tests/type_propagation/nlr_test.toit
   2[029] - load [block] in stop_unwinding tests/type_propagation/nlr_test.toit
   7[094] - link try 0
   9[038] - load block 4
- 11[055] - invoke block S1 // {}
+ 11[055] - invoke block S1 // [[block]] -> {}
  13[041] - pop 1
  14[095] - unlink try 0
  16[018] - load local 4
@@ -72,7 +72,7 @@ stop_unwinding tests/type_propagation/nlr_test.toit
  10[041] - pop 1
  11[029] - load [block] in [block] in stop_unwinding tests/type_propagation/nlr_test.toit
  16[038] - load block 0
- 18[053] - invoke static invoke tests/type_propagation/nlr_test.toit // {}
+ 18[053] - invoke static invoke tests/type_propagation/nlr_test.toit // [[block]] -> {}
  21[004] - store local, pop S1
  23[088] - return S1 1
 
@@ -89,7 +89,7 @@ stop_unwinding_alternative tests/type_propagation/nlr_test.toit
   2[029] - load [block] in stop_unwinding_alternative tests/type_propagation/nlr_test.toit
   7[094] - link try 0
   9[038] - load block 4
- 11[055] - invoke block S1 // {True_}
+ 11[055] - invoke block S1 // [[block]] -> {True_}
  13[041] - pop 1
  14[095] - unlink try 0
  16[018] - load local 4
@@ -105,7 +105,7 @@ stop_unwinding_alternative tests/type_propagation/nlr_test.toit
   5[041] - pop 1
   6[029] - load [block] in [block] in stop_unwinding_alternative tests/type_propagation/nlr_test.toit
  11[038] - load block 0
- 13[053] - invoke static invoke tests/type_propagation/nlr_test.toit // {Null_}
+ 13[053] - invoke static invoke tests/type_propagation/nlr_test.toit // [[block]] -> {Null_}
  16[041] - pop 1
  17[002] - pop, load local S2
  19[020] - load literal true
@@ -126,13 +126,13 @@ stop_unwinding_alternative tests/type_propagation/nlr_test.toit
 
 pick tests/type_propagation/nlr_test.toit
   0[026] - load smi 100
-  2[053] - invoke static random <sdk>/core/utils.toit // {LargeInteger_|SmallInteger_}
+  2[053] - invoke static random <sdk>/core/utils.toit // [{SmallInteger_}] -> {LargeInteger_|SmallInteger_}
   5[026] - load smi 50
-  7[063] - invoke lt // {True_|False_}
+  7[063] - invoke lt // [{LargeInteger_|SmallInteger_}, {SmallInteger_}] -> {True_|False_}
   8[088] - return S1 0
 
 invoke tests/type_propagation/nlr_test.toit
  - argument 0: [block]
   0[016] - load local 2
-  1[055] - invoke block S1 // {Null_}
+  1[055] - invoke block S1 // [[block]] -> {Null_}
   3[088] - return S1 1
diff --git a/tests/type_propagation/gold/non_local_branch_test.gold b/tests/type_propagation/gold/non_local_branch_test.gold
index 3d3f0ed99..1bd1ee53e 100644
--- a/tests/type_propagation/gold/non_local_branch_test.gold
+++ b/tests/type_propagation/gold/non_local_branch_test.gold
@@ -10,11 +10,11 @@ test_break tests/type_propagation/non_local_branch_test.toit
   0[026] - load smi 42
   2[029] - load [block] in test_break tests/type_propagation/non_local_branch_test.toit
   7[038] - load block 0
-  9[053] - invoke static invoke tests/type_propagation/non_local_branch_test.toit // {}
+  9[053] - invoke static invoke tests/type_propagation/non_local_branch_test.toit // [[block]] -> {}
  12[040] - pop 2
  14[083] - branch back T2
  19[014] - load local 0
- 20[053] - invoke static id tests/type_propagation/non_local_branch_test.toit // {String_}
+ 20[053] - invoke static id tests/type_propagation/non_local_branch_test.toit // [{String_}] -> {String_}
  23[089] - return null S2 0
 
 [block] in test_break tests/type_propagation/non_local_branch_test.toit
@@ -30,11 +30,11 @@ test_continue tests/type_propagation/non_local_branch_test.toit
   0[026] - load smi 42
   2[029] - load [block] in test_continue tests/type_propagation/non_local_branch_test.toit
   7[038] - load block 0
-  9[053] - invoke static invoke tests/type_propagation/non_local_branch_test.toit // {}
+  9[053] - invoke static invoke tests/type_propagation/non_local_branch_test.toit // [[block]] -> {}
  12[040] - pop 2
  14[083] - branch back T2
  19[014] - load local 0
- 20[053] - invoke static id tests/type_propagation/non_local_branch_test.toit // {float}
+ 20[053] - invoke static id tests/type_propagation/non_local_branch_test.toit // [{float}] -> {float}
  23[089] - return null S2 0
 
 [block] in test_continue tests/type_propagation/non_local_branch_test.toit
@@ -57,14 +57,14 @@ test_continue tests/type_propagation/non_local_branch_test.toit
 test_nested tests/type_propagation/non_local_branch_test.toit
   0[029] - load [block] in test_nested tests/type_propagation/non_local_branch_test.toit
   5[038] - load block 0
-  7[053] - invoke static invoke tests/type_propagation/non_local_branch_test.toit // {Null_}
+  7[053] - invoke static invoke tests/type_propagation/non_local_branch_test.toit // [[block]] -> {Null_}
  10[089] - return null S2 0
 
 [block] in test_nested tests/type_propagation/non_local_branch_test.toit
  - argument 0: [block]
   0[029] - load [block] in [block] in test_nested tests/type_propagation/non_local_branch_test.toit
   5[038] - load block 0
-  7[053] - invoke static invoke tests/type_propagation/non_local_branch_test.toit // {}
+  7[053] - invoke static invoke tests/type_propagation/non_local_branch_test.toit // [[block]] -> {}
  10[040] - pop 2
  12[083] - branch back T0
  17[022] - load null
@@ -83,13 +83,13 @@ id tests/type_propagation/non_local_branch_test.toit
 
 pick tests/type_propagation/non_local_branch_test.toit
   0[026] - load smi 100
-  2[053] - invoke static random <sdk>/core/utils.toit // {LargeInteger_|SmallInteger_}
+  2[053] - invoke static random <sdk>/core/utils.toit // [{SmallInteger_}] -> {LargeInteger_|SmallInteger_}
   5[026] - load smi 50
-  7[063] - invoke lt // {True_|False_}
+  7[063] - invoke lt // [{LargeInteger_|SmallInteger_}, {SmallInteger_}] -> {True_|False_}
   8[088] - return S1 0
 
 invoke tests/type_propagation/non_local_branch_test.toit
  - argument 0: [block]
   0[016] - load local 2
-  1[055] - invoke block S1 // {Null_}
+  1[055] - invoke block S1 // [[block]] -> {Null_}
   3[089] - return null S1 1
diff --git a/tests/type_propagation/gold/non_local_branch_test.gold-O2 b/tests/type_propagation/gold/non_local_branch_test.gold-O2
index 3d3f0ed99..1bd1ee53e 100644
--- a/tests/type_propagation/gold/non_local_branch_test.gold-O2
+++ b/tests/type_propagation/gold/non_local_branch_test.gold-O2
@@ -10,11 +10,11 @@ test_break tests/type_propagation/non_local_branch_test.toit
   0[026] - load smi 42
   2[029] - load [block] in test_break tests/type_propagation/non_local_branch_test.toit
   7[038] - load block 0
-  9[053] - invoke static invoke tests/type_propagation/non_local_branch_test.toit // {}
+  9[053] - invoke static invoke tests/type_propagation/non_local_branch_test.toit // [[block]] -> {}
  12[040] - pop 2
  14[083] - branch back T2
  19[014] - load local 0
- 20[053] - invoke static id tests/type_propagation/non_local_branch_test.toit // {String_}
+ 20[053] - invoke static id tests/type_propagation/non_local_branch_test.toit // [{String_}] -> {String_}
  23[089] - return null S2 0
 
 [block] in test_break tests/type_propagation/non_local_branch_test.toit
@@ -30,11 +30,11 @@ test_continue tests/type_propagation/non_local_branch_test.toit
   0[026] - load smi 42
   2[029] - load [block] in test_continue tests/type_propagation/non_local_branch_test.toit
   7[038] - load block 0
-  9[053] - invoke static invoke tests/type_propagation/non_local_branch_test.toit // {}
+  9[053] - invoke static invoke tests/type_propagation/non_local_branch_test.toit // [[block]] -> {}
  12[040] - pop 2
  14[083] - branch back T2
  19[014] - load local 0
- 20[053] - invoke static id tests/type_propagation/non_local_branch_test.toit // {float}
+ 20[053] - invoke static id tests/type_propagation/non_local_branch_test.toit // [{float}] -> {float}
  23[089] - return null S2 0
 
 [block] in test_continue tests/type_propagation/non_local_branch_test.toit
@@ -57,14 +57,14 @@ test_continue tests/type_propagation/non_local_branch_test.toit
 test_nested tests/type_propagation/non_local_branch_test.toit
   0[029] - load [block] in test_nested tests/type_propagation/non_local_branch_test.toit
   5[038] - load block 0
-  7[053] - invoke static invoke tests/type_propagation/non_local_branch_test.toit // {Null_}
+  7[053] - invoke static invoke tests/type_propagation/non_local_branch_test.toit // [[block]] -> {Null_}
  10[089] - return null S2 0
 
 [block] in test_nested tests/type_propagation/non_local_branch_test.toit
  - argument 0: [block]
   0[029] - load [block] in [block] in test_nested tests/type_propagation/non_local_branch_test.toit
   5[038] - load block 0
-  7[053] - invoke static invoke tests/type_propagation/non_local_branch_test.toit // {}
+  7[053] - invoke static invoke tests/type_propagation/non_local_branch_test.toit // [[block]] -> {}
  10[040] - pop 2
  12[083] - branch back T0
  17[022] - load null
@@ -83,13 +83,13 @@ id tests/type_propagation/non_local_branch_test.toit
 
 pick tests/type_propagation/non_local_branch_test.toit
   0[026] - load smi 100
-  2[053] - invoke static random <sdk>/core/utils.toit // {LargeInteger_|SmallInteger_}
+  2[053] - invoke static random <sdk>/core/utils.toit // [{SmallInteger_}] -> {LargeInteger_|SmallInteger_}
   5[026] - load smi 50
-  7[063] - invoke lt // {True_|False_}
+  7[063] - invoke lt // [{LargeInteger_|SmallInteger_}, {SmallInteger_}] -> {True_|False_}
   8[088] - return S1 0
 
 invoke tests/type_propagation/non_local_branch_test.toit
  - argument 0: [block]
   0[016] - load local 2
-  1[055] - invoke block S1 // {Null_}
+  1[055] - invoke block S1 // [[block]] -> {Null_}
   3[089] - return null S1 1
diff --git a/tests/type_propagation/gold/non_local_return_test.gold b/tests/type_propagation/gold/non_local_return_test.gold
index f5a5ca5e8..a7cb7a54a 100644
--- a/tests/type_propagation/gold/non_local_return_test.gold
+++ b/tests/type_propagation/gold/non_local_return_test.gold
@@ -7,7 +7,7 @@ main tests/type_propagation/non_local_return_test.toit
 test_simple tests/type_propagation/non_local_return_test.toit
   0[029] - load [block] in test_simple tests/type_propagation/non_local_return_test.toit
   5[038] - load block 0
-  7[053] - invoke static invoke tests/type_propagation/non_local_return_test.toit // {}
+  7[053] - invoke static invoke tests/type_propagation/non_local_return_test.toit // [[block]] -> {}
  10[040] - pop 2
  12[053] - invoke static unreachable <sdk>/core/exceptions.toit
  15[041] - pop 1
@@ -16,7 +16,7 @@ test_simple tests/type_propagation/non_local_return_test.toit
  - argument 0: [block]
   0[029] - load [block] in [block] in test_simple tests/type_propagation/non_local_return_test.toit
   5[038] - load block 0
-  7[053] - invoke static invoke tests/type_propagation/non_local_return_test.toit // {}
+  7[053] - invoke static invoke tests/type_propagation/non_local_return_test.toit // [[block]] -> {}
  10[004] - store local, pop S1
  12[088] - return S1 1
 
@@ -25,7 +25,7 @@ test_simple tests/type_propagation/non_local_return_test.toit
   0[029] - load [block] in [block] in [block] in test_simple tests/type_propagation/non_local_return_test.toit
   5[026] - load smi 3
   7[038] - load block 1
-  9[058] - invoke virtual repeat // {}
+  9[058] - invoke virtual repeat // [{SmallInteger_}, [block]] -> {}
  13[004] - store local, pop S1
  15[088] - return S1 1
 
@@ -41,7 +41,7 @@ test_simple tests/type_propagation/non_local_return_test.toit
 test_continue tests/type_propagation/non_local_return_test.toit
   0[029] - load [block] in test_continue tests/type_propagation/non_local_return_test.toit
   5[038] - load block 0
-  7[053] - invoke static invoke tests/type_propagation/non_local_return_test.toit // {String_}
+  7[053] - invoke static invoke tests/type_propagation/non_local_return_test.toit // [[block]] -> {String_}
  10[089] - return null S2 0
 
 [block] in test_continue tests/type_propagation/non_local_return_test.toit
@@ -49,7 +49,7 @@ test_continue tests/type_propagation/non_local_return_test.toit
   0[029] - load [block] in [block] in test_continue tests/type_propagation/non_local_return_test.toit
   5[026] - load smi 3
   7[038] - load block 1
-  9[058] - invoke virtual repeat // {}
+  9[058] - invoke virtual repeat // [{SmallInteger_}, [block]] -> {}
  13[004] - store local, pop S1
  15[088] - return S1 1
 
@@ -63,5 +63,5 @@ test_continue tests/type_propagation/non_local_return_test.toit
 invoke tests/type_propagation/non_local_return_test.toit
  - argument 0: [block]
   0[016] - load local 2
-  1[055] - invoke block S1 // {String_}
+  1[055] - invoke block S1 // [[block]] -> {String_}
   3[088] - return S1 1
diff --git a/tests/type_propagation/gold/non_local_return_test.gold-O2 b/tests/type_propagation/gold/non_local_return_test.gold-O2
index 8c9c56980..7f5fae4cb 100644
--- a/tests/type_propagation/gold/non_local_return_test.gold-O2
+++ b/tests/type_propagation/gold/non_local_return_test.gold-O2
@@ -7,14 +7,14 @@ main tests/type_propagation/non_local_return_test.toit
 test_simple tests/type_propagation/non_local_return_test.toit
   0[029] - load [block] in test_simple tests/type_propagation/non_local_return_test.toit
   5[038] - load block 0
-  7[053] - invoke static invoke tests/type_propagation/non_local_return_test.toit // {}
+  7[053] - invoke static invoke tests/type_propagation/non_local_return_test.toit // [[block]] -> {}
  10[041] - pop 1
 
 [block] in test_simple tests/type_propagation/non_local_return_test.toit
  - argument 0: [block]
   0[029] - load [block] in [block] in test_simple tests/type_propagation/non_local_return_test.toit
   5[038] - load block 0
-  7[053] - invoke static invoke tests/type_propagation/non_local_return_test.toit // {}
+  7[053] - invoke static invoke tests/type_propagation/non_local_return_test.toit // [[block]] -> {}
  10[004] - store local, pop S1
  12[088] - return S1 1
 
@@ -23,7 +23,7 @@ test_simple tests/type_propagation/non_local_return_test.toit
   0[029] - load [block] in [block] in [block] in test_simple tests/type_propagation/non_local_return_test.toit
   5[026] - load smi 3
   7[038] - load block 1
-  9[058] - invoke virtual repeat // {}
+  9[058] - invoke virtual repeat // [{SmallInteger_}, [block]] -> {}
  13[004] - store local, pop S1
  15[088] - return S1 1
 
@@ -39,7 +39,7 @@ test_simple tests/type_propagation/non_local_return_test.toit
 test_continue tests/type_propagation/non_local_return_test.toit
   0[029] - load [block] in test_continue tests/type_propagation/non_local_return_test.toit
   5[038] - load block 0
-  7[053] - invoke static invoke tests/type_propagation/non_local_return_test.toit // {String_}
+  7[053] - invoke static invoke tests/type_propagation/non_local_return_test.toit // [[block]] -> {String_}
  10[089] - return null S2 0
 
 [block] in test_continue tests/type_propagation/non_local_return_test.toit
@@ -47,7 +47,7 @@ test_continue tests/type_propagation/non_local_return_test.toit
   0[029] - load [block] in [block] in test_continue tests/type_propagation/non_local_return_test.toit
   5[026] - load smi 3
   7[038] - load block 1
-  9[058] - invoke virtual repeat // {}
+  9[058] - invoke virtual repeat // [{SmallInteger_}, [block]] -> {}
  13[004] - store local, pop S1
  15[088] - return S1 1
 
@@ -61,5 +61,5 @@ test_continue tests/type_propagation/non_local_return_test.toit
 invoke tests/type_propagation/non_local_return_test.toit
  - argument 0: [block]
   0[016] - load local 2
-  1[055] - invoke block S1 // {String_}
+  1[055] - invoke block S1 // [[block]] -> {String_}
   3[088] - return S1 1
diff --git a/tests/type_propagation/gold/null_equals_test.gold b/tests/type_propagation/gold/null_equals_test.gold
index 3453579d8..5c8db9f4f 100644
--- a/tests/type_propagation/gold/null_equals_test.gold
+++ b/tests/type_propagation/gold/null_equals_test.gold
@@ -2,62 +2,62 @@ main tests/type_propagation/null_equals_test.toit
   0[053] - invoke static obfuscate_null tests/type_propagation/null_equals_test.toit // {Null_}
   3[014] - load local 0
   4[022] - load null
-  5[062] - invoke eq // {True_}
-  6[053] - invoke static id tests/type_propagation/null_equals_test.toit // {True_}
+  5[062] - invoke eq // [{Null_}, {Null_}] -> {True_}
+  6[053] - invoke static id tests/type_propagation/null_equals_test.toit // [{True_}] -> {True_}
   9[041] - pop 1
  10[022] - load null
  11[015] - load local 1
- 12[062] - invoke eq // {True_}
- 13[053] - invoke static id tests/type_propagation/null_equals_test.toit // {True_}
+ 12[062] - invoke eq // [{Null_}, {Null_}] -> {True_}
+ 13[053] - invoke static id tests/type_propagation/null_equals_test.toit // [{True_}] -> {True_}
  16[041] - pop 1
  17[023] - load smi 0
  18[022] - load null
- 19[053] - invoke static Array_ <sdk>/core/collections.toit // {LargeArray_|SmallArray_}
+ 19[053] - invoke static Array_ <sdk>/core/collections.toit // [{SmallInteger_}, {Null_}] -> {LargeArray_|SmallArray_}
  22[014] - load local 0
  23[004] - store local, pop S1
- 25[053] - invoke static create_list_literal_from_array_ <sdk>/core/collections.toit // {List_}
+ 25[053] - invoke static create_list_literal_from_array_ <sdk>/core/collections.toit // [{LargeArray_|SmallArray_}] -> {List_}
  28[015] - load local 1
- 29[062] - invoke eq // {False_}
- 30[053] - invoke static id tests/type_propagation/null_equals_test.toit // {False_}
+ 29[062] - invoke eq // [{List_}, {Null_}] -> {False_}
+ 30[053] - invoke static id tests/type_propagation/null_equals_test.toit // [{False_}] -> {False_}
  33[002] - pop, load local S0
  35[023] - load smi 0
  36[022] - load null
- 37[053] - invoke static Array_ <sdk>/core/collections.toit // {LargeArray_|SmallArray_}
+ 37[053] - invoke static Array_ <sdk>/core/collections.toit // [{SmallInteger_}, {Null_}] -> {LargeArray_|SmallArray_}
  40[014] - load local 0
  41[004] - store local, pop S1
- 43[053] - invoke static create_list_literal_from_array_ <sdk>/core/collections.toit // {List_}
- 46[062] - invoke eq // {False_}
- 47[053] - invoke static id tests/type_propagation/null_equals_test.toit // {False_}
+ 43[053] - invoke static create_list_literal_from_array_ <sdk>/core/collections.toit // [{LargeArray_|SmallArray_}] -> {List_}
+ 46[062] - invoke eq // [{Null_}, {List_}] -> {False_}
+ 47[053] - invoke static id tests/type_propagation/null_equals_test.toit // [{False_}] -> {False_}
  50[041] - pop 1
  51[042] - allocate instance A
- 53[053] - invoke static A tests/type_propagation/null_equals_test.toit // {A}
+ 53[053] - invoke static A tests/type_propagation/null_equals_test.toit // [{A}] -> {A}
  56[042] - allocate instance A
- 58[053] - invoke static A tests/type_propagation/null_equals_test.toit // {A}
- 61[062] - invoke eq // {String_}
- 62[053] - invoke static id tests/type_propagation/null_equals_test.toit // {String_}
+ 58[053] - invoke static A tests/type_propagation/null_equals_test.toit // [{A}] -> {A}
+ 61[062] - invoke eq // [{A}, {A}] -> {String_}
+ 62[053] - invoke static id tests/type_propagation/null_equals_test.toit // [{String_}] -> {String_}
  65[041] - pop 1
  66[042] - allocate instance A
- 68[053] - invoke static A tests/type_propagation/null_equals_test.toit // {A}
+ 68[053] - invoke static A tests/type_propagation/null_equals_test.toit // [{A}] -> {A}
  71[022] - load null
- 72[062] - invoke eq // {False_}
- 73[053] - invoke static id tests/type_propagation/null_equals_test.toit // {False_}
+ 72[062] - invoke eq // [{A}, {Null_}] -> {False_}
+ 73[053] - invoke static id tests/type_propagation/null_equals_test.toit // [{False_}] -> {False_}
  76[041] - pop 1
  77[042] - allocate instance A
- 79[053] - invoke static A tests/type_propagation/null_equals_test.toit // {A}
+ 79[053] - invoke static A tests/type_propagation/null_equals_test.toit // [{A}] -> {A}
  82[015] - load local 1
- 83[062] - invoke eq // {False_}
- 84[053] - invoke static id tests/type_propagation/null_equals_test.toit // {False_}
+ 83[062] - invoke eq // [{A}, {Null_}] -> {False_}
+ 84[053] - invoke static id tests/type_propagation/null_equals_test.toit // [{False_}] -> {False_}
  87[041] - pop 1
  88[022] - load null
  89[042] - allocate instance A
- 91[053] - invoke static A tests/type_propagation/null_equals_test.toit // {A}
- 94[062] - invoke eq // {False_}
- 95[053] - invoke static id tests/type_propagation/null_equals_test.toit // {False_}
+ 91[053] - invoke static A tests/type_propagation/null_equals_test.toit // [{A}] -> {A}
+ 94[062] - invoke eq // [{Null_}, {A}] -> {False_}
+ 95[053] - invoke static id tests/type_propagation/null_equals_test.toit // [{False_}] -> {False_}
  98[002] - pop, load local S0
 100[042] - allocate instance A
-102[053] - invoke static A tests/type_propagation/null_equals_test.toit // {A}
-105[062] - invoke eq // {False_}
-106[053] - invoke static id tests/type_propagation/null_equals_test.toit // {False_}
+102[053] - invoke static A tests/type_propagation/null_equals_test.toit // [{A}] -> {A}
+105[062] - invoke eq // [{Null_}, {A}] -> {False_}
+106[053] - invoke static id tests/type_propagation/null_equals_test.toit // [{False_}] -> {False_}
 109[089] - return null S2 0
 
 obfuscate_null tests/type_propagation/null_equals_test.toit
diff --git a/tests/type_propagation/gold/null_equals_test.gold-O2 b/tests/type_propagation/gold/null_equals_test.gold-O2
index b78988d8c..e65eeb20c 100644
--- a/tests/type_propagation/gold/null_equals_test.gold-O2
+++ b/tests/type_propagation/gold/null_equals_test.gold-O2
@@ -2,62 +2,62 @@ main tests/type_propagation/null_equals_test.toit
   0[053] - invoke static obfuscate_null tests/type_propagation/null_equals_test.toit // {Null_}
   3[014] - load local 0
   4[022] - load null
-  5[062] - invoke eq // {True_}
-  6[053] - invoke static id tests/type_propagation/null_equals_test.toit // {True_}
+  5[062] - invoke eq // [{Null_}, {Null_}] -> {True_}
+  6[053] - invoke static id tests/type_propagation/null_equals_test.toit // [{True_}] -> {True_}
   9[041] - pop 1
  10[022] - load null
  11[015] - load local 1
- 12[062] - invoke eq // {True_}
- 13[053] - invoke static id tests/type_propagation/null_equals_test.toit // {True_}
+ 12[062] - invoke eq // [{Null_}, {Null_}] -> {True_}
+ 13[053] - invoke static id tests/type_propagation/null_equals_test.toit // [{True_}] -> {True_}
  16[041] - pop 1
  17[023] - load smi 0
  18[022] - load null
- 19[053] - invoke static Array_ <sdk>/core/collections.toit // {LargeArray_|SmallArray_}
+ 19[053] - invoke static Array_ <sdk>/core/collections.toit // [{SmallInteger_}, {Null_}] -> {LargeArray_|SmallArray_}
  22[014] - load local 0
  23[004] - store local, pop S1
- 25[053] - invoke static create_list_literal_from_array_ <sdk>/core/collections.toit // {List_}
+ 25[053] - invoke static create_list_literal_from_array_ <sdk>/core/collections.toit // [{LargeArray_|SmallArray_}] -> {List_}
  28[015] - load local 1
- 29[062] - invoke eq // {False_}
- 30[053] - invoke static id tests/type_propagation/null_equals_test.toit // {False_}
+ 29[062] - invoke eq // [{List_}, {Null_}] -> {False_}
+ 30[053] - invoke static id tests/type_propagation/null_equals_test.toit // [{False_}] -> {False_}
  33[002] - pop, load local S0
  35[023] - load smi 0
  36[022] - load null
- 37[053] - invoke static Array_ <sdk>/core/collections.toit // {LargeArray_|SmallArray_}
+ 37[053] - invoke static Array_ <sdk>/core/collections.toit // [{SmallInteger_}, {Null_}] -> {LargeArray_|SmallArray_}
  40[014] - load local 0
  41[004] - store local, pop S1
- 43[053] - invoke static create_list_literal_from_array_ <sdk>/core/collections.toit // {List_}
- 46[062] - invoke eq // {False_}
- 47[053] - invoke static id tests/type_propagation/null_equals_test.toit // {False_}
+ 43[053] - invoke static create_list_literal_from_array_ <sdk>/core/collections.toit // [{LargeArray_|SmallArray_}] -> {List_}
+ 46[062] - invoke eq // [{Null_}, {List_}] -> {False_}
+ 47[053] - invoke static id tests/type_propagation/null_equals_test.toit // [{False_}] -> {False_}
  50[041] - pop 1
  51[042] - allocate instance A
- 53[053] - invoke static A tests/type_propagation/null_equals_test.toit // {A}
+ 53[053] - invoke static A tests/type_propagation/null_equals_test.toit // [{A}] -> {A}
  56[042] - allocate instance A
- 58[053] - invoke static A tests/type_propagation/null_equals_test.toit // {A}
- 61[062] - invoke eq // {String_}
- 62[053] - invoke static id tests/type_propagation/null_equals_test.toit // {String_}
+ 58[053] - invoke static A tests/type_propagation/null_equals_test.toit // [{A}] -> {A}
+ 61[062] - invoke eq // [{A}, {A}] -> {String_}
+ 62[053] - invoke static id tests/type_propagation/null_equals_test.toit // [{String_}] -> {String_}
  65[041] - pop 1
  66[042] - allocate instance A
- 68[053] - invoke static A tests/type_propagation/null_equals_test.toit // {A}
+ 68[053] - invoke static A tests/type_propagation/null_equals_test.toit // [{A}] -> {A}
  71[022] - load null
- 72[062] - invoke eq // {False_}
- 73[053] - invoke static id tests/type_propagation/null_equals_test.toit // {False_}
+ 72[062] - invoke eq // [{A}, {Null_}] -> {False_}
+ 73[053] - invoke static id tests/type_propagation/null_equals_test.toit // [{False_}] -> {False_}
  76[041] - pop 1
  77[042] - allocate instance A
- 79[053] - invoke static A tests/type_propagation/null_equals_test.toit // {A}
+ 79[053] - invoke static A tests/type_propagation/null_equals_test.toit // [{A}] -> {A}
  82[015] - load local 1
- 83[062] - invoke eq // {False_}
- 84[053] - invoke static id tests/type_propagation/null_equals_test.toit // {False_}
+ 83[062] - invoke eq // [{A}, {Null_}] -> {False_}
+ 84[053] - invoke static id tests/type_propagation/null_equals_test.toit // [{False_}] -> {False_}
  87[041] - pop 1
  88[022] - load null
  89[042] - allocate instance A
- 91[053] - invoke static A tests/type_propagation/null_equals_test.toit // {A}
- 94[062] - invoke eq // {False_}
- 95[053] - invoke static id tests/type_propagation/null_equals_test.toit // {False_}
+ 91[053] - invoke static A tests/type_propagation/null_equals_test.toit // [{A}] -> {A}
+ 94[062] - invoke eq // [{Null_}, {A}] -> {False_}
+ 95[053] - invoke static id tests/type_propagation/null_equals_test.toit // [{False_}] -> {False_}
  98[002] - pop, load local S0
 100[042] - allocate instance A
-102[053] - invoke static A tests/type_propagation/null_equals_test.toit // {A}
-105[062] - invoke eq // {False_}
-106[053] - invoke static id tests/type_propagation/null_equals_test.toit // {False_}
+102[053] - invoke static A tests/type_propagation/null_equals_test.toit // [{A}] -> {A}
+105[062] - invoke eq // [{Null_}, {A}] -> {False_}
+106[053] - invoke static id tests/type_propagation/null_equals_test.toit // [{False_}] -> {False_}
 109[089] - return null S2 0
 
 obfuscate_null tests/type_propagation/null_equals_test.toit
diff --git a/tests/type_propagation/gold/richards_test.gold b/tests/type_propagation/gold/richards_test.gold
index 8c6a55051..de2c4cd1c 100644
--- a/tests/type_propagation/gold/richards_test.gold
+++ b/tests/type_propagation/gold/richards_test.gold
@@ -4,116 +4,116 @@ main tests/type_propagation/richards_test.toit
 
 run_richards tests/type_propagation/richards_test.toit
   0[042] - allocate instance Scheduler
-  2[053] - invoke static Scheduler tests/type_propagation/richards_test.toit // {Scheduler}
+  2[053] - invoke static Scheduler tests/type_propagation/richards_test.toit // [{Scheduler}] -> {Scheduler}
   5[014] - load local 0
   6[023] - load smi 0
   7[023] - load smi 0
   8[022] - load null
   9[027] - load smi 10000
- 12[053] - invoke static Scheduler.add_idle_task tests/type_propagation/richards_test.toit // {Null_}
+ 12[053] - invoke static Scheduler.add_idle_task tests/type_propagation/richards_test.toit // [{Scheduler}, {SmallInteger_}, {SmallInteger_}, {Null_}, {SmallInteger_}] -> {Null_}
  15[041] - pop 1
  16[042] - allocate instance Packet
  18[022] - load null
  19[025] - load smi 1
  20[025] - load smi 1
- 21[053] - invoke static Packet tests/type_propagation/richards_test.toit // {Packet}
+ 21[053] - invoke static Packet tests/type_propagation/richards_test.toit // [{Packet}, {Null_}, {SmallInteger_}, {SmallInteger_}] -> {Packet}
  24[042] - allocate instance Packet
  26[015] - load local 1
  27[025] - load smi 1
  28[025] - load smi 1
- 29[053] - invoke static Packet tests/type_propagation/richards_test.toit // {Packet}
+ 29[053] - invoke static Packet tests/type_propagation/richards_test.toit // [{Packet}, {Packet}, {SmallInteger_}, {SmallInteger_}] -> {Packet}
  32[004] - store local, pop S1
  34[015] - load local 1
  35[025] - load smi 1
  36[027] - load smi 1000
  39[017] - load local 3
- 40[053] - invoke static Scheduler.add_worker_task tests/type_propagation/richards_test.toit // {Null_}
+ 40[053] - invoke static Scheduler.add_worker_task tests/type_propagation/richards_test.toit // [{Scheduler}, {SmallInteger_}, {SmallInteger_}, {Packet}] -> {Null_}
  43[041] - pop 1
  44[042] - allocate instance Packet
  46[022] - load null
  47[026] - load smi 4
  49[023] - load smi 0
- 50[053] - invoke static Packet tests/type_propagation/richards_test.toit // {Packet}
+ 50[053] - invoke static Packet tests/type_propagation/richards_test.toit // [{Packet}, {Null_}, {SmallInteger_}, {SmallInteger_}] -> {Packet}
  53[004] - store local, pop S1
  55[042] - allocate instance Packet
  57[015] - load local 1
  58[026] - load smi 4
  60[023] - load smi 0
- 61[053] - invoke static Packet tests/type_propagation/richards_test.toit // {Packet}
+ 61[053] - invoke static Packet tests/type_propagation/richards_test.toit // [{Packet}, {Packet}, {SmallInteger_}, {SmallInteger_}] -> {Packet}
  64[004] - store local, pop S1
  66[042] - allocate instance Packet
  68[015] - load local 1
  69[026] - load smi 4
  71[023] - load smi 0
- 72[053] - invoke static Packet tests/type_propagation/richards_test.toit // {Packet}
+ 72[053] - invoke static Packet tests/type_propagation/richards_test.toit // [{Packet}, {Packet}, {SmallInteger_}, {SmallInteger_}] -> {Packet}
  75[004] - store local, pop S1
  77[015] - load local 1
  78[026] - load smi 2
  80[027] - load smi 2000
  83[017] - load local 3
- 84[053] - invoke static Scheduler.add_handler_task tests/type_propagation/richards_test.toit // {Null_}
+ 84[053] - invoke static Scheduler.add_handler_task tests/type_propagation/richards_test.toit // [{Scheduler}, {SmallInteger_}, {SmallInteger_}, {Packet}] -> {Null_}
  87[041] - pop 1
  88[042] - allocate instance Packet
  90[022] - load null
  91[026] - load smi 5
  93[023] - load smi 0
- 94[053] - invoke static Packet tests/type_propagation/richards_test.toit // {Packet}
+ 94[053] - invoke static Packet tests/type_propagation/richards_test.toit // [{Packet}, {Null_}, {SmallInteger_}, {SmallInteger_}] -> {Packet}
  97[004] - store local, pop S1
  99[042] - allocate instance Packet
 101[015] - load local 1
 102[026] - load smi 5
 104[023] - load smi 0
-105[053] - invoke static Packet tests/type_propagation/richards_test.toit // {Packet}
+105[053] - invoke static Packet tests/type_propagation/richards_test.toit // [{Packet}, {Packet}, {SmallInteger_}, {SmallInteger_}] -> {Packet}
 108[004] - store local, pop S1
 110[042] - allocate instance Packet
 112[015] - load local 1
 113[026] - load smi 5
 115[023] - load smi 0
-116[053] - invoke static Packet tests/type_propagation/richards_test.toit // {Packet}
+116[053] - invoke static Packet tests/type_propagation/richards_test.toit // [{Packet}, {Packet}, {SmallInteger_}, {SmallInteger_}] -> {Packet}
 119[004] - store local, pop S1
 121[015] - load local 1
 122[026] - load smi 3
 124[027] - load smi 3000
 127[017] - load local 3
-128[053] - invoke static Scheduler.add_handler_task tests/type_propagation/richards_test.toit // {Null_}
+128[053] - invoke static Scheduler.add_handler_task tests/type_propagation/richards_test.toit // [{Scheduler}, {SmallInteger_}, {SmallInteger_}, {Packet}] -> {Null_}
 131[002] - pop, load local S1
 133[026] - load smi 4
 135[027] - load smi 4000
 138[022] - load null
-139[053] - invoke static Scheduler.add_device_task tests/type_propagation/richards_test.toit // {Null_}
+139[053] - invoke static Scheduler.add_device_task tests/type_propagation/richards_test.toit // [{Scheduler}, {SmallInteger_}, {SmallInteger_}, {Null_}] -> {Null_}
 142[002] - pop, load local S1
 144[026] - load smi 5
 146[027] - load smi 5000
 149[022] - load null
-150[053] - invoke static Scheduler.add_device_task tests/type_propagation/richards_test.toit // {Null_}
+150[053] - invoke static Scheduler.add_device_task tests/type_propagation/richards_test.toit // [{Scheduler}, {SmallInteger_}, {SmallInteger_}, {Null_}] -> {Null_}
 153[002] - pop, load local S1
-155[053] - invoke static Scheduler.schedule tests/type_propagation/richards_test.toit // {Null_}
+155[053] - invoke static Scheduler.schedule tests/type_propagation/richards_test.toit // [{Scheduler}] -> {Null_}
 158[041] - pop 1
 159[029] - load [block] in run_richards tests/type_propagation/richards_test.toit
 164[038] - load block 0
-166[053] - invoke static assert_ <sdk>/core/assert_.toit // {Null_}
+166[053] - invoke static assert_ <sdk>/core/assert_.toit // [[block]] -> {Null_}
 169[040] - pop 2
 171[029] - load [block] in run_richards tests/type_propagation/richards_test.toit
 176[038] - load block 0
-178[053] - invoke static assert_ <sdk>/core/assert_.toit // {Null_}
+178[053] - invoke static assert_ <sdk>/core/assert_.toit // [[block]] -> {Null_}
 181[089] - return null S4 0
 
 [block] in run_richards tests/type_propagation/richards_test.toit
  - argument 0: [block]
   0[016] - load local 2
   1[005] - load outer S2 // {Scheduler}
-  3[007] - load field 0 // {Null_|LargeInteger_|SmallInteger_}
+  3[007] - load field 0 // [{Scheduler}] -> {Null_|LargeInteger_|SmallInteger_}
   5[027] - load smi 23246
-  8[062] - invoke eq // {True_|False_}
+  8[062] - invoke eq // [{Null_|LargeInteger_|SmallInteger_}, {SmallInteger_}] -> {True_|False_}
   9[088] - return S1 1
 
 [block] in run_richards tests/type_propagation/richards_test.toit
  - argument 0: [block]
   0[016] - load local 2
   1[005] - load outer S2 // {Scheduler}
-  3[007] - load field 1 // {Null_|LargeInteger_|SmallInteger_}
+  3[007] - load field 1 // [{Scheduler}] -> {Null_|LargeInteger_|SmallInteger_}
   5[027] - load smi 9297
-  8[062] - invoke eq // {True_|False_}
+  8[062] - invoke eq // [{Null_|LargeInteger_|SmallInteger_}, {SmallInteger_}] -> {True_|False_}
   9[088] - return S1 1
 
 Scheduler tests/type_propagation/richards_test.toit
@@ -127,7 +127,7 @@ Scheduler tests/type_propagation/richards_test.toit
   8[016] - load local 2
   9[026] - load smi 6
  11[022] - load null
- 12[053] - invoke static List <sdk>/core/collections.toit // {List_}
+ 12[053] - invoke static List <sdk>/core/collections.toit // [{SmallInteger_}, {Null_}] -> {List_}
  15[013] - store field, pop 2
  17[016] - load local 2
  18[088] - return S1 1
@@ -152,8 +152,8 @@ Scheduler.add_idle_task tests/type_propagation/richards_test.toit
  20[000] - load local S11
  22[025] - load smi 1
  23[000] - load local S9
- 25[053] - invoke static IdleTask tests/type_propagation/richards_test.toit // {IdleTask}
- 28[053] - invoke static Scheduler.add_running_task tests/type_propagation/richards_test.toit // {Null_}
+ 25[053] - invoke static IdleTask tests/type_propagation/richards_test.toit // [{IdleTask}, {Scheduler}, {SmallInteger_}, {SmallInteger_}] -> {IdleTask}
+ 28[053] - invoke static Scheduler.add_running_task tests/type_propagation/richards_test.toit // [{Scheduler}, {SmallInteger_}, {SmallInteger_}, {Null_}, {IdleTask}] -> {Null_}
  31[089] - return null S1 5
 
 Scheduler.add_worker_task tests/type_propagation/richards_test.toit
@@ -172,8 +172,8 @@ Scheduler.add_worker_task tests/type_propagation/richards_test.toit
  12[000] - load local S10
  14[026] - load smi 2
  16[023] - load smi 0
- 17[053] - invoke static WorkerTask tests/type_propagation/richards_test.toit // {WorkerTask}
- 20[053] - invoke static Scheduler.add_task tests/type_propagation/richards_test.toit // {Null_}
+ 17[053] - invoke static WorkerTask tests/type_propagation/richards_test.toit // [{WorkerTask}, {Scheduler}, {SmallInteger_}, {SmallInteger_}] -> {WorkerTask}
+ 20[053] - invoke static Scheduler.add_task tests/type_propagation/richards_test.toit // [{Scheduler}, {SmallInteger_}, {SmallInteger_}, {Packet}, {WorkerTask}] -> {Null_}
  23[089] - return null S1 4
 
 Scheduler.add_handler_task tests/type_propagation/richards_test.toit
@@ -190,8 +190,8 @@ Scheduler.add_handler_task tests/type_propagation/richards_test.toit
   9[019] - load local 5
  10[042] - allocate instance HandlerTask
  12[000] - load local S10
- 14[053] - invoke static HandlerTask tests/type_propagation/richards_test.toit // {HandlerTask}
- 17[053] - invoke static Scheduler.add_task tests/type_propagation/richards_test.toit // {Null_}
+ 14[053] - invoke static HandlerTask tests/type_propagation/richards_test.toit // [{HandlerTask}, {Scheduler}] -> {HandlerTask}
+ 17[053] - invoke static Scheduler.add_task tests/type_propagation/richards_test.toit // [{Scheduler}, {SmallInteger_}, {SmallInteger_}, {Packet}, {HandlerTask}] -> {Null_}
  20[089] - return null S1 4
 
 Scheduler.add_device_task tests/type_propagation/richards_test.toit
@@ -209,8 +209,8 @@ Scheduler.add_device_task tests/type_propagation/richards_test.toit
  11[019] - load local 5
  12[042] - allocate instance DeviceTask
  14[000] - load local S10
- 16[053] - invoke static DeviceTask tests/type_propagation/richards_test.toit // {DeviceTask}
- 19[053] - invoke static Scheduler.add_task tests/type_propagation/richards_test.toit // {Null_}
+ 16[053] - invoke static DeviceTask tests/type_propagation/richards_test.toit // [{DeviceTask}, {Scheduler}] -> {DeviceTask}
+ 19[053] - invoke static Scheduler.add_task tests/type_propagation/richards_test.toit // [{Scheduler}, {SmallInteger_}, {SmallInteger_}, {Null_}, {DeviceTask}] -> {Null_}
  22[089] - return null S1 4
 
 Scheduler.add_running_task tests/type_propagation/richards_test.toit
@@ -228,9 +228,9 @@ Scheduler.add_running_task tests/type_propagation/richards_test.toit
  11[000] - load local S6
  13[000] - load local S6
  15[000] - load local S6
- 17[053] - invoke static Scheduler.add_task tests/type_propagation/richards_test.toit // {Null_}
- 20[010] - pop, load field local 70 // {*}
- 22[058] - invoke virtual set_running // {Null_}
+ 17[053] - invoke static Scheduler.add_task tests/type_propagation/richards_test.toit // [{Scheduler}, {SmallInteger_}, {SmallInteger_}, {Null_}, {IdleTask}] -> {Null_}
+ 20[010] - pop, load field local 70 // [{Scheduler}] -> {*}
+ 22[058] - invoke virtual set_running // [{*}] -> {Null_}
  26[089] - return null S1 5
 
 Scheduler.add_task tests/type_propagation/richards_test.toit
@@ -245,142 +245,142 @@ Scheduler.add_task tests/type_propagation/richards_test.toit
   5[048] - as class Packet?(40 - 41) // {True_}
   7[002] - pop, load local S6
   9[042] - allocate instance TaskControlBlock
- 11[009] - load field local 56 // {*}
+ 11[009] - load field local 56 // [{Scheduler}] -> {*}
  13[000] - load local S8
  15[000] - load local S8
  17[000] - load local S8
  19[000] - load local S8
- 21[053] - invoke static TaskControlBlock tests/type_propagation/richards_test.toit // {TaskControlBlock}
+ 21[053] - invoke static TaskControlBlock tests/type_propagation/richards_test.toit // [{TaskControlBlock}, {*}, {SmallInteger_}, {SmallInteger_}, {Null_|Packet}, {HandlerTask|WorkerTask|DeviceTask|IdleTask}] -> {TaskControlBlock}
  24[013] - store field, pop 4
  26[000] - load local S6
- 28[009] - load field local 71 // {*}
+ 28[009] - load field local 71 // [{Scheduler}] -> {*}
  30[013] - store field, pop 3
- 32[009] - load field local 38 // {Null_|List_}
+ 32[009] - load field local 38 // [{Scheduler}] -> {Null_|List_}
  34[000] - load local S6
- 36[009] - load field local 72 // {*}
- 38[079] - invoke at_put // {*}
+ 36[009] - load field local 72 // [{Scheduler}] -> {*}
+ 38[079] - invoke at_put // [{Null_|List_}, {SmallInteger_}, {*}] -> {*}
  39[089] - return null S1 5
 
 Scheduler.schedule tests/type_propagation/richards_test.toit
  - argument 0: {Scheduler}
   0[016] - load local 2
-  1[009] - load field local 51 // {*}
+  1[009] - load field local 51 // [{Scheduler}] -> {*}
   3[013] - store field, pop 4
-  5[009] - load field local 66 // {*}
+  5[009] - load field local 66 // [{Scheduler}] -> {*}
   7[082] - branch if false T52
- 10[009] - load field local 66 // {*}
- 12[058] - invoke virtual is_held_or_suspended // {True_|False_}
+ 10[009] - load field local 66 // [{Scheduler}] -> {*}
+ 12[058] - invoke virtual is_held_or_suspended // [{*}] -> {True_|False_}
  16[082] - branch if false T30
  19[016] - load local 2
- 20[009] - load field local 67 // {*}
- 22[060] - invoke virtual get link // {Null_|Packet|TaskControlBlock}
+ 20[009] - load field local 67 // [{Scheduler}] -> {*}
+ 22[060] - invoke virtual get link // [{*}] -> {Null_|Packet|TaskControlBlock}
  25[013] - store field, pop 4
  27[080] - branch T47
  30[016] - load local 2
- 31[009] - load field local 67 // {*}
- 33[060] - invoke virtual get id // {Null_|LargeInteger_|SmallInteger_|ByteArray_}
+ 31[009] - load field local 67 // [{Scheduler}] -> {*}
+ 33[060] - invoke virtual get id // [{*}] -> {Null_|LargeInteger_|SmallInteger_|ByteArray_}
  36[013] - store field, pop 5
  38[016] - load local 2
- 39[009] - load field local 67 // {*}
- 41[058] - invoke virtual run // {*}
+ 39[009] - load field local 67 // [{Scheduler}] -> {*}
+ 41[058] - invoke virtual run // [{*}] -> {*}
  45[013] - store field, pop 4
  47[083] - branch back T5
  52[089] - return null S0 1
 
 Scheduler.hold_current tests/type_propagation/richards_test.toit
  - argument 0: {Scheduler}
-  0[009] - load field local 18 // {Null_|LargeInteger_|SmallInteger_}
+  0[009] - load field local 18 // [{Scheduler}] -> {Null_|LargeInteger_|SmallInteger_}
   2[017] - load local 3
   3[015] - load local 1
   4[025] - load smi 1
-  5[073] - invoke add // {LargeInteger_|SmallInteger_}
+  5[073] - invoke add // [{Null_|LargeInteger_|SmallInteger_}, {SmallInteger_}] -> {LargeInteger_|SmallInteger_}
   6[013] - store field, pop 1
-  8[010] - pop, load field local 66 // {*}
- 10[058] - invoke virtual mark_as_held // {Null_}
- 14[010] - pop, load field local 66 // {*}
- 16[060] - invoke virtual get link // {Null_|Packet|TaskControlBlock}
+  8[010] - pop, load field local 66 // [{Scheduler}] -> {*}
+ 10[058] - invoke virtual mark_as_held // [{*}] -> {Null_}
+ 14[010] - pop, load field local 66 // [{Scheduler}] -> {*}
+ 16[060] - invoke virtual get link // [{*}] -> {Null_|Packet|TaskControlBlock}
  19[088] - return S1 1
 
 Scheduler.suspend_current tests/type_propagation/richards_test.toit
  - argument 0: {Scheduler}
-  0[009] - load field local 66 // {*}
-  2[058] - invoke virtual mark_as_suspended // {Null_}
-  6[010] - pop, load field local 66 // {*}
+  0[009] - load field local 66 // [{Scheduler}] -> {*}
+  2[058] - invoke virtual mark_as_suspended // [{*}] -> {Null_}
+  6[010] - pop, load field local 66 // [{Scheduler}] -> {*}
   8[088] - return S1 1
 
 Scheduler.release tests/type_propagation/richards_test.toit
  - argument 0: {Scheduler}
  - argument 1: {SmallInteger_}
-  0[009] - load field local 35 // {Null_|List_}
+  0[009] - load field local 35 // [{Scheduler}] -> {Null_|List_}
   2[017] - load local 3
-  3[078] - invoke at // {*}
+  3[078] - invoke at // [{Null_|List_}, {SmallInteger_}] -> {*}
   4[014] - load local 0
   5[081] - branch if true T12
   8[014] - load local 0
   9[088] - return S2 2
  12[014] - load local 0
- 13[058] - invoke virtual mark_as_not_held // {Null_}
+ 13[058] - invoke virtual mark_as_not_held // [{*}] -> {Null_}
  17[002] - pop, load local S0
- 19[060] - invoke virtual get priority // {Null_|SmallInteger_}
- 22[009] - load field local 69 // {*}
- 24[060] - invoke virtual get priority // {Null_|SmallInteger_}
- 27[064] - invoke gt // {True_|False_}
+ 19[060] - invoke virtual get priority // [{*}] -> {Null_|SmallInteger_}
+ 22[009] - load field local 69 // [{Scheduler}] -> {*}
+ 24[060] - invoke virtual get priority // [{*}] -> {Null_|SmallInteger_}
+ 27[064] - invoke gt // [{Null_|SmallInteger_}, {Null_|SmallInteger_}] -> {True_|False_}
  28[082] - branch if false T38
  31[014] - load local 0
  32[088] - return S2 2
  35[080] - branch T43
- 38[009] - load field local 68 // {*}
+ 38[009] - load field local 68 // [{Scheduler}] -> {*}
  40[088] - return S2 2
 
 Scheduler.queue tests/type_propagation/richards_test.toit
  - argument 0: {Scheduler}
  - argument 1: {Null_|Packet}
   0[052] - load local, as class, pop 2 - Packet(40 - 41) // {True_|False_}
-  2[009] - load field local 35 // {Null_|List_}
-  4[009] - load field local 19 // {Null_|LargeInteger_|SmallInteger_}
-  6[078] - invoke at // {*}
+  2[009] - load field local 35 // [{Scheduler}] -> {Null_|List_}
+  4[009] - load field local 19 // [{Packet}] -> {Null_|LargeInteger_|SmallInteger_}
+  6[078] - invoke at // [{Null_|List_}, {Null_|LargeInteger_|SmallInteger_}] -> {*}
   7[014] - load local 0
   8[081] - branch if true T15
  11[014] - load local 0
  12[088] - return S2 2
- 15[009] - load field local 4 // {Null_|LargeInteger_|SmallInteger_}
+ 15[009] - load field local 4 // [{Scheduler}] -> {Null_|LargeInteger_|SmallInteger_}
  17[019] - load local 5
  18[015] - load local 1
  19[025] - load smi 1
- 20[073] - invoke add // {LargeInteger_|SmallInteger_}
+ 20[073] - invoke add // [{Null_|LargeInteger_|SmallInteger_}, {SmallInteger_}] -> {LargeInteger_|SmallInteger_}
  21[013] - store field, pop 0
  23[002] - pop, load local S3
  25[022] - load null
  26[048] - as class Packet?(40 - 41) // {True_}
  28[013] - store field, pop 0
  30[017] - load local 3
- 31[009] - load field local 85 // {Null_|LargeInteger_|SmallInteger_|ByteArray_}
+ 31[009] - load field local 85 // [{Scheduler}] -> {Null_|LargeInteger_|SmallInteger_|ByteArray_}
  33[048] - as class LargeInteger_(22 - 24) // {True_|False_}
  35[013] - store field, pop 1
  37[014] - load local 0
- 38[009] - load field local 69 // {*}
+ 38[009] - load field local 69 // [{Scheduler}] -> {*}
  40[019] - load local 5
- 41[058] - invoke virtual check_priority_add // {*}
+ 41[058] - invoke virtual check_priority_add // [{*}, {*}, {Packet}] -> {*}
  45[088] - return S2 2
 
 STATE_NOT_HELD tests/type_propagation/richards_test.toit
   0[026] - load smi 4
-  2[058] - invoke virtual ~ // {SmallInteger_}
+  2[058] - invoke virtual ~ // [{SmallInteger_}] -> {SmallInteger_}
   6[088] - return S1 0
 
 TaskControlBlock.link tests/type_propagation/richards_test.toit
  - argument 0: {TaskControlBlock}
-  0[009] - load field local 2 // {Null_|TaskControlBlock}
+  0[009] - load field local 2 // [{TaskControlBlock}] -> {Null_|TaskControlBlock}
   2[088] - return S1 1
 
 TaskControlBlock.id tests/type_propagation/richards_test.toit
  - argument 0: {TaskControlBlock}
-  0[009] - load field local 18 // {Null_|SmallInteger_}
+  0[009] - load field local 18 // [{TaskControlBlock}] -> {Null_|SmallInteger_}
   2[088] - return S1 1
 
 TaskControlBlock.priority tests/type_propagation/richards_test.toit
  - argument 0: {TaskControlBlock}
-  0[009] - load field local 34 // {Null_|SmallInteger_}
+  0[009] - load field local 34 // [{TaskControlBlock}] -> {Null_|SmallInteger_}
   2[088] - return S1 1
 
 TaskControlBlock tests/type_propagation/richards_test.toit
@@ -414,7 +414,7 @@ TaskControlBlock tests/type_propagation/richards_test.toit
  38[013] - store field, pop 5
  40[000] - load local S7
  42[026] - load smi 2
- 44[009] - load field local 57 // {Null_|Packet}
+ 44[009] - load field local 57 // [{TaskControlBlock}] -> {Null_|Packet}
  46[082] - branch if false T52
  49[041] - pop 1
  50[026] - load smi 3
@@ -433,9 +433,9 @@ TaskControlBlock.set_running tests/type_propagation/richards_test.toit
 TaskControlBlock.mark_as_not_held tests/type_propagation/richards_test.toit
  - argument 0: {TaskControlBlock}
   0[016] - load local 2
-  1[009] - load field local 83 // {Null_|LargeInteger_|SmallInteger_}
+  1[009] - load field local 83 // [{TaskControlBlock}] -> {Null_|LargeInteger_|SmallInteger_}
   3[033] - load global var lazy G0 // {SmallInteger_}
-  5[069] - invoke bit and // {LargeInteger_|SmallInteger_}
+  5[069] - invoke bit and // [{Null_|LargeInteger_|SmallInteger_}, {SmallInteger_}] -> {LargeInteger_|SmallInteger_}
   6[048] - as class LargeInteger_(22 - 24) // {True_}
   8[013] - store field, pop 5
  10[089] - return null S0 1
@@ -443,37 +443,37 @@ TaskControlBlock.mark_as_not_held tests/type_propagation/richards_test.toit
 TaskControlBlock.mark_as_held tests/type_propagation/richards_test.toit
  - argument 0: {TaskControlBlock}
   0[016] - load local 2
-  1[009] - load field local 83 // {Null_|LargeInteger_|SmallInteger_}
+  1[009] - load field local 83 // [{TaskControlBlock}] -> {Null_|LargeInteger_|SmallInteger_}
   3[026] - load smi 4
-  5[067] - invoke bit or // {LargeInteger_|SmallInteger_}
+  5[067] - invoke bit or // [{Null_|LargeInteger_|SmallInteger_}, {SmallInteger_}] -> {LargeInteger_|SmallInteger_}
   6[048] - as class LargeInteger_(22 - 24) // {True_}
   8[013] - store field, pop 5
  10[089] - return null S0 1
 
 TaskControlBlock.is_held_or_suspended tests/type_propagation/richards_test.toit
  - argument 0: {TaskControlBlock}
-  0[009] - load field local 82 // {Null_|LargeInteger_|SmallInteger_}
+  0[009] - load field local 82 // [{TaskControlBlock}] -> {Null_|LargeInteger_|SmallInteger_}
   2[026] - load smi 4
-  4[069] - invoke bit and // {LargeInteger_|SmallInteger_}
+  4[069] - invoke bit and // [{Null_|LargeInteger_|SmallInteger_}, {SmallInteger_}] -> {LargeInteger_|SmallInteger_}
   5[023] - load smi 0
-  6[062] - invoke eq // {True_|False_}
+  6[062] - invoke eq // [{LargeInteger_|SmallInteger_}, {SmallInteger_}] -> {True_|False_}
   7[081] - branch if true T15
  10[020] - load literal true
  12[080] - branch T17
  15[020] - load literal false
  17[014] - load local 0
  18[081] - branch if true T26
- 21[010] - pop, load field local 82 // {Null_|LargeInteger_|SmallInteger_}
+ 21[010] - pop, load field local 82 // [{TaskControlBlock}] -> {Null_|LargeInteger_|SmallInteger_}
  23[026] - load smi 2
- 25[062] - invoke eq // {True_|False_}
+ 25[062] - invoke eq // [{Null_|LargeInteger_|SmallInteger_}, {SmallInteger_}] -> {True_|False_}
  26[088] - return S1 1
 
 TaskControlBlock.mark_as_suspended tests/type_propagation/richards_test.toit
  - argument 0: {TaskControlBlock}
   0[016] - load local 2
-  1[009] - load field local 83 // {Null_|LargeInteger_|SmallInteger_}
+  1[009] - load field local 83 // [{TaskControlBlock}] -> {Null_|LargeInteger_|SmallInteger_}
   3[026] - load smi 2
-  5[067] - invoke bit or // {LargeInteger_|SmallInteger_}
+  5[067] - invoke bit or // [{Null_|LargeInteger_|SmallInteger_}, {SmallInteger_}] -> {LargeInteger_|SmallInteger_}
   6[048] - as class LargeInteger_(22 - 24) // {True_}
   8[013] - store field, pop 5
  10[089] - return null S0 1
@@ -481,9 +481,9 @@ TaskControlBlock.mark_as_suspended tests/type_propagation/richards_test.toit
 TaskControlBlock.mark_as_runnable tests/type_propagation/richards_test.toit
  - argument 0: {TaskControlBlock}
   0[016] - load local 2
-  1[009] - load field local 83 // {Null_|LargeInteger_|SmallInteger_}
+  1[009] - load field local 83 // [{TaskControlBlock}] -> {Null_|LargeInteger_|SmallInteger_}
   3[025] - load smi 1
-  4[067] - invoke bit or // {LargeInteger_|SmallInteger_}
+  4[067] - invoke bit or // [{Null_|LargeInteger_|SmallInteger_}, {SmallInteger_}] -> {LargeInteger_|SmallInteger_}
   5[048] - as class LargeInteger_(22 - 24) // {True_}
   7[013] - store field, pop 5
   9[089] - return null S0 1
@@ -491,54 +491,54 @@ TaskControlBlock.mark_as_runnable tests/type_propagation/richards_test.toit
 TaskControlBlock.run tests/type_propagation/richards_test.toit
  - argument 0: {TaskControlBlock}
   0[022] - load null
-  1[009] - load field local 83 // {Null_|LargeInteger_|SmallInteger_}
+  1[009] - load field local 83 // [{TaskControlBlock}] -> {Null_|LargeInteger_|SmallInteger_}
   3[026] - load smi 3
-  5[062] - invoke eq // {True_|False_}
+  5[062] - invoke eq // [{Null_|LargeInteger_|SmallInteger_}, {SmallInteger_}] -> {True_|False_}
   6[082] - branch if false T35
-  9[009] - load field local 51 // {Null_|Packet}
+  9[009] - load field local 51 // [{TaskControlBlock}] -> {Null_|Packet}
  11[004] - store local, pop S1
  13[017] - load local 3
  14[015] - load local 1
- 15[060] - invoke virtual get link // {Null_|Packet}
+ 15[060] - invoke virtual get link // [{Null_|Packet}] -> {Null_|Packet}
  18[048] - as class Packet?(40 - 41) // {True_}
  20[013] - store field, pop 3
  22[017] - load local 3
  23[023] - load smi 0
- 24[009] - load field local 53 // {Null_|Packet}
+ 24[009] - load field local 53 // [{TaskControlBlock}] -> {Null_|Packet}
  26[082] - branch if false T31
  29[041] - pop 1
  30[025] - load smi 1
  31[048] - as class LargeInteger_(22 - 24) // {True_}
  33[013] - store field, pop 5
- 35[009] - load field local 67 // {Null_|HandlerTask|WorkerTask|DeviceTask|IdleTask}
+ 35[009] - load field local 67 // [{TaskControlBlock}] -> {Null_|HandlerTask|WorkerTask|DeviceTask|IdleTask}
  37[015] - load local 1
- 38[058] - invoke virtual run // {*}
+ 38[058] - invoke virtual run // [{Null_|HandlerTask|WorkerTask|DeviceTask|IdleTask}, {Null_|Packet}] -> {*}
  42[088] - return S2 1
 
 TaskControlBlock.check_priority_add tests/type_propagation/richards_test.toit
  - argument 0: {TaskControlBlock}
  - argument 1: {*}
  - argument 2: {Packet}
-  0[009] - load field local 52 // {Null_|Packet}
+  0[009] - load field local 52 // [{TaskControlBlock}] -> {Null_|Packet}
   2[081] - branch if true T32
   5[018] - load local 4
   6[017] - load local 3
   7[048] - as class Packet?(40 - 41) // {True_}
   9[013] - store field, pop 3
  11[018] - load local 4
- 12[053] - invoke static TaskControlBlock.mark_as_runnable tests/type_propagation/richards_test.toit // {Null_}
- 15[010] - pop, load field local 36 // {Null_|SmallInteger_}
+ 12[053] - invoke static TaskControlBlock.mark_as_runnable tests/type_propagation/richards_test.toit // [{TaskControlBlock}] -> {Null_}
+ 15[010] - pop, load field local 36 // [{TaskControlBlock}] -> {Null_|SmallInteger_}
  17[018] - load local 4
- 18[060] - invoke virtual get priority // {Null_|SmallInteger_}
- 21[064] - invoke gt // {True_|False_}
+ 18[060] - invoke virtual get priority // [{*}] -> {Null_|SmallInteger_}
+ 21[064] - invoke gt // [{Null_|SmallInteger_}, {Null_|SmallInteger_}] -> {True_|False_}
  22[082] - branch if false T29
  25[018] - load local 4
  26[088] - return S1 3
  29[080] - branch T44
  32[018] - load local 4
  33[017] - load local 3
- 34[009] - load field local 54 // {Null_|Packet}
- 36[058] - invoke virtual add_to // {Packet}
+ 34[009] - load field local 54 // [{TaskControlBlock}] -> {Null_|Packet}
+ 36[058] - invoke virtual add_to // [{Packet}, {Null_|Packet}] -> {Packet}
  40[048] - as class Packet?(40 - 41) // {True_}
  42[013] - store field, pop 3
  44[017] - load local 3
@@ -567,48 +567,48 @@ IdleTask tests/type_propagation/richards_test.toit
 IdleTask.run tests/type_propagation/richards_test.toit
  - argument 0: {IdleTask}
  - argument 1: {Null_|Packet}
-  0[009] - load field local 35 // {Null_|LargeInteger_|SmallInteger_}
+  0[009] - load field local 35 // [{IdleTask}] -> {Null_|LargeInteger_|SmallInteger_}
   2[018] - load local 4
   3[015] - load local 1
   4[025] - load smi 1
-  5[074] - invoke sub // {LargeInteger_|SmallInteger_}
+  5[074] - invoke sub // [{Null_|LargeInteger_|SmallInteger_}, {SmallInteger_}] -> {LargeInteger_|SmallInteger_}
   6[048] - as class LargeInteger_(22 - 24) // {True_}
   8[013] - store field, pop 2
- 10[010] - pop, load field local 35 // {Null_|LargeInteger_|SmallInteger_}
+ 10[010] - pop, load field local 35 // [{IdleTask}] -> {Null_|LargeInteger_|SmallInteger_}
  12[023] - load smi 0
- 13[062] - invoke eq // {True_|False_}
+ 13[062] - invoke eq // [{Null_|LargeInteger_|SmallInteger_}, {SmallInteger_}] -> {True_|False_}
  14[082] - branch if false T25
- 17[009] - load field local 3 // {Null_|Scheduler}
- 19[053] - invoke static Scheduler.hold_current tests/type_propagation/richards_test.toit // {Null_|Packet|TaskControlBlock}
+ 17[009] - load field local 3 // [{IdleTask}] -> {Null_|Scheduler}
+ 19[053] - invoke static Scheduler.hold_current tests/type_propagation/richards_test.toit // [{Null_|Scheduler}] -> {Null_|Packet|TaskControlBlock}
  22[088] - return S1 2
- 25[009] - load field local 19 // {Null_|LargeInteger_|SmallInteger_}
+ 25[009] - load field local 19 // [{IdleTask}] -> {Null_|LargeInteger_|SmallInteger_}
  27[025] - load smi 1
- 28[069] - invoke bit and // {LargeInteger_|SmallInteger_}
+ 28[069] - invoke bit and // [{Null_|LargeInteger_|SmallInteger_}, {SmallInteger_}] -> {LargeInteger_|SmallInteger_}
  29[023] - load smi 0
- 30[062] - invoke eq // {True_|False_}
+ 30[062] - invoke eq // [{LargeInteger_|SmallInteger_}, {SmallInteger_}] -> {True_|False_}
  31[082] - branch if false T56
  34[017] - load local 3
- 35[009] - load field local 20 // {Null_|LargeInteger_|SmallInteger_}
+ 35[009] - load field local 20 // [{IdleTask}] -> {Null_|LargeInteger_|SmallInteger_}
  37[025] - load smi 1
- 38[071] - invoke bit shr // {LargeInteger_|SmallInteger_}
+ 38[071] - invoke bit shr // [{Null_|LargeInteger_|SmallInteger_}, {SmallInteger_}] -> {LargeInteger_|SmallInteger_}
  39[048] - as class LargeInteger_(22 - 24) // {True_}
  41[013] - store field, pop 1
- 43[009] - load field local 3 // {Null_|Scheduler}
+ 43[009] - load field local 3 // [{IdleTask}] -> {Null_|Scheduler}
  45[026] - load smi 4
- 47[053] - invoke static Scheduler.release tests/type_propagation/richards_test.toit // {*}
+ 47[053] - invoke static Scheduler.release tests/type_propagation/richards_test.toit // [{Null_|Scheduler}, {SmallInteger_}] -> {*}
  50[088] - return S1 2
  53[080] - branch T79
  56[017] - load local 3
- 57[009] - load field local 20 // {Null_|LargeInteger_|SmallInteger_}
+ 57[009] - load field local 20 // [{IdleTask}] -> {Null_|LargeInteger_|SmallInteger_}
  59[025] - load smi 1
- 60[071] - invoke bit shr // {LargeInteger_|SmallInteger_}
+ 60[071] - invoke bit shr // [{Null_|LargeInteger_|SmallInteger_}, {SmallInteger_}] -> {LargeInteger_|SmallInteger_}
  61[027] - load smi 53256
- 64[068] - invoke bit xor // {LargeInteger_|SmallInteger_}
+ 64[068] - invoke bit xor // [{LargeInteger_|SmallInteger_}, {SmallInteger_}] -> {LargeInteger_|SmallInteger_}
  65[048] - as class LargeInteger_(22 - 24) // {True_}
  67[013] - store field, pop 1
- 69[009] - load field local 3 // {Null_|Scheduler}
+ 69[009] - load field local 3 // [{IdleTask}] -> {Null_|Scheduler}
  71[026] - load smi 5
- 73[053] - invoke static Scheduler.release tests/type_propagation/richards_test.toit // {*}
+ 73[053] - invoke static Scheduler.release tests/type_propagation/richards_test.toit // [{Null_|Scheduler}, {SmallInteger_}] -> {*}
  76[088] - return S1 2
 
 DeviceTask tests/type_propagation/richards_test.toit
@@ -626,25 +626,25 @@ DeviceTask.run tests/type_propagation/richards_test.toit
  - argument 1: {Null_|Packet}
   0[016] - load local 2
   1[081] - branch if true T35
-  4[009] - load field local 19 // {Null_|Packet}
+  4[009] - load field local 19 // [{DeviceTask}] -> {Null_|Packet}
   6[081] - branch if true T17
-  9[009] - load field local 3 // {Null_|Scheduler}
- 11[053] - invoke static Scheduler.suspend_current tests/type_propagation/richards_test.toit // {*}
+  9[009] - load field local 3 // [{DeviceTask}] -> {Null_|Scheduler}
+ 11[053] - invoke static Scheduler.suspend_current tests/type_propagation/richards_test.toit // [{Null_|Scheduler}] -> {*}
  14[088] - return S1 2
- 17[009] - load field local 19 // {Null_|Packet}
+ 17[009] - load field local 19 // [{DeviceTask}] -> {Null_|Packet}
  19[018] - load local 4
  20[022] - load null
  21[013] - store field, pop 1
- 23[009] - load field local 4 // {Null_|Scheduler}
+ 23[009] - load field local 4 // [{DeviceTask}] -> {Null_|Scheduler}
  25[015] - load local 1
- 26[053] - invoke static Scheduler.queue tests/type_propagation/richards_test.toit // {*}
+ 26[053] - invoke static Scheduler.queue tests/type_propagation/richards_test.toit // [{Null_|Scheduler}, {Null_|Packet}] -> {*}
  29[088] - return S2 2
  32[080] - branch T47
  35[017] - load local 3
  36[017] - load local 3
  37[013] - store field, pop 1
- 39[009] - load field local 3 // {Null_|Scheduler}
- 41[053] - invoke static Scheduler.hold_current tests/type_propagation/richards_test.toit // {Null_|Packet|TaskControlBlock}
+ 39[009] - load field local 3 // [{DeviceTask}] -> {Null_|Scheduler}
+ 41[053] - invoke static Scheduler.hold_current tests/type_propagation/richards_test.toit // [{Null_|Scheduler}] -> {Null_|Packet|TaskControlBlock}
  44[088] - return S1 2
 
 WorkerTask tests/type_propagation/richards_test.toit
@@ -672,60 +672,60 @@ WorkerTask.run tests/type_propagation/richards_test.toit
  - argument 1: {Null_|Packet}
   0[016] - load local 2
   1[081] - branch if true T12
-  4[009] - load field local 3 // {Null_|Scheduler}
-  6[053] - invoke static Scheduler.suspend_current tests/type_propagation/richards_test.toit // {*}
+  4[009] - load field local 3 // [{WorkerTask}] -> {Null_|Scheduler}
+  6[053] - invoke static Scheduler.suspend_current tests/type_propagation/richards_test.toit // [{Null_|Scheduler}] -> {*}
   9[088] - return S1 2
  12[017] - load local 3
  13[026] - load smi 2
- 15[009] - load field local 21 // {Null_|SmallInteger_}
+ 15[009] - load field local 21 // [{WorkerTask}] -> {Null_|SmallInteger_}
  17[026] - load smi 2
- 19[062] - invoke eq // {True_|False_}
+ 19[062] - invoke eq // [{Null_|SmallInteger_}, {SmallInteger_}] -> {True_|False_}
  20[082] - branch if false T26
  23[041] - pop 1
  24[026] - load smi 3
  26[048] - as class LargeInteger_(22 - 24) // {True_}
  28[013] - store field, pop 1
  30[016] - load local 2
- 31[009] - load field local 20 // {Null_|SmallInteger_}
- 33[061] - invoke virtual set id // {SmallInteger_}
+ 31[009] - load field local 20 // [{WorkerTask}] -> {Null_|SmallInteger_}
+ 33[061] - invoke virtual set id // [{Null_|Packet}, {Null_|SmallInteger_}] -> {SmallInteger_}
  36[002] - pop, load local S2
  38[023] - load smi 0
- 39[061] - invoke virtual set a1 // {SmallInteger_}
+ 39[061] - invoke virtual set a1 // [{Packet}, {SmallInteger_}] -> {SmallInteger_}
  42[041] - pop 1
  43[023] - load smi 0
  44[014] - load local 0
  45[026] - load smi 4
- 47[063] - invoke lt // {True_|False_}
+ 47[063] - invoke lt // [{LargeInteger_|SmallInteger_}, {SmallInteger_}] -> {True_|False_}
  48[082] - branch if false T93
  51[018] - load local 4
- 52[009] - load field local 37 // {Null_|LargeInteger_|SmallInteger_}
+ 52[009] - load field local 37 // [{WorkerTask}] -> {Null_|LargeInteger_|SmallInteger_}
  54[025] - load smi 1
- 55[073] - invoke add // {LargeInteger_|SmallInteger_}
+ 55[073] - invoke add // [{Null_|LargeInteger_|SmallInteger_}, {SmallInteger_}] -> {LargeInteger_|SmallInteger_}
  56[048] - as class LargeInteger_(22 - 24) // {True_}
  58[011] - store field 2
  60[026] - load smi 26
- 62[064] - invoke gt // {True_|False_}
+ 62[064] - invoke gt // [{LargeInteger_|SmallInteger_}, {SmallInteger_}] -> {True_|False_}
  63[082] - branch if false T72
  66[018] - load local 4
  67[025] - load smi 1
  68[048] - as class LargeInteger_(22 - 24) // {True_}
  70[013] - store field, pop 2
  72[017] - load local 3
- 73[060] - invoke virtual get a2 // {Null_|List_}
+ 73[060] - invoke virtual get a2 // [{Packet}] -> {Null_|List_}
  76[015] - load local 1
- 77[009] - load field local 38 // {Null_|LargeInteger_|SmallInteger_}
- 79[079] - invoke at_put // {*}
+ 77[009] - load field local 38 // [{WorkerTask}] -> {Null_|LargeInteger_|SmallInteger_}
+ 79[079] - invoke at_put // [{Null_|List_}, {LargeInteger_|SmallInteger_}, {Null_|LargeInteger_|SmallInteger_}] -> {*}
  80[041] - pop 1
  81[014] - load local 0
  82[014] - load local 0
  83[025] - load smi 1
- 84[073] - invoke add // {LargeInteger_|SmallInteger_}
+ 84[073] - invoke add // [{LargeInteger_|SmallInteger_}, {SmallInteger_}] -> {LargeInteger_|SmallInteger_}
  85[004] - store local, pop S2
  87[041] - pop 1
  88[083] - branch back T44
- 93[010] - pop, load field local 3 // {Null_|Scheduler}
+ 93[010] - pop, load field local 3 // [{WorkerTask}] -> {Null_|Scheduler}
  95[017] - load local 3
- 96[053] - invoke static Scheduler.queue tests/type_propagation/richards_test.toit // {*}
+ 96[053] - invoke static Scheduler.queue tests/type_propagation/richards_test.toit // [{Null_|Scheduler}, {Packet}] -> {*}
  99[088] - return S1 2
 
 HandlerTask tests/type_propagation/richards_test.toit
@@ -744,64 +744,64 @@ HandlerTask.run tests/type_propagation/richards_test.toit
   0[016] - load local 2
   1[082] - branch if false T36
   4[016] - load local 2
-  5[060] - invoke virtual get kind // {Null_|SmallInteger_}
+  5[060] - invoke virtual get kind // [{Null_|Packet}] -> {Null_|SmallInteger_}
   8[025] - load smi 1
-  9[062] - invoke eq // {True_|False_}
+  9[062] - invoke eq // [{Null_|SmallInteger_}, {SmallInteger_}] -> {True_|False_}
  10[082] - branch if false T26
  13[017] - load local 3
  14[017] - load local 3
- 15[009] - load field local 21 // {Null_|Packet}
- 17[058] - invoke virtual add_to // {Packet}
+ 15[009] - load field local 21 // [{HandlerTask}] -> {Null_|Packet}
+ 17[058] - invoke virtual add_to // [{Packet}, {Null_|Packet}] -> {Packet}
  21[013] - store field, pop 1
  23[080] - branch T36
  26[017] - load local 3
  27[017] - load local 3
- 28[009] - load field local 37 // {Null_|Packet}
- 30[058] - invoke virtual add_to // {Packet}
+ 28[009] - load field local 37 // [{HandlerTask}] -> {Null_|Packet}
+ 30[058] - invoke virtual add_to // [{Packet}, {Null_|Packet}] -> {Packet}
  34[013] - store field, pop 2
- 36[009] - load field local 19 // {Null_|Packet}
+ 36[009] - load field local 19 // [{HandlerTask}] -> {Null_|Packet}
  38[082] - branch if false T119
- 41[009] - load field local 19 // {Null_|Packet}
- 43[060] - invoke virtual get a1 // {*}
+ 41[009] - load field local 19 // [{HandlerTask}] -> {Null_|Packet}
+ 43[060] - invoke virtual get a1 // [{Null_|Packet}] -> {*}
  46[014] - load local 0
  47[026] - load smi 4
- 49[063] - invoke lt // {True_|False_}
+ 49[063] - invoke lt // [{*}, {SmallInteger_}] -> {True_|False_}
  50[082] - branch if false T99
- 53[009] - load field local 36 // {Null_|Packet}
+ 53[009] - load field local 36 // [{HandlerTask}] -> {Null_|Packet}
  55[082] - branch if false T96
- 58[009] - load field local 36 // {Null_|Packet}
+ 58[009] - load field local 36 // [{HandlerTask}] -> {Null_|Packet}
  60[019] - load local 5
- 61[009] - load field local 38 // {Null_|Packet}
- 63[060] - invoke virtual get link // {Null_|Packet}
+ 61[009] - load field local 38 // [{HandlerTask}] -> {Null_|Packet}
+ 63[060] - invoke virtual get link // [{Null_|Packet}] -> {Null_|Packet}
  66[013] - store field, pop 2
  68[014] - load local 0
- 69[009] - load field local 22 // {Null_|Packet}
- 71[060] - invoke virtual get a2 // {Null_|List_}
+ 69[009] - load field local 22 // [{HandlerTask}] -> {Null_|Packet}
+ 71[060] - invoke virtual get a2 // [{Null_|Packet}] -> {Null_|List_}
  74[017] - load local 3
- 75[078] - invoke at // {*}
- 76[061] - invoke virtual set a1 // {*}
- 79[010] - pop, load field local 21 // {Null_|Packet}
+ 75[078] - invoke at // [{Null_|List_}, {*}] -> {*}
+ 76[061] - invoke virtual set a1 // [{Null_|Packet}, {*}] -> {*}
+ 79[010] - pop, load field local 21 // [{HandlerTask}] -> {Null_|Packet}
  81[016] - load local 2
  82[025] - load smi 1
- 83[073] - invoke add // {float|LargeInteger_|SmallInteger_}
- 84[061] - invoke virtual set a1 // {float|LargeInteger_|SmallInteger_}
- 87[010] - pop, load field local 5 // {Null_|Scheduler}
+ 83[073] - invoke add // [{*}, {SmallInteger_}] -> {float|LargeInteger_|SmallInteger_}
+ 84[061] - invoke virtual set a1 // [{Null_|Packet}, {float|LargeInteger_|SmallInteger_}] -> {float|LargeInteger_|SmallInteger_}
+ 87[010] - pop, load field local 5 // [{HandlerTask}] -> {Null_|Scheduler}
  89[015] - load local 1
- 90[053] - invoke static Scheduler.queue tests/type_propagation/richards_test.toit // {*}
+ 90[053] - invoke static Scheduler.queue tests/type_propagation/richards_test.toit // [{Null_|Scheduler}, {Null_|Packet}] -> {*}
  93[088] - return S3 2
  96[080] - branch T118
- 99[009] - load field local 20 // {Null_|Packet}
+ 99[009] - load field local 20 // [{HandlerTask}] -> {Null_|Packet}
 101[019] - load local 5
-102[009] - load field local 22 // {Null_|Packet}
-104[060] - invoke virtual get link // {Null_|Packet}
+102[009] - load field local 22 // [{HandlerTask}] -> {Null_|Packet}
+104[060] - invoke virtual get link // [{Null_|Packet}] -> {Null_|Packet}
 107[013] - store field, pop 1
-109[009] - load field local 5 // {Null_|Scheduler}
+109[009] - load field local 5 // [{HandlerTask}] -> {Null_|Scheduler}
 111[015] - load local 1
-112[053] - invoke static Scheduler.queue tests/type_propagation/richards_test.toit // {*}
+112[053] - invoke static Scheduler.queue tests/type_propagation/richards_test.toit // [{Null_|Scheduler}, {Null_|Packet}] -> {*}
 115[088] - return S3 2
 118[041] - pop 1
-119[009] - load field local 3 // {Null_|Scheduler}
-121[053] - invoke static Scheduler.suspend_current tests/type_propagation/richards_test.toit // {*}
+119[009] - load field local 3 // [{HandlerTask}] -> {Null_|Scheduler}
+121[053] - invoke static Scheduler.suspend_current tests/type_propagation/richards_test.toit // [{Null_|Scheduler}] -> {*}
 124[088] - return S1 2
 
 Packet tests/type_propagation/richards_test.toit
@@ -827,14 +827,14 @@ Packet tests/type_propagation/richards_test.toit
  22[019] - load local 5
  23[026] - load smi 4
  25[022] - load null
- 26[053] - invoke static List <sdk>/core/collections.toit // {List_}
+ 26[053] - invoke static List <sdk>/core/collections.toit // [{SmallInteger_}, {Null_}] -> {List_}
  29[013] - store field, pop 4
  31[019] - load local 5
  32[088] - return S1 4
 
 Packet.link tests/type_propagation/richards_test.toit
  - argument 0: {Packet}
-  0[009] - load field local 2 // {Null_|Packet}
+  0[009] - load field local 2 // [{Packet}] -> {Null_|Packet}
   2[088] - return S1 1
 
 Packet.link= tests/type_propagation/richards_test.toit
@@ -849,7 +849,7 @@ Packet.link= tests/type_propagation/richards_test.toit
 
 Packet.id tests/type_propagation/richards_test.toit
  - argument 0: {Packet}
-  0[009] - load field local 18 // {Null_|LargeInteger_|SmallInteger_}
+  0[009] - load field local 18 // [{Packet}] -> {Null_|LargeInteger_|SmallInteger_}
   2[088] - return S1 1
 
 Packet.id= tests/type_propagation/richards_test.toit
@@ -863,12 +863,12 @@ Packet.id= tests/type_propagation/richards_test.toit
 
 Packet.kind tests/type_propagation/richards_test.toit
  - argument 0: {Packet}
-  0[009] - load field local 34 // {Null_|SmallInteger_}
+  0[009] - load field local 34 // [{Packet}] -> {Null_|SmallInteger_}
   2[088] - return S1 1
 
 Packet.a1 tests/type_propagation/richards_test.toit
  - argument 0: {Packet}
-  0[009] - load field local 50 // {*}
+  0[009] - load field local 50 // [{Packet}] -> {*}
   2[088] - return S1 1
 
 Packet.a1= tests/type_propagation/richards_test.toit
@@ -881,7 +881,7 @@ Packet.a1= tests/type_propagation/richards_test.toit
 
 Packet.a2 tests/type_propagation/richards_test.toit
  - argument 0: {Packet}
-  0[009] - load field local 66 // {Null_|List_}
+  0[009] - load field local 66 // [{Packet}] -> {Null_|List_}
   2[088] - return S1 1
 
 Packet.add_to tests/type_propagation/richards_test.toit
@@ -897,7 +897,7 @@ Packet.add_to tests/type_propagation/richards_test.toit
  11[088] - return S1 2
  14[016] - load local 2
  15[014] - load local 0
- 16[060] - invoke virtual get link // {Null_|Packet}
+ 16[060] - invoke virtual get link // [{Null_|Packet}] -> {Null_|Packet}
  19[014] - load local 0
  20[081] - branch if true T27
  23[041] - pop 1
@@ -908,6 +908,6 @@ Packet.add_to tests/type_propagation/richards_test.toit
  31[083] - branch back T15
  36[014] - load local 0
  37[019] - load local 5
- 38[061] - invoke virtual set link // {Packet}
+ 38[061] - invoke virtual set link // [{Null_|Packet}, {Packet}] -> {Packet}
  41[002] - pop, load local S3
  43[088] - return S2 2
diff --git a/tests/type_propagation/gold/richards_test.gold-O2 b/tests/type_propagation/gold/richards_test.gold-O2
index 14924b859..e72f2961a 100644
--- a/tests/type_propagation/gold/richards_test.gold-O2
+++ b/tests/type_propagation/gold/richards_test.gold-O2
@@ -4,116 +4,116 @@ main tests/type_propagation/richards_test.toit
 
 run_richards tests/type_propagation/richards_test.toit
   0[042] - allocate instance Scheduler
-  2[053] - invoke static Scheduler tests/type_propagation/richards_test.toit // {Scheduler}
+  2[053] - invoke static Scheduler tests/type_propagation/richards_test.toit // [{Scheduler}] -> {Scheduler}
   5[014] - load local 0
   6[023] - load smi 0
   7[023] - load smi 0
   8[022] - load null
   9[027] - load smi 10000
- 12[053] - invoke static Scheduler.add_idle_task tests/type_propagation/richards_test.toit // {Null_}
+ 12[053] - invoke static Scheduler.add_idle_task tests/type_propagation/richards_test.toit // [{Scheduler}, {SmallInteger_}, {SmallInteger_}, {Null_}, {SmallInteger_}] -> {Null_}
  15[041] - pop 1
  16[042] - allocate instance Packet
  18[022] - load null
  19[025] - load smi 1
  20[025] - load smi 1
- 21[053] - invoke static Packet tests/type_propagation/richards_test.toit // {Packet}
+ 21[053] - invoke static Packet tests/type_propagation/richards_test.toit // [{Packet}, {Null_}, {SmallInteger_}, {SmallInteger_}] -> {Packet}
  24[042] - allocate instance Packet
  26[015] - load local 1
  27[025] - load smi 1
  28[025] - load smi 1
- 29[053] - invoke static Packet tests/type_propagation/richards_test.toit // {Packet}
+ 29[053] - invoke static Packet tests/type_propagation/richards_test.toit // [{Packet}, {Packet}, {SmallInteger_}, {SmallInteger_}] -> {Packet}
  32[004] - store local, pop S1
  34[015] - load local 1
  35[025] - load smi 1
  36[027] - load smi 1000
  39[017] - load local 3
- 40[053] - invoke static Scheduler.add_worker_task tests/type_propagation/richards_test.toit // {Null_}
+ 40[053] - invoke static Scheduler.add_worker_task tests/type_propagation/richards_test.toit // [{Scheduler}, {SmallInteger_}, {SmallInteger_}, {Packet}] -> {Null_}
  43[041] - pop 1
  44[042] - allocate instance Packet
  46[022] - load null
  47[026] - load smi 4
  49[023] - load smi 0
- 50[053] - invoke static Packet tests/type_propagation/richards_test.toit // {Packet}
+ 50[053] - invoke static Packet tests/type_propagation/richards_test.toit // [{Packet}, {Null_}, {SmallInteger_}, {SmallInteger_}] -> {Packet}
  53[004] - store local, pop S1
  55[042] - allocate instance Packet
  57[015] - load local 1
  58[026] - load smi 4
  60[023] - load smi 0
- 61[053] - invoke static Packet tests/type_propagation/richards_test.toit // {Packet}
+ 61[053] - invoke static Packet tests/type_propagation/richards_test.toit // [{Packet}, {Packet}, {SmallInteger_}, {SmallInteger_}] -> {Packet}
  64[004] - store local, pop S1
  66[042] - allocate instance Packet
  68[015] - load local 1
  69[026] - load smi 4
  71[023] - load smi 0
- 72[053] - invoke static Packet tests/type_propagation/richards_test.toit // {Packet}
+ 72[053] - invoke static Packet tests/type_propagation/richards_test.toit // [{Packet}, {Packet}, {SmallInteger_}, {SmallInteger_}] -> {Packet}
  75[004] - store local, pop S1
  77[015] - load local 1
  78[026] - load smi 2
  80[027] - load smi 2000
  83[017] - load local 3
- 84[053] - invoke static Scheduler.add_handler_task tests/type_propagation/richards_test.toit // {Null_}
+ 84[053] - invoke static Scheduler.add_handler_task tests/type_propagation/richards_test.toit // [{Scheduler}, {SmallInteger_}, {SmallInteger_}, {Packet}] -> {Null_}
  87[041] - pop 1
  88[042] - allocate instance Packet
  90[022] - load null
  91[026] - load smi 5
  93[023] - load smi 0
- 94[053] - invoke static Packet tests/type_propagation/richards_test.toit // {Packet}
+ 94[053] - invoke static Packet tests/type_propagation/richards_test.toit // [{Packet}, {Null_}, {SmallInteger_}, {SmallInteger_}] -> {Packet}
  97[004] - store local, pop S1
  99[042] - allocate instance Packet
 101[015] - load local 1
 102[026] - load smi 5
 104[023] - load smi 0
-105[053] - invoke static Packet tests/type_propagation/richards_test.toit // {Packet}
+105[053] - invoke static Packet tests/type_propagation/richards_test.toit // [{Packet}, {Packet}, {SmallInteger_}, {SmallInteger_}] -> {Packet}
 108[004] - store local, pop S1
 110[042] - allocate instance Packet
 112[015] - load local 1
 113[026] - load smi 5
 115[023] - load smi 0
-116[053] - invoke static Packet tests/type_propagation/richards_test.toit // {Packet}
+116[053] - invoke static Packet tests/type_propagation/richards_test.toit // [{Packet}, {Packet}, {SmallInteger_}, {SmallInteger_}] -> {Packet}
 119[004] - store local, pop S1
 121[015] - load local 1
 122[026] - load smi 3
 124[027] - load smi 3000
 127[017] - load local 3
-128[053] - invoke static Scheduler.add_handler_task tests/type_propagation/richards_test.toit // {Null_}
+128[053] - invoke static Scheduler.add_handler_task tests/type_propagation/richards_test.toit // [{Scheduler}, {SmallInteger_}, {SmallInteger_}, {Packet}] -> {Null_}
 131[002] - pop, load local S1
 133[026] - load smi 4
 135[027] - load smi 4000
 138[022] - load null
-139[053] - invoke static Scheduler.add_device_task tests/type_propagation/richards_test.toit // {Null_}
+139[053] - invoke static Scheduler.add_device_task tests/type_propagation/richards_test.toit // [{Scheduler}, {SmallInteger_}, {SmallInteger_}, {Null_}] -> {Null_}
 142[002] - pop, load local S1
 144[026] - load smi 5
 146[027] - load smi 5000
 149[022] - load null
-150[053] - invoke static Scheduler.add_device_task tests/type_propagation/richards_test.toit // {Null_}
+150[053] - invoke static Scheduler.add_device_task tests/type_propagation/richards_test.toit // [{Scheduler}, {SmallInteger_}, {SmallInteger_}, {Null_}] -> {Null_}
 153[002] - pop, load local S1
-155[053] - invoke static Scheduler.schedule tests/type_propagation/richards_test.toit // {Null_}
+155[053] - invoke static Scheduler.schedule tests/type_propagation/richards_test.toit // [{Scheduler}] -> {Null_}
 158[041] - pop 1
 159[029] - load [block] in run_richards tests/type_propagation/richards_test.toit
 164[038] - load block 0
-166[053] - invoke static assert_ <sdk>/core/assert_.toit // {Null_}
+166[053] - invoke static assert_ <sdk>/core/assert_.toit // [[block]] -> {Null_}
 169[040] - pop 2
 171[029] - load [block] in run_richards tests/type_propagation/richards_test.toit
 176[038] - load block 0
-178[053] - invoke static assert_ <sdk>/core/assert_.toit // {Null_}
+178[053] - invoke static assert_ <sdk>/core/assert_.toit // [[block]] -> {Null_}
 181[089] - return null S4 0
 
 [block] in run_richards tests/type_propagation/richards_test.toit
  - argument 0: [block]
   0[016] - load local 2
   1[005] - load outer S2 // {Scheduler}
-  3[007] - load field 0 // {Null_|LargeInteger_|SmallInteger_}
+  3[007] - load field 0 // [{Scheduler}] -> {Null_|LargeInteger_|SmallInteger_}
   5[027] - load smi 23246
-  8[062] - invoke eq // {True_|False_}
+  8[062] - invoke eq // [{Null_|LargeInteger_|SmallInteger_}, {SmallInteger_}] -> {True_|False_}
   9[088] - return S1 1
 
 [block] in run_richards tests/type_propagation/richards_test.toit
  - argument 0: [block]
   0[016] - load local 2
   1[005] - load outer S2 // {Scheduler}
-  3[007] - load field 1 // {Null_|LargeInteger_|SmallInteger_}
+  3[007] - load field 1 // [{Scheduler}] -> {Null_|LargeInteger_|SmallInteger_}
   5[027] - load smi 9297
-  8[062] - invoke eq // {True_|False_}
+  8[062] - invoke eq // [{Null_|LargeInteger_|SmallInteger_}, {SmallInteger_}] -> {True_|False_}
   9[088] - return S1 1
 
 Scheduler tests/type_propagation/richards_test.toit
@@ -127,7 +127,7 @@ Scheduler tests/type_propagation/richards_test.toit
   8[016] - load local 2
   9[026] - load smi 6
  11[022] - load null
- 12[053] - invoke static List <sdk>/core/collections.toit // {List_}
+ 12[053] - invoke static List <sdk>/core/collections.toit // [{SmallInteger_}, {Null_}] -> {List_}
  15[013] - store field, pop 2
  17[016] - load local 2
  18[088] - return S1 1
@@ -146,8 +146,8 @@ Scheduler.add_idle_task tests/type_propagation/richards_test.toit
  10[000] - load local S11
  12[025] - load smi 1
  13[000] - load local S9
- 15[053] - invoke static IdleTask tests/type_propagation/richards_test.toit // {IdleTask}
- 18[053] - invoke static Scheduler.add_running_task tests/type_propagation/richards_test.toit // {Null_}
+ 15[053] - invoke static IdleTask tests/type_propagation/richards_test.toit // [{IdleTask}, {Scheduler}, {SmallInteger_}, {SmallInteger_}] -> {IdleTask}
+ 18[053] - invoke static Scheduler.add_running_task tests/type_propagation/richards_test.toit // [{Scheduler}, {SmallInteger_}, {SmallInteger_}, {Null_}, {IdleTask}] -> {Null_}
  21[089] - return null S1 5
 
 Scheduler.add_worker_task tests/type_propagation/richards_test.toit
@@ -163,8 +163,8 @@ Scheduler.add_worker_task tests/type_propagation/richards_test.toit
   6[000] - load local S10
   8[026] - load smi 2
  10[023] - load smi 0
- 11[053] - invoke static WorkerTask tests/type_propagation/richards_test.toit // {WorkerTask}
- 14[053] - invoke static Scheduler.add_task tests/type_propagation/richards_test.toit // {Null_}
+ 11[053] - invoke static WorkerTask tests/type_propagation/richards_test.toit // [{WorkerTask}, {Scheduler}, {SmallInteger_}, {SmallInteger_}] -> {WorkerTask}
+ 14[053] - invoke static Scheduler.add_task tests/type_propagation/richards_test.toit // [{Scheduler}, {SmallInteger_}, {SmallInteger_}, {Packet}, {WorkerTask}] -> {Null_}
  17[089] - return null S1 4
 
 Scheduler.add_handler_task tests/type_propagation/richards_test.toit
@@ -178,8 +178,8 @@ Scheduler.add_handler_task tests/type_propagation/richards_test.toit
   3[019] - load local 5
   4[042] - allocate instance HandlerTask
   6[000] - load local S10
-  8[053] - invoke static HandlerTask tests/type_propagation/richards_test.toit // {HandlerTask}
- 11[053] - invoke static Scheduler.add_task tests/type_propagation/richards_test.toit // {Null_}
+  8[053] - invoke static HandlerTask tests/type_propagation/richards_test.toit // [{HandlerTask}, {Scheduler}] -> {HandlerTask}
+ 11[053] - invoke static Scheduler.add_task tests/type_propagation/richards_test.toit // [{Scheduler}, {SmallInteger_}, {SmallInteger_}, {Packet}, {HandlerTask}] -> {Null_}
  14[089] - return null S1 4
 
 Scheduler.add_device_task tests/type_propagation/richards_test.toit
@@ -193,8 +193,8 @@ Scheduler.add_device_task tests/type_propagation/richards_test.toit
   3[019] - load local 5
   4[042] - allocate instance DeviceTask
   6[000] - load local S10
-  8[053] - invoke static DeviceTask tests/type_propagation/richards_test.toit // {DeviceTask}
- 11[053] - invoke static Scheduler.add_task tests/type_propagation/richards_test.toit // {Null_}
+  8[053] - invoke static DeviceTask tests/type_propagation/richards_test.toit // [{DeviceTask}, {Scheduler}] -> {DeviceTask}
+ 11[053] - invoke static Scheduler.add_task tests/type_propagation/richards_test.toit // [{Scheduler}, {SmallInteger_}, {SmallInteger_}, {Null_}, {DeviceTask}] -> {Null_}
  14[089] - return null S1 4
 
 Scheduler.add_running_task tests/type_propagation/richards_test.toit
@@ -208,9 +208,9 @@ Scheduler.add_running_task tests/type_propagation/richards_test.toit
   4[000] - load local S6
   6[000] - load local S6
   8[000] - load local S6
- 10[053] - invoke static Scheduler.add_task tests/type_propagation/richards_test.toit // {Null_}
- 13[010] - pop, load field local 70 // {*}
- 15[058] - invoke virtual set_running // {Null_}
+ 10[053] - invoke static Scheduler.add_task tests/type_propagation/richards_test.toit // [{Scheduler}, {SmallInteger_}, {SmallInteger_}, {Null_}, {IdleTask}] -> {Null_}
+ 13[010] - pop, load field local 70 // [{Scheduler}] -> {*}
+ 15[058] - invoke virtual set_running // [{*}] -> {Null_}
  19[089] - return null S1 5
 
 Scheduler.add_task tests/type_propagation/richards_test.toit
@@ -221,141 +221,141 @@ Scheduler.add_task tests/type_propagation/richards_test.toit
  - argument 4: {HandlerTask|WorkerTask|DeviceTask|IdleTask}
   0[000] - load local S6
   2[042] - allocate instance TaskControlBlock
-  4[009] - load field local 56 // {*}
+  4[009] - load field local 56 // [{Scheduler}] -> {*}
   6[000] - load local S8
   8[000] - load local S8
  10[000] - load local S8
  12[000] - load local S8
- 14[053] - invoke static TaskControlBlock tests/type_propagation/richards_test.toit // {TaskControlBlock}
+ 14[053] - invoke static TaskControlBlock tests/type_propagation/richards_test.toit // [{TaskControlBlock}, {*}, {SmallInteger_}, {SmallInteger_}, {Null_|Packet}, {HandlerTask|WorkerTask|DeviceTask|IdleTask}] -> {TaskControlBlock}
  17[013] - store field, pop 4
  19[000] - load local S6
- 21[009] - load field local 71 // {*}
+ 21[009] - load field local 71 // [{Scheduler}] -> {*}
  23[013] - store field, pop 3
- 25[009] - load field local 38 // {Null_|List_}
+ 25[009] - load field local 38 // [{Scheduler}] -> {Null_|List_}
  27[000] - load local S6
- 29[009] - load field local 72 // {*}
- 31[079] - invoke at_put // {*}
+ 29[009] - load field local 72 // [{Scheduler}] -> {*}
+ 31[079] - invoke at_put // [{Null_|List_}, {SmallInteger_}, {*}] -> {*}
  32[089] - return null S1 5
 
 Scheduler.schedule tests/type_propagation/richards_test.toit
  - argument 0: {Scheduler}
   0[016] - load local 2
-  1[009] - load field local 51 // {*}
+  1[009] - load field local 51 // [{Scheduler}] -> {*}
   3[013] - store field, pop 4
-  5[009] - load field local 66 // {*}
+  5[009] - load field local 66 // [{Scheduler}] -> {*}
   7[082] - branch if false T52
- 10[009] - load field local 66 // {*}
- 12[058] - invoke virtual is_held_or_suspended // {True_|False_}
+ 10[009] - load field local 66 // [{Scheduler}] -> {*}
+ 12[058] - invoke virtual is_held_or_suspended // [{*}] -> {True_|False_}
  16[082] - branch if false T30
  19[016] - load local 2
- 20[009] - load field local 67 // {*}
- 22[060] - invoke virtual get link // {Null_|Packet|TaskControlBlock}
+ 20[009] - load field local 67 // [{Scheduler}] -> {*}
+ 22[060] - invoke virtual get link // [{*}] -> {Null_|Packet|TaskControlBlock}
  25[013] - store field, pop 4
  27[080] - branch T47
  30[016] - load local 2
- 31[009] - load field local 67 // {*}
- 33[060] - invoke virtual get id // {Null_|LargeInteger_|SmallInteger_|ByteArray_}
+ 31[009] - load field local 67 // [{Scheduler}] -> {*}
+ 33[060] - invoke virtual get id // [{*}] -> {Null_|LargeInteger_|SmallInteger_|ByteArray_}
  36[013] - store field, pop 5
  38[016] - load local 2
- 39[009] - load field local 67 // {*}
- 41[058] - invoke virtual run // {*}
+ 39[009] - load field local 67 // [{Scheduler}] -> {*}
+ 41[058] - invoke virtual run // [{*}] -> {*}
  45[013] - store field, pop 4
  47[083] - branch back T5
  52[089] - return null S0 1
 
 Scheduler.hold_current tests/type_propagation/richards_test.toit
  - argument 0: {Scheduler}
-  0[009] - load field local 18 // {Null_|LargeInteger_|SmallInteger_}
+  0[009] - load field local 18 // [{Scheduler}] -> {Null_|LargeInteger_|SmallInteger_}
   2[017] - load local 3
   3[015] - load local 1
   4[025] - load smi 1
-  5[073] - invoke add // {LargeInteger_|SmallInteger_}
+  5[073] - invoke add // [{Null_|LargeInteger_|SmallInteger_}, {SmallInteger_}] -> {LargeInteger_|SmallInteger_}
   6[013] - store field, pop 1
-  8[010] - pop, load field local 66 // {*}
- 10[058] - invoke virtual mark_as_held // {Null_}
- 14[010] - pop, load field local 66 // {*}
- 16[060] - invoke virtual get link // {Null_|Packet|TaskControlBlock}
+  8[010] - pop, load field local 66 // [{Scheduler}] -> {*}
+ 10[058] - invoke virtual mark_as_held // [{*}] -> {Null_}
+ 14[010] - pop, load field local 66 // [{Scheduler}] -> {*}
+ 16[060] - invoke virtual get link // [{*}] -> {Null_|Packet|TaskControlBlock}
  19[088] - return S1 1
 
 Scheduler.suspend_current tests/type_propagation/richards_test.toit
  - argument 0: {Scheduler}
-  0[009] - load field local 66 // {*}
-  2[058] - invoke virtual mark_as_suspended // {Null_}
-  6[010] - pop, load field local 66 // {*}
+  0[009] - load field local 66 // [{Scheduler}] -> {*}
+  2[058] - invoke virtual mark_as_suspended // [{*}] -> {Null_}
+  6[010] - pop, load field local 66 // [{Scheduler}] -> {*}
   8[088] - return S1 1
 
 Scheduler.release tests/type_propagation/richards_test.toit
  - argument 0: {Scheduler}
  - argument 1: {SmallInteger_}
-  0[009] - load field local 35 // {Null_|List_}
+  0[009] - load field local 35 // [{Scheduler}] -> {Null_|List_}
   2[017] - load local 3
-  3[078] - invoke at // {*}
+  3[078] - invoke at // [{Null_|List_}, {SmallInteger_}] -> {*}
   4[014] - load local 0
   5[081] - branch if true T12
   8[014] - load local 0
   9[088] - return S2 2
  12[014] - load local 0
- 13[058] - invoke virtual mark_as_not_held // {Null_}
+ 13[058] - invoke virtual mark_as_not_held // [{*}] -> {Null_}
  17[002] - pop, load local S0
- 19[060] - invoke virtual get priority // {Null_|SmallInteger_}
- 22[009] - load field local 69 // {*}
- 24[060] - invoke virtual get priority // {Null_|SmallInteger_}
- 27[064] - invoke gt // {True_|False_}
+ 19[060] - invoke virtual get priority // [{*}] -> {Null_|SmallInteger_}
+ 22[009] - load field local 69 // [{Scheduler}] -> {*}
+ 24[060] - invoke virtual get priority // [{*}] -> {Null_|SmallInteger_}
+ 27[064] - invoke gt // [{Null_|SmallInteger_}, {Null_|SmallInteger_}] -> {True_|False_}
  28[082] - branch if false T38
  31[014] - load local 0
  32[088] - return S2 2
  35[080] - branch T43
- 38[009] - load field local 68 // {*}
+ 38[009] - load field local 68 // [{Scheduler}] -> {*}
  40[088] - return S2 2
 
 Scheduler.queue tests/type_propagation/richards_test.toit
  - argument 0: {Scheduler}
  - argument 1: {Null_|Packet}
   0[052] - load local, as class, pop 2 - Packet(35 - 36) // {True_|False_}
-  2[009] - load field local 35 // {Null_|List_}
-  4[009] - load field local 19 // {Null_|LargeInteger_|SmallInteger_}
-  6[078] - invoke at // {*}
+  2[009] - load field local 35 // [{Scheduler}] -> {Null_|List_}
+  4[009] - load field local 19 // [{Packet}] -> {Null_|LargeInteger_|SmallInteger_}
+  6[078] - invoke at // [{Null_|List_}, {Null_|LargeInteger_|SmallInteger_}] -> {*}
   7[014] - load local 0
   8[081] - branch if true T15
  11[014] - load local 0
  12[088] - return S2 2
- 15[009] - load field local 4 // {Null_|LargeInteger_|SmallInteger_}
+ 15[009] - load field local 4 // [{Scheduler}] -> {Null_|LargeInteger_|SmallInteger_}
  17[019] - load local 5
  18[015] - load local 1
  19[025] - load smi 1
- 20[073] - invoke add // {LargeInteger_|SmallInteger_}
+ 20[073] - invoke add // [{Null_|LargeInteger_|SmallInteger_}, {SmallInteger_}] -> {LargeInteger_|SmallInteger_}
  21[013] - store field, pop 0
  23[002] - pop, load local S3
  25[022] - load null
  26[013] - store field, pop 0
  28[017] - load local 3
- 29[009] - load field local 85 // {Null_|LargeInteger_|SmallInteger_|ByteArray_}
+ 29[009] - load field local 85 // [{Scheduler}] -> {Null_|LargeInteger_|SmallInteger_|ByteArray_}
  31[048] - as class LargeInteger_(19 - 21) // {True_|False_}
  33[013] - store field, pop 1
  35[014] - load local 0
- 36[009] - load field local 69 // {*}
+ 36[009] - load field local 69 // [{Scheduler}] -> {*}
  38[019] - load local 5
- 39[058] - invoke virtual check_priority_add // {*}
+ 39[058] - invoke virtual check_priority_add // [{*}, {*}, {Packet}] -> {*}
  43[088] - return S2 2
 
 STATE_NOT_HELD tests/type_propagation/richards_test.toit
   0[026] - load smi 4
-  2[058] - invoke virtual ~ // {SmallInteger_}
+  2[058] - invoke virtual ~ // [{SmallInteger_}] -> {SmallInteger_}
   6[088] - return S1 0
 
 TaskControlBlock.link tests/type_propagation/richards_test.toit
  - argument 0: {TaskControlBlock}
-  0[009] - load field local 2 // {Null_|TaskControlBlock}
+  0[009] - load field local 2 // [{TaskControlBlock}] -> {Null_|TaskControlBlock}
   2[088] - return S1 1
 
 TaskControlBlock.id tests/type_propagation/richards_test.toit
  - argument 0: {TaskControlBlock}
-  0[009] - load field local 18 // {Null_|SmallInteger_}
+  0[009] - load field local 18 // [{TaskControlBlock}] -> {Null_|SmallInteger_}
   2[088] - return S1 1
 
 TaskControlBlock.priority tests/type_propagation/richards_test.toit
  - argument 0: {TaskControlBlock}
-  0[009] - load field local 34 // {Null_|SmallInteger_}
+  0[009] - load field local 34 // [{TaskControlBlock}] -> {Null_|SmallInteger_}
   2[088] - return S1 1
 
 TaskControlBlock tests/type_propagation/richards_test.toit
@@ -386,7 +386,7 @@ TaskControlBlock tests/type_propagation/richards_test.toit
  32[013] - store field, pop 5
  34[000] - load local S7
  36[026] - load smi 2
- 38[009] - load field local 57 // {Null_|Packet}
+ 38[009] - load field local 57 // [{TaskControlBlock}] -> {Null_|Packet}
  40[082] - branch if false T46
  43[041] - pop 1
  44[026] - load smi 3
@@ -404,105 +404,105 @@ TaskControlBlock.set_running tests/type_propagation/richards_test.toit
 TaskControlBlock.mark_as_not_held tests/type_propagation/richards_test.toit
  - argument 0: {TaskControlBlock}
   0[016] - load local 2
-  1[009] - load field local 83 // {Null_|LargeInteger_|SmallInteger_}
+  1[009] - load field local 83 // [{TaskControlBlock}] -> {Null_|LargeInteger_|SmallInteger_}
   3[033] - load global var lazy G0 // {SmallInteger_}
-  5[069] - invoke bit and // {LargeInteger_|SmallInteger_}
+  5[069] - invoke bit and // [{Null_|LargeInteger_|SmallInteger_}, {SmallInteger_}] -> {LargeInteger_|SmallInteger_}
   6[013] - store field, pop 5
   8[089] - return null S0 1
 
 TaskControlBlock.mark_as_held tests/type_propagation/richards_test.toit
  - argument 0: {TaskControlBlock}
   0[016] - load local 2
-  1[009] - load field local 83 // {Null_|LargeInteger_|SmallInteger_}
+  1[009] - load field local 83 // [{TaskControlBlock}] -> {Null_|LargeInteger_|SmallInteger_}
   3[026] - load smi 4
-  5[067] - invoke bit or // {LargeInteger_|SmallInteger_}
+  5[067] - invoke bit or // [{Null_|LargeInteger_|SmallInteger_}, {SmallInteger_}] -> {LargeInteger_|SmallInteger_}
   6[013] - store field, pop 5
   8[089] - return null S0 1
 
 TaskControlBlock.is_held_or_suspended tests/type_propagation/richards_test.toit
  - argument 0: {TaskControlBlock}
-  0[009] - load field local 82 // {Null_|LargeInteger_|SmallInteger_}
+  0[009] - load field local 82 // [{TaskControlBlock}] -> {Null_|LargeInteger_|SmallInteger_}
   2[026] - load smi 4
-  4[069] - invoke bit and // {LargeInteger_|SmallInteger_}
+  4[069] - invoke bit and // [{Null_|LargeInteger_|SmallInteger_}, {SmallInteger_}] -> {LargeInteger_|SmallInteger_}
   5[023] - load smi 0
-  6[062] - invoke eq // {True_|False_}
+  6[062] - invoke eq // [{LargeInteger_|SmallInteger_}, {SmallInteger_}] -> {True_|False_}
   7[081] - branch if true T15
  10[020] - load literal true
  12[080] - branch T17
  15[020] - load literal false
  17[014] - load local 0
  18[081] - branch if true T26
- 21[010] - pop, load field local 82 // {Null_|LargeInteger_|SmallInteger_}
+ 21[010] - pop, load field local 82 // [{TaskControlBlock}] -> {Null_|LargeInteger_|SmallInteger_}
  23[026] - load smi 2
- 25[062] - invoke eq // {True_|False_}
+ 25[062] - invoke eq // [{Null_|LargeInteger_|SmallInteger_}, {SmallInteger_}] -> {True_|False_}
  26[088] - return S1 1
 
 TaskControlBlock.mark_as_suspended tests/type_propagation/richards_test.toit
  - argument 0: {TaskControlBlock}
   0[016] - load local 2
-  1[009] - load field local 83 // {Null_|LargeInteger_|SmallInteger_}
+  1[009] - load field local 83 // [{TaskControlBlock}] -> {Null_|LargeInteger_|SmallInteger_}
   3[026] - load smi 2
-  5[067] - invoke bit or // {LargeInteger_|SmallInteger_}
+  5[067] - invoke bit or // [{Null_|LargeInteger_|SmallInteger_}, {SmallInteger_}] -> {LargeInteger_|SmallInteger_}
   6[013] - store field, pop 5
   8[089] - return null S0 1
 
 TaskControlBlock.mark_as_runnable tests/type_propagation/richards_test.toit
  - argument 0: {TaskControlBlock}
   0[016] - load local 2
-  1[009] - load field local 83 // {Null_|LargeInteger_|SmallInteger_}
+  1[009] - load field local 83 // [{TaskControlBlock}] -> {Null_|LargeInteger_|SmallInteger_}
   3[025] - load smi 1
-  4[067] - invoke bit or // {LargeInteger_|SmallInteger_}
+  4[067] - invoke bit or // [{Null_|LargeInteger_|SmallInteger_}, {SmallInteger_}] -> {LargeInteger_|SmallInteger_}
   5[013] - store field, pop 5
   7[089] - return null S0 1
 
 TaskControlBlock.run tests/type_propagation/richards_test.toit
  - argument 0: {TaskControlBlock}
   0[022] - load null
-  1[009] - load field local 83 // {Null_|LargeInteger_|SmallInteger_}
+  1[009] - load field local 83 // [{TaskControlBlock}] -> {Null_|LargeInteger_|SmallInteger_}
   3[026] - load smi 3
-  5[062] - invoke eq // {True_|False_}
+  5[062] - invoke eq // [{Null_|LargeInteger_|SmallInteger_}, {SmallInteger_}] -> {True_|False_}
   6[082] - branch if false T31
-  9[009] - load field local 51 // {Null_|Packet}
+  9[009] - load field local 51 // [{TaskControlBlock}] -> {Null_|Packet}
  11[004] - store local, pop S1
  13[017] - load local 3
  14[015] - load local 1
- 15[060] - invoke virtual get link // {Null_|Packet}
+ 15[060] - invoke virtual get link // [{Null_|Packet}] -> {Null_|Packet}
  18[013] - store field, pop 3
  20[017] - load local 3
  21[023] - load smi 0
- 22[009] - load field local 53 // {Null_|Packet}
+ 22[009] - load field local 53 // [{TaskControlBlock}] -> {Null_|Packet}
  24[082] - branch if false T29
  27[041] - pop 1
  28[025] - load smi 1
  29[013] - store field, pop 5
- 31[009] - load field local 67 // {Null_|HandlerTask|WorkerTask|DeviceTask|IdleTask}
+ 31[009] - load field local 67 // [{TaskControlBlock}] -> {Null_|HandlerTask|WorkerTask|DeviceTask|IdleTask}
  33[015] - load local 1
- 34[058] - invoke virtual run // {*}
+ 34[058] - invoke virtual run // [{Null_|HandlerTask|WorkerTask|DeviceTask|IdleTask}, {Null_|Packet}] -> {*}
  38[088] - return S2 1
 
 TaskControlBlock.check_priority_add tests/type_propagation/richards_test.toit
  - argument 0: {TaskControlBlock}
  - argument 1: {*}
  - argument 2: {Packet}
-  0[009] - load field local 52 // {Null_|Packet}
+  0[009] - load field local 52 // [{TaskControlBlock}] -> {Null_|Packet}
   2[081] - branch if true T30
   5[018] - load local 4
   6[017] - load local 3
   7[013] - store field, pop 3
   9[018] - load local 4
- 10[053] - invoke static TaskControlBlock.mark_as_runnable tests/type_propagation/richards_test.toit // {Null_}
- 13[010] - pop, load field local 36 // {Null_|SmallInteger_}
+ 10[053] - invoke static TaskControlBlock.mark_as_runnable tests/type_propagation/richards_test.toit // [{TaskControlBlock}] -> {Null_}
+ 13[010] - pop, load field local 36 // [{TaskControlBlock}] -> {Null_|SmallInteger_}
  15[018] - load local 4
- 16[060] - invoke virtual get priority // {Null_|SmallInteger_}
- 19[064] - invoke gt // {True_|False_}
+ 16[060] - invoke virtual get priority // [{*}] -> {Null_|SmallInteger_}
+ 19[064] - invoke gt // [{Null_|SmallInteger_}, {Null_|SmallInteger_}] -> {True_|False_}
  20[082] - branch if false T27
  23[018] - load local 4
  24[088] - return S1 3
  27[080] - branch T40
  30[018] - load local 4
  31[017] - load local 3
- 32[009] - load field local 54 // {Null_|Packet}
- 34[058] - invoke virtual add_to // {Packet}
+ 32[009] - load field local 54 // [{TaskControlBlock}] -> {Null_|Packet}
+ 34[058] - invoke virtual add_to // [{Packet}, {Null_|Packet}] -> {Packet}
  38[013] - store field, pop 3
  40[017] - load local 3
  41[088] - return S1 3
@@ -527,45 +527,45 @@ IdleTask tests/type_propagation/richards_test.toit
 IdleTask.run tests/type_propagation/richards_test.toit
  - argument 0: {IdleTask}
  - argument 1: {Null_|Packet}
-  0[009] - load field local 35 // {Null_|LargeInteger_|SmallInteger_}
+  0[009] - load field local 35 // [{IdleTask}] -> {Null_|LargeInteger_|SmallInteger_}
   2[018] - load local 4
   3[015] - load local 1
   4[025] - load smi 1
-  5[074] - invoke sub // {LargeInteger_|SmallInteger_}
+  5[074] - invoke sub // [{Null_|LargeInteger_|SmallInteger_}, {SmallInteger_}] -> {LargeInteger_|SmallInteger_}
   6[013] - store field, pop 2
-  8[010] - pop, load field local 35 // {Null_|LargeInteger_|SmallInteger_}
+  8[010] - pop, load field local 35 // [{IdleTask}] -> {Null_|LargeInteger_|SmallInteger_}
  10[023] - load smi 0
- 11[062] - invoke eq // {True_|False_}
+ 11[062] - invoke eq // [{Null_|LargeInteger_|SmallInteger_}, {SmallInteger_}] -> {True_|False_}
  12[082] - branch if false T23
- 15[009] - load field local 3 // {Null_|Scheduler}
- 17[053] - invoke static Scheduler.hold_current tests/type_propagation/richards_test.toit // {Null_|Packet|TaskControlBlock}
+ 15[009] - load field local 3 // [{IdleTask}] -> {Null_|Scheduler}
+ 17[053] - invoke static Scheduler.hold_current tests/type_propagation/richards_test.toit // [{Null_|Scheduler}] -> {Null_|Packet|TaskControlBlock}
  20[088] - return S1 2
- 23[009] - load field local 19 // {Null_|LargeInteger_|SmallInteger_}
+ 23[009] - load field local 19 // [{IdleTask}] -> {Null_|LargeInteger_|SmallInteger_}
  25[025] - load smi 1
- 26[069] - invoke bit and // {LargeInteger_|SmallInteger_}
+ 26[069] - invoke bit and // [{Null_|LargeInteger_|SmallInteger_}, {SmallInteger_}] -> {LargeInteger_|SmallInteger_}
  27[023] - load smi 0
- 28[062] - invoke eq // {True_|False_}
+ 28[062] - invoke eq // [{LargeInteger_|SmallInteger_}, {SmallInteger_}] -> {True_|False_}
  29[082] - branch if false T52
  32[017] - load local 3
- 33[009] - load field local 20 // {Null_|LargeInteger_|SmallInteger_}
+ 33[009] - load field local 20 // [{IdleTask}] -> {Null_|LargeInteger_|SmallInteger_}
  35[025] - load smi 1
- 36[071] - invoke bit shr // {LargeInteger_|SmallInteger_}
+ 36[071] - invoke bit shr // [{Null_|LargeInteger_|SmallInteger_}, {SmallInteger_}] -> {LargeInteger_|SmallInteger_}
  37[013] - store field, pop 1
- 39[009] - load field local 3 // {Null_|Scheduler}
+ 39[009] - load field local 3 // [{IdleTask}] -> {Null_|Scheduler}
  41[026] - load smi 4
- 43[053] - invoke static Scheduler.release tests/type_propagation/richards_test.toit // {*}
+ 43[053] - invoke static Scheduler.release tests/type_propagation/richards_test.toit // [{Null_|Scheduler}, {SmallInteger_}] -> {*}
  46[088] - return S1 2
  49[080] - branch T73
  52[017] - load local 3
- 53[009] - load field local 20 // {Null_|LargeInteger_|SmallInteger_}
+ 53[009] - load field local 20 // [{IdleTask}] -> {Null_|LargeInteger_|SmallInteger_}
  55[025] - load smi 1
- 56[071] - invoke bit shr // {LargeInteger_|SmallInteger_}
+ 56[071] - invoke bit shr // [{Null_|LargeInteger_|SmallInteger_}, {SmallInteger_}] -> {LargeInteger_|SmallInteger_}
  57[027] - load smi 53256
- 60[068] - invoke bit xor // {LargeInteger_|SmallInteger_}
+ 60[068] - invoke bit xor // [{LargeInteger_|SmallInteger_}, {SmallInteger_}] -> {LargeInteger_|SmallInteger_}
  61[013] - store field, pop 1
- 63[009] - load field local 3 // {Null_|Scheduler}
+ 63[009] - load field local 3 // [{IdleTask}] -> {Null_|Scheduler}
  65[026] - load smi 5
- 67[053] - invoke static Scheduler.release tests/type_propagation/richards_test.toit // {*}
+ 67[053] - invoke static Scheduler.release tests/type_propagation/richards_test.toit // [{Null_|Scheduler}, {SmallInteger_}] -> {*}
  70[088] - return S1 2
 
 DeviceTask tests/type_propagation/richards_test.toit
@@ -582,25 +582,25 @@ DeviceTask.run tests/type_propagation/richards_test.toit
  - argument 1: {Null_|Packet}
   0[016] - load local 2
   1[081] - branch if true T35
-  4[009] - load field local 19 // {Null_|Packet}
+  4[009] - load field local 19 // [{DeviceTask}] -> {Null_|Packet}
   6[081] - branch if true T17
-  9[009] - load field local 3 // {Null_|Scheduler}
- 11[053] - invoke static Scheduler.suspend_current tests/type_propagation/richards_test.toit // {*}
+  9[009] - load field local 3 // [{DeviceTask}] -> {Null_|Scheduler}
+ 11[053] - invoke static Scheduler.suspend_current tests/type_propagation/richards_test.toit // [{Null_|Scheduler}] -> {*}
  14[088] - return S1 2
- 17[009] - load field local 19 // {Null_|Packet}
+ 17[009] - load field local 19 // [{DeviceTask}] -> {Null_|Packet}
  19[018] - load local 4
  20[022] - load null
  21[013] - store field, pop 1
- 23[009] - load field local 4 // {Null_|Scheduler}
+ 23[009] - load field local 4 // [{DeviceTask}] -> {Null_|Scheduler}
  25[015] - load local 1
- 26[053] - invoke static Scheduler.queue tests/type_propagation/richards_test.toit // {*}
+ 26[053] - invoke static Scheduler.queue tests/type_propagation/richards_test.toit // [{Null_|Scheduler}, {Null_|Packet}] -> {*}
  29[088] - return S2 2
  32[080] - branch T47
  35[017] - load local 3
  36[017] - load local 3
  37[013] - store field, pop 1
- 39[009] - load field local 3 // {Null_|Scheduler}
- 41[053] - invoke static Scheduler.hold_current tests/type_propagation/richards_test.toit // {Null_|Packet|TaskControlBlock}
+ 39[009] - load field local 3 // [{DeviceTask}] -> {Null_|Scheduler}
+ 41[053] - invoke static Scheduler.hold_current tests/type_propagation/richards_test.toit // [{Null_|Scheduler}] -> {Null_|Packet|TaskControlBlock}
  44[088] - return S1 2
 
 WorkerTask tests/type_propagation/richards_test.toit
@@ -625,57 +625,57 @@ WorkerTask.run tests/type_propagation/richards_test.toit
  - argument 1: {Null_|Packet}
   0[016] - load local 2
   1[081] - branch if true T12
-  4[009] - load field local 3 // {Null_|Scheduler}
-  6[053] - invoke static Scheduler.suspend_current tests/type_propagation/richards_test.toit // {*}
+  4[009] - load field local 3 // [{WorkerTask}] -> {Null_|Scheduler}
+  6[053] - invoke static Scheduler.suspend_current tests/type_propagation/richards_test.toit // [{Null_|Scheduler}] -> {*}
   9[088] - return S1 2
  12[017] - load local 3
  13[026] - load smi 2
- 15[009] - load field local 21 // {Null_|SmallInteger_}
+ 15[009] - load field local 21 // [{WorkerTask}] -> {Null_|SmallInteger_}
  17[026] - load smi 2
- 19[062] - invoke eq // {True_|False_}
+ 19[062] - invoke eq // [{Null_|SmallInteger_}, {SmallInteger_}] -> {True_|False_}
  20[082] - branch if false T26
  23[041] - pop 1
  24[026] - load smi 3
  26[013] - store field, pop 1
  28[016] - load local 2
- 29[009] - load field local 20 // {Null_|SmallInteger_}
- 31[061] - invoke virtual set id // {SmallInteger_}
+ 29[009] - load field local 20 // [{WorkerTask}] -> {Null_|SmallInteger_}
+ 31[061] - invoke virtual set id // [{Null_|Packet}, {Null_|SmallInteger_}] -> {SmallInteger_}
  34[002] - pop, load local S2
  36[023] - load smi 0
- 37[061] - invoke virtual set a1 // {SmallInteger_}
+ 37[061] - invoke virtual set a1 // [{Packet}, {SmallInteger_}] -> {SmallInteger_}
  40[041] - pop 1
  41[023] - load smi 0
  42[014] - load local 0
  43[026] - load smi 4
- 45[063] - invoke lt // {True_|False_}
+ 45[063] - invoke lt // [{LargeInteger_|SmallInteger_}, {SmallInteger_}] -> {True_|False_}
  46[082] - branch if false T87
  49[018] - load local 4
- 50[009] - load field local 37 // {Null_|LargeInteger_|SmallInteger_}
+ 50[009] - load field local 37 // [{WorkerTask}] -> {Null_|LargeInteger_|SmallInteger_}
  52[025] - load smi 1
- 53[073] - invoke add // {LargeInteger_|SmallInteger_}
+ 53[073] - invoke add // [{Null_|LargeInteger_|SmallInteger_}, {SmallInteger_}] -> {LargeInteger_|SmallInteger_}
  54[011] - store field 2
  56[026] - load smi 26
- 58[064] - invoke gt // {True_|False_}
+ 58[064] - invoke gt // [{LargeInteger_|SmallInteger_}, {SmallInteger_}] -> {True_|False_}
  59[082] - branch if false T66
  62[018] - load local 4
  63[025] - load smi 1
  64[013] - store field, pop 2
  66[017] - load local 3
- 67[060] - invoke virtual get a2 // {Null_|List_}
+ 67[060] - invoke virtual get a2 // [{Packet}] -> {Null_|List_}
  70[015] - load local 1
- 71[009] - load field local 38 // {Null_|LargeInteger_|SmallInteger_}
- 73[079] - invoke at_put // {*}
+ 71[009] - load field local 38 // [{WorkerTask}] -> {Null_|LargeInteger_|SmallInteger_}
+ 73[079] - invoke at_put // [{Null_|List_}, {LargeInteger_|SmallInteger_}, {Null_|LargeInteger_|SmallInteger_}] -> {*}
  74[041] - pop 1
  75[014] - load local 0
  76[014] - load local 0
  77[025] - load smi 1
- 78[073] - invoke add // {LargeInteger_|SmallInteger_}
+ 78[073] - invoke add // [{LargeInteger_|SmallInteger_}, {SmallInteger_}] -> {LargeInteger_|SmallInteger_}
  79[004] - store local, pop S2
  81[041] - pop 1
  82[083] - branch back T42
- 87[010] - pop, load field local 3 // {Null_|Scheduler}
+ 87[010] - pop, load field local 3 // [{WorkerTask}] -> {Null_|Scheduler}
  89[017] - load local 3
- 90[053] - invoke static Scheduler.queue tests/type_propagation/richards_test.toit // {*}
+ 90[053] - invoke static Scheduler.queue tests/type_propagation/richards_test.toit // [{Null_|Scheduler}, {Packet}] -> {*}
  93[088] - return S1 2
 
 HandlerTask tests/type_propagation/richards_test.toit
@@ -693,64 +693,64 @@ HandlerTask.run tests/type_propagation/richards_test.toit
   0[016] - load local 2
   1[082] - branch if false T36
   4[016] - load local 2
-  5[060] - invoke virtual get kind // {Null_|SmallInteger_}
+  5[060] - invoke virtual get kind // [{Null_|Packet}] -> {Null_|SmallInteger_}
   8[025] - load smi 1
-  9[062] - invoke eq // {True_|False_}
+  9[062] - invoke eq // [{Null_|SmallInteger_}, {SmallInteger_}] -> {True_|False_}
  10[082] - branch if false T26
  13[017] - load local 3
  14[017] - load local 3
- 15[009] - load field local 21 // {Null_|Packet}
- 17[058] - invoke virtual add_to // {Packet}
+ 15[009] - load field local 21 // [{HandlerTask}] -> {Null_|Packet}
+ 17[058] - invoke virtual add_to // [{Packet}, {Null_|Packet}] -> {Packet}
  21[013] - store field, pop 1
  23[080] - branch T36
  26[017] - load local 3
  27[017] - load local 3
- 28[009] - load field local 37 // {Null_|Packet}
- 30[058] - invoke virtual add_to // {Packet}
+ 28[009] - load field local 37 // [{HandlerTask}] -> {Null_|Packet}
+ 30[058] - invoke virtual add_to // [{Packet}, {Null_|Packet}] -> {Packet}
  34[013] - store field, pop 2
- 36[009] - load field local 19 // {Null_|Packet}
+ 36[009] - load field local 19 // [{HandlerTask}] -> {Null_|Packet}
  38[082] - branch if false T119
- 41[009] - load field local 19 // {Null_|Packet}
- 43[060] - invoke virtual get a1 // {*}
+ 41[009] - load field local 19 // [{HandlerTask}] -> {Null_|Packet}
+ 43[060] - invoke virtual get a1 // [{Null_|Packet}] -> {*}
  46[014] - load local 0
  47[026] - load smi 4
- 49[063] - invoke lt // {True_|False_}
+ 49[063] - invoke lt // [{*}, {SmallInteger_}] -> {True_|False_}
  50[082] - branch if false T99
- 53[009] - load field local 36 // {Null_|Packet}
+ 53[009] - load field local 36 // [{HandlerTask}] -> {Null_|Packet}
  55[082] - branch if false T96
- 58[009] - load field local 36 // {Null_|Packet}
+ 58[009] - load field local 36 // [{HandlerTask}] -> {Null_|Packet}
  60[019] - load local 5
- 61[009] - load field local 38 // {Null_|Packet}
- 63[060] - invoke virtual get link // {Null_|Packet}
+ 61[009] - load field local 38 // [{HandlerTask}] -> {Null_|Packet}
+ 63[060] - invoke virtual get link // [{Null_|Packet}] -> {Null_|Packet}
  66[013] - store field, pop 2
  68[014] - load local 0
- 69[009] - load field local 22 // {Null_|Packet}
- 71[060] - invoke virtual get a2 // {Null_|List_}
+ 69[009] - load field local 22 // [{HandlerTask}] -> {Null_|Packet}
+ 71[060] - invoke virtual get a2 // [{Null_|Packet}] -> {Null_|List_}
  74[017] - load local 3
- 75[078] - invoke at // {*}
- 76[061] - invoke virtual set a1 // {*}
- 79[010] - pop, load field local 21 // {Null_|Packet}
+ 75[078] - invoke at // [{Null_|List_}, {*}] -> {*}
+ 76[061] - invoke virtual set a1 // [{Null_|Packet}, {*}] -> {*}
+ 79[010] - pop, load field local 21 // [{HandlerTask}] -> {Null_|Packet}
  81[016] - load local 2
  82[025] - load smi 1
- 83[073] - invoke add // {float|LargeInteger_|SmallInteger_}
- 84[061] - invoke virtual set a1 // {float|LargeInteger_|SmallInteger_}
- 87[010] - pop, load field local 5 // {Null_|Scheduler}
+ 83[073] - invoke add // [{*}, {SmallInteger_}] -> {float|LargeInteger_|SmallInteger_}
+ 84[061] - invoke virtual set a1 // [{Null_|Packet}, {float|LargeInteger_|SmallInteger_}] -> {float|LargeInteger_|SmallInteger_}
+ 87[010] - pop, load field local 5 // [{HandlerTask}] -> {Null_|Scheduler}
  89[015] - load local 1
- 90[053] - invoke static Scheduler.queue tests/type_propagation/richards_test.toit // {*}
+ 90[053] - invoke static Scheduler.queue tests/type_propagation/richards_test.toit // [{Null_|Scheduler}, {Null_|Packet}] -> {*}
  93[088] - return S3 2
  96[080] - branch T118
- 99[009] - load field local 20 // {Null_|Packet}
+ 99[009] - load field local 20 // [{HandlerTask}] -> {Null_|Packet}
 101[019] - load local 5
-102[009] - load field local 22 // {Null_|Packet}
-104[060] - invoke virtual get link // {Null_|Packet}
+102[009] - load field local 22 // [{HandlerTask}] -> {Null_|Packet}
+104[060] - invoke virtual get link // [{Null_|Packet}] -> {Null_|Packet}
 107[013] - store field, pop 1
-109[009] - load field local 5 // {Null_|Scheduler}
+109[009] - load field local 5 // [{HandlerTask}] -> {Null_|Scheduler}
 111[015] - load local 1
-112[053] - invoke static Scheduler.queue tests/type_propagation/richards_test.toit // {*}
+112[053] - invoke static Scheduler.queue tests/type_propagation/richards_test.toit // [{Null_|Scheduler}, {Null_|Packet}] -> {*}
 115[088] - return S3 2
 118[041] - pop 1
-119[009] - load field local 3 // {Null_|Scheduler}
-121[053] - invoke static Scheduler.suspend_current tests/type_propagation/richards_test.toit // {*}
+119[009] - load field local 3 // [{HandlerTask}] -> {Null_|Scheduler}
+121[053] - invoke static Scheduler.suspend_current tests/type_propagation/richards_test.toit // [{Null_|Scheduler}] -> {*}
 124[088] - return S1 2
 
 Packet tests/type_propagation/richards_test.toit
@@ -773,14 +773,14 @@ Packet tests/type_propagation/richards_test.toit
  16[019] - load local 5
  17[026] - load smi 4
  19[022] - load null
- 20[053] - invoke static List <sdk>/core/collections.toit // {List_}
+ 20[053] - invoke static List <sdk>/core/collections.toit // [{SmallInteger_}, {Null_}] -> {List_}
  23[013] - store field, pop 4
  25[019] - load local 5
  26[088] - return S1 4
 
 Packet.link tests/type_propagation/richards_test.toit
  - argument 0: {Packet}
-  0[009] - load field local 2 // {Null_|Packet}
+  0[009] - load field local 2 // [{Packet}] -> {Null_|Packet}
   2[088] - return S1 1
 
 Packet.link= tests/type_propagation/richards_test.toit
@@ -793,7 +793,7 @@ Packet.link= tests/type_propagation/richards_test.toit
 
 Packet.id tests/type_propagation/richards_test.toit
  - argument 0: {Packet}
-  0[009] - load field local 18 // {Null_|LargeInteger_|SmallInteger_}
+  0[009] - load field local 18 // [{Packet}] -> {Null_|LargeInteger_|SmallInteger_}
   2[088] - return S1 1
 
 Packet.id= tests/type_propagation/richards_test.toit
@@ -807,12 +807,12 @@ Packet.id= tests/type_propagation/richards_test.toit
 
 Packet.kind tests/type_propagation/richards_test.toit
  - argument 0: {Packet}
-  0[009] - load field local 34 // {Null_|SmallInteger_}
+  0[009] - load field local 34 // [{Packet}] -> {Null_|SmallInteger_}
   2[088] - return S1 1
 
 Packet.a1 tests/type_propagation/richards_test.toit
  - argument 0: {Packet}
-  0[009] - load field local 50 // {*}
+  0[009] - load field local 50 // [{Packet}] -> {*}
   2[088] - return S1 1
 
 Packet.a1= tests/type_propagation/richards_test.toit
@@ -825,7 +825,7 @@ Packet.a1= tests/type_propagation/richards_test.toit
 
 Packet.a2 tests/type_propagation/richards_test.toit
  - argument 0: {Packet}
-  0[009] - load field local 66 // {Null_|List_}
+  0[009] - load field local 66 // [{Packet}] -> {Null_|List_}
   2[088] - return S1 1
 
 Packet.add_to tests/type_propagation/richards_test.toit
@@ -840,7 +840,7 @@ Packet.add_to tests/type_propagation/richards_test.toit
   9[088] - return S1 2
  12[016] - load local 2
  13[014] - load local 0
- 14[060] - invoke virtual get link // {Null_|Packet}
+ 14[060] - invoke virtual get link // [{Null_|Packet}] -> {Null_|Packet}
  17[014] - load local 0
  18[081] - branch if true T25
  21[041] - pop 1
@@ -851,6 +851,6 @@ Packet.add_to tests/type_propagation/richards_test.toit
  29[083] - branch back T13
  34[014] - load local 0
  35[019] - load local 5
- 36[061] - invoke virtual set link // {Packet}
+ 36[061] - invoke virtual set link // [{Null_|Packet}, {Packet}] -> {Packet}
  39[002] - pop, load local S3
  41[088] - return S2 2
diff --git a/tests/type_propagation/gold/spawn_test.gold b/tests/type_propagation/gold/spawn_test.gold
index 40c2bed17..66baf4fd0 100644
--- a/tests/type_propagation/gold/spawn_test.gold
+++ b/tests/type_propagation/gold/spawn_test.gold
@@ -2,21 +2,21 @@ main tests/type_propagation/spawn_test.toit
   0[029] - load [lambda] in main tests/type_propagation/spawn_test.toit
   5[023] - load smi 0
   6[022] - load null
-  7[053] - invoke static Array_ <sdk>/core/collections.toit // {LargeArray_|SmallArray_}
+  7[053] - invoke static Array_ <sdk>/core/collections.toit // [{SmallInteger_}, {Null_}] -> {LargeArray_|SmallArray_}
  10[014] - load local 0
  11[004] - store local, pop S1
  13[023] - load smi 0
- 14[053] - invoke static lambda_ <sdk>/core/objects.toit // {Lambda}
+ 14[053] - invoke static lambda_ <sdk>/core/objects.toit // [{SmallInteger_}, {LargeArray_|SmallArray_}, {SmallInteger_}] -> {Lambda}
  17[022] - load null
- 18[053] - invoke static spawn <sdk>/core/process.toit // {Process_}
+ 18[053] - invoke static spawn <sdk>/core/process.toit // [{Lambda}, {Null_}] -> {Process_}
  21[041] - pop 1
  22[020] - load literal hest
- 24[053] - invoke static id tests/type_propagation/spawn_test.toit // {String_}
+ 24[053] - invoke static id tests/type_propagation/spawn_test.toit // [{String_}] -> {String_}
  27[089] - return null S1 0
 
 [lambda] in main tests/type_propagation/spawn_test.toit
   0[026] - load smi 7
-  2[053] - invoke static id tests/type_propagation/spawn_test.toit // {SmallInteger_}
+  2[053] - invoke static id tests/type_propagation/spawn_test.toit // [{SmallInteger_}] -> {SmallInteger_}
   5[088] - return S1 0
 
 id tests/type_propagation/spawn_test.toit
diff --git a/tests/type_propagation/gold/spawn_test.gold-O2 b/tests/type_propagation/gold/spawn_test.gold-O2
index 40c2bed17..66baf4fd0 100644
--- a/tests/type_propagation/gold/spawn_test.gold-O2
+++ b/tests/type_propagation/gold/spawn_test.gold-O2
@@ -2,21 +2,21 @@ main tests/type_propagation/spawn_test.toit
   0[029] - load [lambda] in main tests/type_propagation/spawn_test.toit
   5[023] - load smi 0
   6[022] - load null
-  7[053] - invoke static Array_ <sdk>/core/collections.toit // {LargeArray_|SmallArray_}
+  7[053] - invoke static Array_ <sdk>/core/collections.toit // [{SmallInteger_}, {Null_}] -> {LargeArray_|SmallArray_}
  10[014] - load local 0
  11[004] - store local, pop S1
  13[023] - load smi 0
- 14[053] - invoke static lambda_ <sdk>/core/objects.toit // {Lambda}
+ 14[053] - invoke static lambda_ <sdk>/core/objects.toit // [{SmallInteger_}, {LargeArray_|SmallArray_}, {SmallInteger_}] -> {Lambda}
  17[022] - load null
- 18[053] - invoke static spawn <sdk>/core/process.toit // {Process_}
+ 18[053] - invoke static spawn <sdk>/core/process.toit // [{Lambda}, {Null_}] -> {Process_}
  21[041] - pop 1
  22[020] - load literal hest
- 24[053] - invoke static id tests/type_propagation/spawn_test.toit // {String_}
+ 24[053] - invoke static id tests/type_propagation/spawn_test.toit // [{String_}] -> {String_}
  27[089] - return null S1 0
 
 [lambda] in main tests/type_propagation/spawn_test.toit
   0[026] - load smi 7
-  2[053] - invoke static id tests/type_propagation/spawn_test.toit // {SmallInteger_}
+  2[053] - invoke static id tests/type_propagation/spawn_test.toit // [{SmallInteger_}] -> {SmallInteger_}
   5[088] - return S1 0
 
 id tests/type_propagation/spawn_test.toit
diff --git a/tests/type_propagation/gold/try_test.gold b/tests/type_propagation/gold/try_test.gold
index 11f6f8daf..3d37f0458 100644
--- a/tests/type_propagation/gold/try_test.gold
+++ b/tests/type_propagation/gold/try_test.gold
@@ -11,7 +11,7 @@ nested tests/type_propagation/try_test.toit
   1[029] - load [block] in nested tests/type_propagation/try_test.toit
   6[094] - link try 0
   8[038] - load block 4
- 10[055] - invoke block S1 // {Null_}
+ 10[055] - invoke block S1 // [[block]] -> {Null_}
  12[041] - pop 1
  13[095] - unlink try 0
  15[018] - load local 4
@@ -25,7 +25,7 @@ nested tests/type_propagation/try_test.toit
   1[029] - load [block] in [block] in nested tests/type_propagation/try_test.toit
   6[094] - link try 0
   8[038] - load block 4
- 10[055] - invoke block S1 // {SmallInteger_}
+ 10[055] - invoke block S1 // [[block]] -> {SmallInteger_}
  12[041] - pop 1
  13[095] - unlink try 0
  15[000] - load local S7
diff --git a/tests/type_propagation/gold/try_test.gold-O2 b/tests/type_propagation/gold/try_test.gold-O2
index 11f6f8daf..3d37f0458 100644
--- a/tests/type_propagation/gold/try_test.gold-O2
+++ b/tests/type_propagation/gold/try_test.gold-O2
@@ -11,7 +11,7 @@ nested tests/type_propagation/try_test.toit
   1[029] - load [block] in nested tests/type_propagation/try_test.toit
   6[094] - link try 0
   8[038] - load block 4
- 10[055] - invoke block S1 // {Null_}
+ 10[055] - invoke block S1 // [[block]] -> {Null_}
  12[041] - pop 1
  13[095] - unlink try 0
  15[018] - load local 4
@@ -25,7 +25,7 @@ nested tests/type_propagation/try_test.toit
   1[029] - load [block] in [block] in nested tests/type_propagation/try_test.toit
   6[094] - link try 0
   8[038] - load block 4
- 10[055] - invoke block S1 // {SmallInteger_}
+ 10[055] - invoke block S1 // [[block]] -> {SmallInteger_}
  12[041] - pop 1
  13[095] - unlink try 0
  15[000] - load local S7
diff --git a/tests/type_propagation/gold/typecheck_test.gold b/tests/type_propagation/gold/typecheck_test.gold
index 208ae1c48..e9e89534c 100644
--- a/tests/type_propagation/gold/typecheck_test.gold
+++ b/tests/type_propagation/gold/typecheck_test.gold
@@ -8,34 +8,34 @@ main tests/type_propagation/typecheck_test.toit
 
 test_simple tests/type_propagation/typecheck_test.toit
   0[022] - load null
-  1[053] - invoke static is_int tests/type_propagation/typecheck_test.toit // {False_}
-  4[053] - invoke static id tests/type_propagation/typecheck_test.toit // {False_}
+  1[053] - invoke static is_int tests/type_propagation/typecheck_test.toit // [{Null_}] -> {False_}
+  4[053] - invoke static id tests/type_propagation/typecheck_test.toit // [{False_}] -> {False_}
   7[041] - pop 1
   8[026] - load smi 7
- 10[053] - invoke static is_int tests/type_propagation/typecheck_test.toit // {True_}
- 13[053] - invoke static id tests/type_propagation/typecheck_test.toit // {True_}
+ 10[053] - invoke static is_int tests/type_propagation/typecheck_test.toit // [{SmallInteger_}] -> {True_}
+ 13[053] - invoke static id tests/type_propagation/typecheck_test.toit // [{True_}] -> {True_}
  16[041] - pop 1
  17[020] - load literal 7.9000000000000003553
- 19[053] - invoke static is_int tests/type_propagation/typecheck_test.toit // {False_}
- 22[053] - invoke static id tests/type_propagation/typecheck_test.toit // {False_}
+ 19[053] - invoke static is_int tests/type_propagation/typecheck_test.toit // [{float}] -> {False_}
+ 22[053] - invoke static id tests/type_propagation/typecheck_test.toit // [{False_}] -> {False_}
  25[041] - pop 1
  26[020] - load literal kurt
- 28[053] - invoke static is_int tests/type_propagation/typecheck_test.toit // {False_}
- 31[053] - invoke static id tests/type_propagation/typecheck_test.toit // {False_}
+ 28[053] - invoke static is_int tests/type_propagation/typecheck_test.toit // [{String_}] -> {False_}
+ 31[053] - invoke static id tests/type_propagation/typecheck_test.toit // [{False_}] -> {False_}
  34[089] - return null S1 0
 
 test_any tests/type_propagation/typecheck_test.toit
   0[020] - load literal true
-  2[053] - invoke static id tests/type_propagation/typecheck_test.toit // {True_}
+  2[053] - invoke static id tests/type_propagation/typecheck_test.toit // [{True_}] -> {True_}
   5[041] - pop 1
   6[020] - load literal true
-  8[053] - invoke static id tests/type_propagation/typecheck_test.toit // {True_}
+  8[053] - invoke static id tests/type_propagation/typecheck_test.toit // [{True_}] -> {True_}
  11[041] - pop 1
  12[026] - load smi 7
- 14[053] - invoke static id tests/type_propagation/typecheck_test.toit // {SmallInteger_}
+ 14[053] - invoke static id tests/type_propagation/typecheck_test.toit // [{SmallInteger_}] -> {SmallInteger_}
  17[041] - pop 1
  18[020] - load literal hest
- 20[053] - invoke static id tests/type_propagation/typecheck_test.toit // {String_}
+ 20[053] - invoke static id tests/type_propagation/typecheck_test.toit // [{String_}] -> {String_}
  23[089] - return null S1 0
 
 test_throws tests/type_propagation/typecheck_test.toit
@@ -43,13 +43,13 @@ test_throws tests/type_propagation/typecheck_test.toit
   5[038] - load block 0
   7[022] - load null
   8[022] - load null
-  9[053] - invoke static catch <sdk>/core/exceptions.toit // {*}
+  9[053] - invoke static catch <sdk>/core/exceptions.toit // [[block], {Null_}, {Null_}] -> {*}
  12[040] - pop 2
  14[029] - load [block] in test_throws tests/type_propagation/typecheck_test.toit
  19[038] - load block 0
  21[022] - load null
  22[022] - load null
- 23[053] - invoke static catch <sdk>/core/exceptions.toit // {*}
+ 23[053] - invoke static catch <sdk>/core/exceptions.toit // [[block], {Null_}, {Null_}] -> {*}
  26[089] - return null S2 0
 
 [block] in test_throws tests/type_propagation/typecheck_test.toit
@@ -61,7 +61,7 @@ test_throws tests/type_propagation/typecheck_test.toit
 [block] in test_throws tests/type_propagation/typecheck_test.toit
  - argument 0: [block]
   0[026] - load smi 7
-  2[053] - invoke static bar tests/type_propagation/typecheck_test.toit // {}
+  2[053] - invoke static bar tests/type_propagation/typecheck_test.toit // [{SmallInteger_}] -> {}
   5[088] - return S1 1
 
 foo tests/type_propagation/typecheck_test.toit
diff --git a/tests/type_propagation/gold/typecheck_test.gold-O2 b/tests/type_propagation/gold/typecheck_test.gold-O2
index eb720ba13..a13318b7b 100644
--- a/tests/type_propagation/gold/typecheck_test.gold-O2
+++ b/tests/type_propagation/gold/typecheck_test.gold-O2
@@ -8,34 +8,34 @@ main tests/type_propagation/typecheck_test.toit
 
 test_simple tests/type_propagation/typecheck_test.toit
   0[022] - load null
-  1[053] - invoke static is_int tests/type_propagation/typecheck_test.toit // {False_}
-  4[053] - invoke static id tests/type_propagation/typecheck_test.toit // {False_}
+  1[053] - invoke static is_int tests/type_propagation/typecheck_test.toit // [{Null_}] -> {False_}
+  4[053] - invoke static id tests/type_propagation/typecheck_test.toit // [{False_}] -> {False_}
   7[041] - pop 1
   8[026] - load smi 7
- 10[053] - invoke static is_int tests/type_propagation/typecheck_test.toit // {True_}
- 13[053] - invoke static id tests/type_propagation/typecheck_test.toit // {True_}
+ 10[053] - invoke static is_int tests/type_propagation/typecheck_test.toit // [{SmallInteger_}] -> {True_}
+ 13[053] - invoke static id tests/type_propagation/typecheck_test.toit // [{True_}] -> {True_}
  16[041] - pop 1
  17[020] - load literal 7.9000000000000003553
- 19[053] - invoke static is_int tests/type_propagation/typecheck_test.toit // {False_}
- 22[053] - invoke static id tests/type_propagation/typecheck_test.toit // {False_}
+ 19[053] - invoke static is_int tests/type_propagation/typecheck_test.toit // [{float}] -> {False_}
+ 22[053] - invoke static id tests/type_propagation/typecheck_test.toit // [{False_}] -> {False_}
  25[041] - pop 1
  26[020] - load literal kurt
- 28[053] - invoke static is_int tests/type_propagation/typecheck_test.toit // {False_}
- 31[053] - invoke static id tests/type_propagation/typecheck_test.toit // {False_}
+ 28[053] - invoke static is_int tests/type_propagation/typecheck_test.toit // [{String_}] -> {False_}
+ 31[053] - invoke static id tests/type_propagation/typecheck_test.toit // [{False_}] -> {False_}
  34[089] - return null S1 0
 
 test_any tests/type_propagation/typecheck_test.toit
   0[020] - load literal true
-  2[053] - invoke static id tests/type_propagation/typecheck_test.toit // {True_}
+  2[053] - invoke static id tests/type_propagation/typecheck_test.toit // [{True_}] -> {True_}
   5[041] - pop 1
   6[020] - load literal true
-  8[053] - invoke static id tests/type_propagation/typecheck_test.toit // {True_}
+  8[053] - invoke static id tests/type_propagation/typecheck_test.toit // [{True_}] -> {True_}
  11[041] - pop 1
  12[026] - load smi 7
- 14[053] - invoke static id tests/type_propagation/typecheck_test.toit // {SmallInteger_}
+ 14[053] - invoke static id tests/type_propagation/typecheck_test.toit // [{SmallInteger_}] -> {SmallInteger_}
  17[041] - pop 1
  18[020] - load literal hest
- 20[053] - invoke static id tests/type_propagation/typecheck_test.toit // {String_}
+ 20[053] - invoke static id tests/type_propagation/typecheck_test.toit // [{String_}] -> {String_}
  23[089] - return null S1 0
 
 test_throws tests/type_propagation/typecheck_test.toit
@@ -43,13 +43,13 @@ test_throws tests/type_propagation/typecheck_test.toit
   5[038] - load block 0
   7[022] - load null
   8[022] - load null
-  9[053] - invoke static catch <sdk>/core/exceptions.toit // {*}
+  9[053] - invoke static catch <sdk>/core/exceptions.toit // [[block], {Null_}, {Null_}] -> {*}
  12[040] - pop 2
  14[029] - load [block] in test_throws tests/type_propagation/typecheck_test.toit
  19[038] - load block 0
  21[022] - load null
  22[022] - load null
- 23[053] - invoke static catch <sdk>/core/exceptions.toit // {*}
+ 23[053] - invoke static catch <sdk>/core/exceptions.toit // [[block], {Null_}, {Null_}] -> {*}
  26[089] - return null S2 0
 
 [block] in test_throws tests/type_propagation/typecheck_test.toit
@@ -61,7 +61,7 @@ test_throws tests/type_propagation/typecheck_test.toit
 [block] in test_throws tests/type_propagation/typecheck_test.toit
  - argument 0: [block]
   0[026] - load smi 7
-  2[053] - invoke static bar tests/type_propagation/typecheck_test.toit // {}
+  2[053] - invoke static bar tests/type_propagation/typecheck_test.toit // [{SmallInteger_}] -> {}
   5[088] - return S1 1
 
 foo tests/type_propagation/typecheck_test.toit
diff --git a/tools/dump_types.toit b/tools/dump_types.toit
index ae0932c3b..bb9fdf922 100644
--- a/tools/dump_types.toit
+++ b/tools/dump_types.toit
@@ -63,14 +63,18 @@ show_types types/List snapshot_content/ByteArray -> none
   bundle := SnapshotBundle snapshot_content
   program := bundle.decode
   methods := {}
-  type_strings := {:}
+  input_strings := {:}
+  output_strings := {:}
   method_args := {:}
   types.do: | entry/Map |
     position := entry["position"]
     method/ToitMethod := ?
-    if entry.contains "type":
+    if entry.contains "output":
       method = program.method_from_absolute_bci position
-      type_strings[position] = type_string program entry["type"]
+      output_strings[position] = type_string program entry["output"]
+      if entry.contains "input":
+        input_strings[position] = entry["input"].map: | x |
+          type_string program x
     else:
       method = program.method_from_absolute_bci (position + ToitMethod.HEADER_SIZE)
       method_args[position] = entry["arguments"].map: | x |
@@ -101,7 +105,9 @@ show_types types/List snapshot_content/ByteArray -> none
     else: print ""
     args := method_args.get method.id
     method.output program args --show_positions=show_positions: | position/int |
-      type_strings.get position
+      input_part := input_strings.get position
+      output_part := output_strings.get position
+      input_part ? "$input_part -> $output_part" : output_part
 
 type_string program/Program type/any -> string:
   if type == "[]": return "[block]"