diff --git a/src/cli/lib.rs b/src/cli/lib.rs
index 182c6e7e..ef32cdf2 100644
--- a/src/cli/lib.rs
+++ b/src/cli/lib.rs
@@ -9,7 +9,7 @@ use hakana_reflection_info::Interner;
 use indexmap::IndexMap;
 use rand::Rng;
 use rustc_hash::FxHashSet;
-use std::collections::BTreeMap;
+use std::collections::{BTreeMap, BTreeSet};
 use std::env;
 use std::fs::{self, File};
 use std::io::Write;
@@ -1056,15 +1056,17 @@ fn do_codegen(
                     errors.push(format!("File {} doesn’t exist", name));
                     continue;
                 }
-            } else if check_codegen || !overwrite_codegen {
+            } else {
                 let existing_contents = fs::read_to_string(path).unwrap();
                 if existing_contents.trim() != info.trim() {
-                    errors.push(format!("File {} differs from codegen", name,));
+                    if check_codegen || !overwrite_codegen {
+                        errors.push(format!("File {} differs from codegen", name));
+                        continue;
+                    }
                 } else {
                     verified_count += 1;
+                    continue;
                 }
-
-                continue;
             }
 
             if let Some(dir) = path.parent() {
@@ -1072,6 +1074,7 @@ fn do_codegen(
             }
             let mut output_path = fs::File::create(path).unwrap();
             write!(output_path, "{}", &info).unwrap();
+            println!("Saved {}", name);
             updated_count += 1;
         }
 
diff --git a/src/code_info/t_atomic.rs b/src/code_info/t_atomic.rs
index e6e45b78..2e5ba0ff 100644
--- a/src/code_info/t_atomic.rs
+++ b/src/code_info/t_atomic.rs
@@ -161,24 +161,33 @@ pub enum TAtomic {
 
 impl TAtomic {
     pub fn get_id(&self, interner: Option<&Interner>) -> String {
-        self.get_id_with_refs(interner, &mut vec![])
+        self.get_id_with_refs(interner, &mut vec![], None)
     }
 
-    pub fn get_id_with_refs(&self, interner: Option<&Interner>, refs: &mut Vec<StrId>) -> String {
+    pub fn get_id_with_refs(
+        &self,
+        interner: Option<&Interner>,
+        refs: &mut Vec<StrId>,
+        indent: Option<usize>,
+    ) -> String {
         match self {
             TAtomic::TArraykey { .. } => "arraykey".to_string(),
             TAtomic::TBool { .. } => "bool".to_string(),
             TAtomic::TClassname { as_type, .. } => {
                 let mut str = String::new();
                 str += "classname<";
-                str += as_type.get_id_with_refs(interner, &mut vec![]).as_str();
+                str += as_type
+                    .get_id_with_refs(interner, &mut vec![], indent)
+                    .as_str();
                 str += ">";
                 str
             }
             TAtomic::TTypename { as_type, .. } => {
                 let mut str = String::new();
                 str += "typename<";
-                str += as_type.get_id_with_refs(interner, &mut vec![]).as_str();
+                str += as_type
+                    .get_id_with_refs(interner, &mut vec![], indent)
+                    .as_str();
                 str += ">";
                 str
             }
@@ -215,6 +224,11 @@ impl TAtomic {
                 if let Some(known_items) = known_items {
                     str += "shape(";
 
+                    if let Some(indent) = indent {
+                        str += "\n";
+                        str += &("\t".repeat(indent + 1));
+                    }
+
                     str += known_items
                         .iter()
                         .map(|(property, (u, property_type))| {
@@ -222,29 +236,52 @@ impl TAtomic {
                                 "{}{} => {}",
                                 if *u { "?" } else { "" },
                                 property.to_string(interner),
-                                property_type.get_id_with_refs(interner, refs)
+                                property_type.get_id_with_refs(
+                                    interner,
+                                    refs,
+                                    if let Some(indent) = indent {
+                                        Some(indent + 1)
+                                    } else {
+                                        None
+                                    }
+                                )
                             )
                         })
-                        .join(", ")
+                        .join(&if let Some(indent) = indent {
+                            format!("\n{}", "\t".repeat(indent + 1))
+                        } else {
+                            ", ".to_string()
+                        })
                         .as_str();
 
                     if let Some(params) = params {
-                        str += ", ...dict<";
-                        str += params.0.get_id_with_refs(interner, refs).as_str();
-                        str += ",";
-                        str += params.1.get_id_with_refs(interner, refs).as_str();
+                        if let Some(indent) = indent {
+                            str += &format!("\n{}", "\t".repeat(indent + 1));
+                        } else {
+                            str += ", "
+                        }
+
+                        str += "...dict<";
+                        str += params.0.get_id_with_refs(interner, refs, indent).as_str();
+                        str += ", ";
+                        str += params.1.get_id_with_refs(interner, refs, indent).as_str();
                         str += ">";
                     }
 
+                    if let Some(indent) = indent {
+                        str += "\n";
+                        str += &("\t".repeat(indent));
+                    }
+
                     str += ")";
                     return str;
                 }
 
                 if let Some(params) = params {
                     str += "dict<";
-                    str += params.0.get_id_with_refs(interner, refs).as_str();
-                    str += ",";
-                    str += params.1.get_id_with_refs(interner, refs).as_str();
+                    str += params.0.get_id_with_refs(interner, refs, indent).as_str();
+                    str += ", ";
+                    str += params.1.get_id_with_refs(interner, refs, indent).as_str();
                     str += ">";
                     str
                 } else {
@@ -275,7 +312,7 @@ impl TAtomic {
                         format!(
                             "{}{}",
                             if let Some(param_type) = &param.signature_type {
-                                param_type.get_id_with_refs(interner, refs)
+                                param_type.get_id_with_refs(interner, refs, indent)
                             } else {
                                 "mixed".to_string()
                             },
@@ -287,7 +324,9 @@ impl TAtomic {
 
                 str += "): ";
                 if let Some(return_type) = return_type {
-                    str += return_type.get_id_with_refs(interner, refs).as_str();
+                    str += return_type
+                        .get_id_with_refs(interner, refs, indent)
+                        .as_str();
                 } else {
                     str += "mixed";
                 }
@@ -311,7 +350,7 @@ impl TAtomic {
             TAtomic::TKeyset { type_param, .. } => {
                 let mut str = String::new();
                 str += "keyset<";
-                str += type_param.get_id_with_refs(interner, refs).as_str();
+                str += type_param.get_id_with_refs(interner, refs, indent).as_str();
                 str += ">";
                 str
             }
@@ -403,7 +442,7 @@ impl TAtomic {
                             "&".to_string()
                                 + extra_types
                                     .iter()
-                                    .map(|atomic| atomic.get_id_with_refs(interner, refs))
+                                    .map(|atomic| atomic.get_id_with_refs(interner, refs, indent))
                                     .join("&")
                                     .as_str()
                         } else {
@@ -423,7 +462,7 @@ impl TAtomic {
                         str += "<";
                         str += type_params
                             .iter()
-                            .map(|tunion| tunion.get_id_with_refs(interner, refs))
+                            .map(|tunion| tunion.get_id_with_refs(interner, refs, indent))
                             .join(", ")
                             .as_str();
                         str += ">";
@@ -457,7 +496,7 @@ impl TAtomic {
                         str += "<";
                         str += type_params
                             .iter()
-                            .map(|tunion| tunion.get_id_with_refs(interner, refs))
+                            .map(|tunion| tunion.get_id_with_refs(interner, refs, indent))
                             .join(", ")
                             .as_str();
                         str += ">)";
@@ -558,13 +597,13 @@ impl TAtomic {
                     str += "tuple(";
                     str += known_items
                         .iter()
-                        .map(|(_, (_, tunion))| tunion.get_id_with_refs(interner, refs))
+                        .map(|(_, (_, tunion))| tunion.get_id_with_refs(interner, refs, indent))
                         .join(", ")
                         .as_str();
 
                     if !type_param.is_nothing() {
                         str += ", ...vec<";
-                        str += type_param.get_id_with_refs(interner, refs).as_str();
+                        str += type_param.get_id_with_refs(interner, refs, indent).as_str();
                         str += ">";
                     }
 
@@ -573,7 +612,7 @@ impl TAtomic {
                 }
                 let mut str = String::new();
                 str += if *non_empty { "non-empty-vec<" } else { "vec<" };
-                str += type_param.get_id_with_refs(interner, refs).as_str();
+                str += type_param.get_id_with_refs(interner, refs, indent).as_str();
                 str += ">";
                 str
             }
@@ -597,7 +636,7 @@ impl TAtomic {
             } => {
                 format!(
                     "{}::{}",
-                    class_type.get_id_with_refs(interner, refs),
+                    class_type.get_id_with_refs(interner, refs, indent),
                     if let Some(interner) = interner {
                         interner.lookup(member_name).to_string()
                     } else {
@@ -676,7 +715,7 @@ impl TAtomic {
             | TAtomic::TBool { .. }
             | TAtomic::TEnumClassLabel { .. }
             | TAtomic::TMixedWithFlags(..)
-            | TAtomic::TTypeVariable { .. } => self.get_id_with_refs(None, &mut vec![]),
+            | TAtomic::TTypeVariable { .. } => self.get_id_with_refs(None, &mut vec![], None),
 
             TAtomic::TStringWithFlags(..) => "string".to_string(),
 
diff --git a/src/code_info/t_union.rs b/src/code_info/t_union.rs
index 86f16098..e1810d4f 100644
--- a/src/code_info/t_union.rs
+++ b/src/code_info/t_union.rs
@@ -488,15 +488,35 @@ impl TUnion {
     }
 
     pub fn get_id(&self, interner: Option<&Interner>) -> String {
-        self.get_id_with_refs(interner, &mut vec![])
-    }
-
-    pub fn get_id_with_refs(&self, interner: Option<&Interner>, refs: &mut Vec<StrId>) -> String {
-        let mut tatomic_strings = self
-            .types
-            .iter()
-            .map(|atomic| atomic.get_id_with_refs(interner, refs));
-        tatomic_strings.join("|")
+        self.get_id_with_refs(interner, &mut vec![], None)
+    }
+
+    pub fn get_id_with_refs(
+        &self,
+        interner: Option<&Interner>,
+        refs: &mut Vec<StrId>,
+        indent: Option<usize>,
+    ) -> String {
+        if self.types.len() == 2 {
+            match (&self.types[0], &self.types[1]) {
+                (TAtomic::TNull, a) | (a, TAtomic::TNull) => {
+                    format!("?{}", a.get_id_with_refs(interner, refs, indent))
+                }
+                (a, b) => {
+                    format!(
+                        "{}|{}",
+                        a.get_id_with_refs(interner, refs, indent),
+                        b.get_id_with_refs(interner, refs, indent)
+                    )
+                }
+            }
+        } else {
+            let mut tatomic_strings = self
+                .types
+                .iter()
+                .map(|atomic| atomic.get_id_with_refs(interner, refs, indent));
+            tatomic_strings.join("|")
+        }
     }
 
     #[inline]
diff --git a/tests/diff/classConstTypeChanged/output.txt b/tests/diff/classConstTypeChanged/output.txt
index c8a06373..9b4a7d50 100644
--- a/tests/diff/classConstTypeChanged/output.txt
+++ b/tests/diff/classConstTypeChanged/output.txt
@@ -1 +1 @@
-ERROR: InvalidArgument - input.hack:13:14 - Argument 1 of echo expects scalar|null, different type Exception provided
\ No newline at end of file
+ERROR: InvalidArgument - input.hack:13:14 - Argument 1 of echo expects ?scalar, different type Exception provided
\ No newline at end of file
diff --git a/tests/diff/commentOutClassInOtherFile/output.txt b/tests/diff/commentOutClassInOtherFile/output.txt
index 66040115..bc7ecf4a 100644
--- a/tests/diff/commentOutClassInOtherFile/output.txt
+++ b/tests/diff/commentOutClassInOtherFile/output.txt
@@ -1,7 +1,7 @@
 ERROR: NonExistentClass - input.hack:8:11 - Cannot call new on undefined class A
 ERROR: NonExistentType - input.hack:12:10 - Unknown class A
-ERROR: MixedAnyArgument - input.hack:12:10 - Argument 1 of echo expects scalar|null, any provided
+ERROR: MixedAnyArgument - input.hack:12:10 - Argument 1 of echo expects ?scalar, any provided
 ERROR: NonExistentType - input.hack:17:14 - Unknown class A
-ERROR: MixedAnyArgument - input.hack:17:14 - Argument 1 of echo expects scalar|null, any provided
+ERROR: MixedAnyArgument - input.hack:17:14 - Argument 1 of echo expects ?scalar, any provided
 ERROR: NonExistentClass - input.hack:21:15 - Cannot call new on undefined class A
 ERROR: InvalidReturnStatement - input.hack:26:16 - The type string(a) does not match the declared return type int for B::bat
\ No newline at end of file
diff --git a/tests/inference/ArrayAccess/mixedArrayAccessDictWrapped/output.txt b/tests/inference/ArrayAccess/mixedArrayAccessDictWrapped/output.txt
index b277897e..8682acdf 100644
--- a/tests/inference/ArrayAccess/mixedArrayAccessDictWrapped/output.txt
+++ b/tests/inference/ArrayAccess/mixedArrayAccessDictWrapped/output.txt
@@ -1,2 +1,2 @@
-ERROR: PossiblyUndefinedStringArrayOffset - input.hack:6:10 - Fetch on dict<arraykey,any> using possibly-undefined key 'foo'
-ERROR: MixedAnyArgument - input.hack:6:10 - Argument 1 of echo expects scalar|null, any provided
\ No newline at end of file
+ERROR: PossiblyUndefinedStringArrayOffset - input.hack:6:10 - Fetch on dict<arraykey, any> using possibly-undefined key 'foo'
+ERROR: MixedAnyArgument - input.hack:6:10 - Argument 1 of echo expects ?scalar, any provided
\ No newline at end of file
diff --git a/tests/inference/ArrayAssignment/nestedKeysetAddition/output.txt b/tests/inference/ArrayAssignment/nestedKeysetAddition/output.txt
index ef78f0f0..bfe5303f 100644
--- a/tests/inference/ArrayAssignment/nestedKeysetAddition/output.txt
+++ b/tests/inference/ArrayAssignment/nestedKeysetAddition/output.txt
@@ -1 +1 @@
-InvalidReturnStatement - input.hack:9:12 - The type dict<string,keyset<int>> does not match the declared return type dict<string,keyset<string>> for foo
\ No newline at end of file
+InvalidReturnStatement - input.hack:9:12 - The type dict<string, keyset<int>> does not match the declared return type dict<string, keyset<string>> for foo
\ No newline at end of file
diff --git a/tests/inference/ArrayFunctionCall/arrayContains/checksKeyIfArrayTypeMatch/output.txt b/tests/inference/ArrayFunctionCall/arrayContains/checksKeyIfArrayTypeMatch/output.txt
index 0f293503..34219e8a 100644
--- a/tests/inference/ArrayFunctionCall/arrayContains/checksKeyIfArrayTypeMatch/output.txt
+++ b/tests/inference/ArrayFunctionCall/arrayContains/checksKeyIfArrayTypeMatch/output.txt
@@ -1,4 +1,4 @@
 ERROR: ImpossibleKeyCheck - input.hack:7:9 - Type vec<string> never has key 's'
 ERROR: ImpossibleKeyCheck - input.hack:11:9 - Type vec<string> never has key 't'
-ERROR: ImpossibleKeyCheck - input.hack:24:9 - Type dict<string,string> never has key 1
-ERROR: ImpossibleKeyCheck - input.hack:28:9 - Type dict<string,string> never has key 2
\ No newline at end of file
+ERROR: ImpossibleKeyCheck - input.hack:24:9 - Type dict<string, string> never has key 1
+ERROR: ImpossibleKeyCheck - input.hack:28:9 - Type dict<string, string> never has key 2
\ No newline at end of file
diff --git a/tests/inference/DictVecKeyset/dictFromKeys/output.txt b/tests/inference/DictVecKeyset/dictFromKeys/output.txt
index c80c613f..dc1eceef 100644
--- a/tests/inference/DictVecKeyset/dictFromKeys/output.txt
+++ b/tests/inference/DictVecKeyset/dictFromKeys/output.txt
@@ -1,3 +1,3 @@
-ERROR: LessSpecificNestedAnyReturnStatement - input.hack:2:12 - The type dict<arraykey,string> is more general than the declared return type dict<string,string> for foo
+ERROR: LessSpecificNestedAnyReturnStatement - input.hack:2:12 - The type dict<arraykey, string> is more general than the declared return type dict<string, string> for foo
 ERROR: MixedArgument - input.hack:3:9 - Argument 1 of HH\Lib\Dict\from_keys expects HH\Traversable<arraykey>, mixed provided
 ERROR: LessSpecificNestedAnyArgumentType - input.hack:4:28 - Argument 1 of takesString expects string, parent type arraykey provided
\ No newline at end of file
diff --git a/tests/inference/DictVecKeyset/lessSpecificTypeFromDictMixed/output.txt b/tests/inference/DictVecKeyset/lessSpecificTypeFromDictMixed/output.txt
index 1b67afdf..8e77e3ea 100644
--- a/tests/inference/DictVecKeyset/lessSpecificTypeFromDictMixed/output.txt
+++ b/tests/inference/DictVecKeyset/lessSpecificTypeFromDictMixed/output.txt
@@ -1,4 +1,4 @@
-ERROR: LessSpecificNestedAnyArgumentType - input.hack:6:14 - Argument 1 of foo1 expects shape('id' => string, 'name' => string), parent type dict<arraykey,any> provided
-ERROR: LessSpecificNestedAnyArgumentType - input.hack:7:14 - Argument 1 of foo2 expects shape('id' => string, 'name' => string, ...dict<arraykey,any>), parent type dict<arraykey,any> provided
-ERROR: LessSpecificNestedArgumentType - input.hack:12:10 - Argument 1 of foo1 expects shape('id' => string, 'name' => string), parent type dict<string,mixed> provided
-ERROR: LessSpecificNestedArgumentType - input.hack:13:10 - Argument 1 of foo2 expects shape('id' => string, 'name' => string, ...dict<arraykey,any>), parent type dict<string,mixed> provided
\ No newline at end of file
+ERROR: LessSpecificNestedAnyArgumentType - input.hack:6:14 - Argument 1 of foo1 expects shape('id' => string, 'name' => string), parent type dict<arraykey, any> provided
+ERROR: LessSpecificNestedAnyArgumentType - input.hack:7:14 - Argument 1 of foo2 expects shape('id' => string, 'name' => string, ...dict<arraykey, any>), parent type dict<arraykey, any> provided
+ERROR: LessSpecificNestedArgumentType - input.hack:12:10 - Argument 1 of foo1 expects shape('id' => string, 'name' => string), parent type dict<string, mixed> provided
+ERROR: LessSpecificNestedArgumentType - input.hack:13:10 - Argument 1 of foo2 expects shape('id' => string, 'name' => string, ...dict<arraykey, any>), parent type dict<string, mixed> provided
\ No newline at end of file
diff --git a/tests/inference/DictVecKeyset/vecAnyIntoTypedVec/output.txt b/tests/inference/DictVecKeyset/vecAnyIntoTypedVec/output.txt
index 74302686..14145c8d 100644
--- a/tests/inference/DictVecKeyset/vecAnyIntoTypedVec/output.txt
+++ b/tests/inference/DictVecKeyset/vecAnyIntoTypedVec/output.txt
@@ -1,2 +1,2 @@
 ERROR: MixedAnyArgument - input.hack:4:29 - Argument 1 of HH\vec expects HH\Traversable<any>, any provided
-ERROR: LessSpecificNestedAnyArgumentType - input.hack:6:9 - Argument 1 of foo expects shape('a' => null|vec<shape('b' => string)>), parent type shape('a' => vec<any>|null) provided
\ No newline at end of file
+ERROR: LessSpecificNestedAnyArgumentType - input.hack:6:9 - Argument 1 of foo expects shape('a' => ?vec<shape('b' => string)>), parent type shape('a' => ?vec<any>) provided
\ No newline at end of file
diff --git a/tests/inference/Interface/interfaceRequireExtendsClassNegation/output.txt b/tests/inference/Interface/interfaceRequireExtendsClassNegation/output.txt
index 24733963..15ba01c4 100644
--- a/tests/inference/Interface/interfaceRequireExtendsClassNegation/output.txt
+++ b/tests/inference/Interface/interfaceRequireExtendsClassNegation/output.txt
@@ -1 +1 @@
-ERROR: InvalidArgument - input.hack:21:10 - Argument 1 of echo expects scalar|null, different type Node provided
\ No newline at end of file
+ERROR: InvalidArgument - input.hack:21:10 - Argument 1 of echo expects ?scalar, different type Node provided
\ No newline at end of file
diff --git a/tests/inference/TypeAlias/classConstTypeAlias/output.txt b/tests/inference/TypeAlias/classConstTypeAlias/output.txt
index aefd98c6..7fba5c40 100644
--- a/tests/inference/TypeAlias/classConstTypeAlias/output.txt
+++ b/tests/inference/TypeAlias/classConstTypeAlias/output.txt
@@ -1 +1 @@
-ERROR: InvalidArgument - input.hack:11:14 - Argument 1 of echo expects scalar|null, different type Exception provided
\ No newline at end of file
+ERROR: InvalidArgument - input.hack:11:14 - Argument 1 of echo expects ?scalar, different type Exception provided
\ No newline at end of file
diff --git a/tests/inference/TypeAlias/classConstTypeAliasViaTrait/output.txt b/tests/inference/TypeAlias/classConstTypeAliasViaTrait/output.txt
index cc3c2864..9562cf77 100644
--- a/tests/inference/TypeAlias/classConstTypeAliasViaTrait/output.txt
+++ b/tests/inference/TypeAlias/classConstTypeAliasViaTrait/output.txt
@@ -1 +1 @@
-ERROR: InvalidArgument - input.hack:23:14 - Argument 1 of echo expects scalar|null, different type Exception provided
\ No newline at end of file
+ERROR: InvalidArgument - input.hack:23:14 - Argument 1 of echo expects ?scalar, different type Exception provided
\ No newline at end of file
diff --git a/tests/inference/TypeReconciliation/AsExpression/nestedAnyArrayAccess/output.txt b/tests/inference/TypeReconciliation/AsExpression/nestedAnyArrayAccess/output.txt
index 41907c9d..be849fbf 100644
--- a/tests/inference/TypeReconciliation/AsExpression/nestedAnyArrayAccess/output.txt
+++ b/tests/inference/TypeReconciliation/AsExpression/nestedAnyArrayAccess/output.txt
@@ -1,4 +1,4 @@
 ERROR: MixedAnyArrayAccess - input.hack:3:10 - Unsafe array access on value with type any
 ERROR: MixedAnyArrayAccess - input.hack:4:10 - Unsafe array access on value with type nonnull-from-any
-ERROR: MixedAnyArgument - input.hack:4:10 - Argument 1 of echo expects scalar|null, any provided
+ERROR: MixedAnyArgument - input.hack:4:10 - Argument 1 of echo expects ?scalar, any provided
 ERROR: MixedAnyReturnStatement - input.hack:5:12 - Could not infer a proper return type — saw nonnull-from-any
\ No newline at end of file
diff --git a/tests/nopanic/noclass/output.txt b/tests/nopanic/noclass/output.txt
index b3e72fbe..2dfdb72f 100644
--- a/tests/nopanic/noclass/output.txt
+++ b/tests/nopanic/noclass/output.txt
@@ -1,15 +1,15 @@
 ERROR: NonExistentClass - input.hack:2:12 - Cannot call new on undefined class Foo
 ERROR: MixedAnyReturnStatement - input.hack:2:12 - Could not infer a proper return type — saw any
 ERROR: NonExistentClasslike - input.hack:6:10 - Unknown classlike Foo
-ERROR: MixedAnyArgument - input.hack:6:10 - Argument 1 of echo expects scalar|null, any provided
+ERROR: MixedAnyArgument - input.hack:6:10 - Argument 1 of echo expects ?scalar, any provided
 ERROR: NonExistentClasslike - input.hack:9:12 - Class, enum or interface Foo cannot be found
 ERROR: NonExistentClasslike - input.hack:13:10 - Unknown classlike Foo
-ERROR: MixedAnyArgument - input.hack:13:10 - Argument 1 of echo expects scalar|null, any provided
+ERROR: MixedAnyArgument - input.hack:13:10 - Argument 1 of echo expects ?scalar, any provided
 ERROR: NonExistentClasslike - input.hack:23:5 - Unknown classlike Foo
 ERROR: NonExistentClass - input.hack:28:10 - Cannot access property on undefined class Foo
-ERROR: MixedAnyArgument - input.hack:28:10 - Argument 1 of echo expects scalar|null, any provided
+ERROR: MixedAnyArgument - input.hack:28:10 - Argument 1 of echo expects ?scalar, any provided
 ERROR: NonExistentClass - input.hack:33:10 - Cannot access property on undefined class Foo
-ERROR: InvalidArgument - input.hack:33:10 - Argument 1 of echo expects scalar|null, different type unknown-ref(Foo) provided
+ERROR: InvalidArgument - input.hack:33:10 - Argument 1 of echo expects ?scalar, different type unknown-ref(Foo) provided
 ERROR: NonExistentClass - input.hack:37:10 - Cannot access property on undefined class Foo
-ERROR: MixedAnyArgument - input.hack:37:10 - Argument 1 of echo expects scalar|null, any provided
+ERROR: MixedAnyArgument - input.hack:37:10 - Argument 1 of echo expects ?scalar, any provided
 ERROR: NonExistentClass - input.hack:42:9 - Undefined class Foo
diff --git a/tests/nopanic/noclasslikemember/output.txt b/tests/nopanic/noclasslikemember/output.txt
index ca833f35..f3e31d18 100644
--- a/tests/nopanic/noclasslikemember/output.txt
+++ b/tests/nopanic/noclasslikemember/output.txt
@@ -1,13 +1,13 @@
 ERROR: NonExistentClassConstant - input.hack:8:10 - Unknown class constant Foo::B1
-ERROR: MixedAnyArgument - input.hack:8:10 - Argument 1 of echo expects scalar|null, any provided
+ERROR: MixedAnyArgument - input.hack:8:10 - Argument 1 of echo expects ?scalar, any provided
 ERROR: NonExistentClassConstant - input.hack:16:5 - Unknown class constant Foo::B3
 ERROR: NonExistentClassConstant - input.hack:20:10 - Unknown class constant Foo::B4
-ERROR: MixedAnyArgument - input.hack:20:10 - Argument 1 of echo expects scalar|null, any provided
+ERROR: MixedAnyArgument - input.hack:20:10 - Argument 1 of echo expects ?scalar, any provided
 ERROR: NonExistentMethod - input.hack:24:5 - Method Foo::b5 does not exist
 ERROR: NonExistentMethod - input.hack:28:5 - Method Foo::b6 does not exist
 ERROR: NonExistentProperty - input.hack:32:10 - Cannot access undefined property Foo::$b7
-ERROR: MixedAnyArgument - input.hack:32:10 - Argument 1 of echo expects scalar|null, any provided
+ERROR: MixedAnyArgument - input.hack:32:10 - Argument 1 of echo expects ?scalar, any provided
 ERROR: NonExistentProperty - input.hack:36:10 - Cannot access undefined property Foo::$b8
-ERROR: InvalidArgument - input.hack:36:10 - Argument 1 of echo expects scalar|null, different type Foo provided
+ERROR: InvalidArgument - input.hack:36:10 - Argument 1 of echo expects ?scalar, different type Foo provided
 ERROR: NonExistentProperty - input.hack:40:10 - Property Foo::$b9 is undefined
 ERROR: NonExistentProperty - input.hack:44:9 - Undefined property Foo::$b10
diff --git a/tests/nopanic/nofunction/output.txt b/tests/nopanic/nofunction/output.txt
index ccfbb858..41277030 100644
--- a/tests/nopanic/nofunction/output.txt
+++ b/tests/nopanic/nofunction/output.txt
@@ -1,4 +1,4 @@
 ERROR: NonExistentFunction - input.hack:2:5 - Function f1 is not defined
 ERROR: NonExistentFunction - input.hack:6:10 - Unknown function f2
-ERROR: MixedAnyArgument - input.hack:6:10 - Argument 1 of echo expects scalar|null, any provided
+ERROR: MixedAnyArgument - input.hack:6:10 - Argument 1 of echo expects ?scalar, any provided
 ERROR: NonExistentFunction - input.hack:10:5 - Function f3 is not defined
\ No newline at end of file