constants

vajexal · Jun 11, 2024 · 16a9985 · 16a9985
1 parent 5ff6705
commit 16a9985
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Showing 9 changed files with 103 additions and 8 deletions.
diff --git a/readme.md b/readme.md
@@ -81,7 +81,8 @@ fn types() void {
     []Foo arr = [new Foo(), new Foo()]
 }
 
-auto PI = 3.14 // globals
+auto qux = 123 // globals
+const auto PI = 3.14 // consts
 
 fn flow() void {
     // will print "then"

diff --git a/src/lexer.l b/src/lexer.l
@@ -32,10 +32,10 @@ yy::parser::symbol_type yylex(Driver &driver) {
       "string" { return yy::parser::make_STRING_TYPE(driver.location); }
       "void" { return yy::parser::make_VOID_TYPE(driver.location); }
       "auto" { return yy::parser::make_AUTO_TYPE(driver.location); }
+      "const" { return yy::parser::make_CONST(driver.location); }
       "false" { return yy::parser::make_BOOL(false, driver.location); }
       "true" { return yy::parser::make_BOOL(true, driver.location); }
       "fn" { return yy::parser::make_FN(driver.location); }
-      "var" { return yy::parser::make_VAR(driver.location); }
       "case" { return yy::parser::make_CASE(driver.location); }
       "default" { return yy::parser::make_DEFAULT(driver.location); }
       "if" { return yy::parser::make_IF(driver.location); }

diff --git a/src/parser.y b/src/parser.y
@@ -40,8 +40,8 @@
 %token STRING_TYPE "string"
 %token VOID_TYPE "void"
 %token AUTO_TYPE "auto"
+%token CONST "const"
 %token FN "fn"
-%token VAR "var"
 %token <std::string> IDENTIFIER
 %token CASE "case"
 %token DEFAULT "default"
@@ -95,6 +95,7 @@
 %nterm <Type> array_type
 %nterm <Type> return_type
 %nterm <DeclNode *> var_decl
+%nterm <DeclNode *> id_decl
 %nterm <VarNode *> identifier
 %nterm <std::string> static_identifier
 %nterm <ScalarNode *> scalar
@@ -243,6 +244,11 @@ type { $$ = std::move($1); }
 ;
 
 var_decl:
+CONST id_decl { $2->type.makeConst(); $$ = $2; }
+| id_decl { $$ = $1; }
+;
+
+id_decl:
 type IDENTIFIER '=' expr { $$ = new DeclNode(std::move($1), std::move($2), $4); }
 | AUTO_TYPE IDENTIFIER '=' expr { $$ = new DeclNode(Type::autoTy(), std::move($2), $4); }
 | type IDENTIFIER { $$ = new DeclNode(std::move($1), std::move($2)); }
@@ -380,7 +386,7 @@ COMMENT { $$ = new CommentNode(std::move($1)); }
 ;
 
 prop_decl:
-access_modifier optional_static var_decl { $$ = new PropDeclNode($3, $1, $2); }
+access_modifier optional_static id_decl { $$ = new PropDeclNode($3, $1, $2); }
 ;
 
 method_def:

diff --git a/src/pipes/type_inferrer.cpp b/src/pipes/type_inferrer.cpp
@@ -280,9 +280,14 @@ namespace X::Pipes {
     }
 
     Type TypeInferrer::infer(AssignNode *node) {
-        auto exprType = node->expr->infer(*this);
         auto varType = getVarType(node->name);
 
+        if (varType.isConst()) {
+            throw ModifyConstException();
+        }
+
+        auto exprType = node->expr->infer(*this);
+
         if (!canCastTo(exprType, varType)) {
             throw InvalidTypeException();
         }
@@ -609,6 +614,10 @@ namespace X::Pipes {
             throw InvalidTypeException();
         }
 
+        if (arrType.isConst()) {
+            throw ModifyConstException();
+        }
+
         auto idxType = node->idx->infer(*this);
         if (!idxType.is(Type::TypeID::INT)) {
             throw InvalidTypeException();
@@ -628,6 +637,10 @@ namespace X::Pipes {
             throw InvalidTypeException();
         }
 
+        if (arrType.isConst()) {
+            throw ModifyConstException();
+        }
+
         auto exprType = node->expr->infer(*this);
         if (!canCastTo(exprType, *arrType.getSubtype())) {
             throw InvalidTypeException();
@@ -679,6 +692,10 @@ namespace X::Pipes {
 
             checkLvalueTypeIsValid(exprType);
 
+            if (type.isConst()) {
+                exprType.makeConst();
+            }
+
             node->type = exprType;
 
             return;

diff --git a/src/pipes/type_inferrer.h b/src/pipes/type_inferrer.h
@@ -107,4 +107,9 @@ namespace X::Pipes {
     public:
         InvalidTypeException() : TypeInferrerException("invalid type") {}
     };
+
+    class ModifyConstException : public TypeInferrerException {
+    public:
+        ModifyConstException() : TypeInferrerException("can't modify const") {}
+    };
 }
diff --git a/src/type.cpp b/src/type.cpp
@@ -1,7 +1,7 @@
 #include "type.h"
 
 namespace X {
-    Type::Type(const Type &type) : id(type.id) {
+    Type::Type(const Type &type) : id(type.id), constant(type.constant) {
         if (type.className) {
             className = type.className.value();
         }
@@ -11,14 +11,16 @@ namespace X {
         }
     }
 
-    Type::Type(Type &&type) : id(type.id), className(std::move(type.className)), subtype(type.subtype) {
+    Type::Type(Type &&type) : id(type.id), className(std::move(type.className)), subtype(type.subtype), constant(type.constant) {
         type.id = TypeID::VOID;
         type.className = std::nullopt;
         type.subtype = nullptr;
+        type.constant = false;
     }
 
     Type &Type::operator=(const Type &type) {
         id = type.id;
+        constant = type.constant;
 
         if (type.className) {
             className = type.className.value();
@@ -120,6 +122,10 @@ namespace X {
     }
 
     std::ostream &operator<<(std::ostream &out, const Type &type) {
+        if (type.isConst()) {
+            out << "const ";
+        }
+
         switch (type.getTypeID()) {
             case Type::TypeID::INT:
                 return out << "int";

diff --git a/src/type.h b/src/type.h
@@ -48,6 +48,7 @@ namespace X {
         TypeID id;
         std::optional<std::string> className;
         Type *subtype = nullptr;
+        bool constant;
 
         Type(TypeID id) : id(id) {}
 
@@ -69,6 +70,8 @@ namespace X {
         TypeID getTypeID() const { return id; }
         const std::string &getClassName() const { return className.value(); }
         Type *getSubtype() const { return subtype; }
+        void makeConst() { constant = true; }
+        bool isConst() const { return constant; }
 
         bool is(TypeID typeId) const { return id == typeId; }
 

diff --git a/tests/statement_test.cpp b/tests/statement_test.cpp
@@ -1,6 +1,7 @@
 #include "compiler_test_helper.h"
 
 #include "codegen/codegen.h"
+#include "pipes/type_inferrer.h"
 
 class StatementTest : public CompilerTest {
 };
@@ -75,3 +76,58 @@ fn main() void {
 }
 )code", "3");
 }
+
+TEST_F(StatementTest, consts) {
+    checkProgram(R"code(
+const auto x = 10
+
+fn main() void {
+    const int y = 20
+
+    println(x + y)
+}
+)code", "30");
+}
+
+TEST_P(StatementTest, modifyConst) {
+    auto [code, exceptionMessage] = GetParam();
+
+    try {
+        compiler.compile(code);
+        FAIL() << "expected ModifyConstException";
+    } catch (const Pipes::ModifyConstException &e) {
+        ASSERT_EQ(e.what(), exceptionMessage);
+    }
+}
+
+INSTANTIATE_TEST_SUITE_P(Code, StatementTest, testing::Values(
+        std::make_pair(
+                R"code(
+const auto x = 10
+
+fn main() void {
+    x = 20
+}
+)code", "can't modify const"),
+        std::make_pair(
+                R"code(
+fn main() void {
+    const int x = 10
+    x = 20
+}
+)code", "can't modify const"),
+        std::make_pair(
+                R"code(
+fn main() void {
+    const auto a = [1, 2, 3]
+    a[] = 4
+}
+)code", "can't modify const"),
+        std::make_pair(
+                R"code(
+fn main() void {
+    const auto a = [1, 2, 3]
+    a[1] = 4
+}
+)code", "can't modify const")
+));
diff --git a/tests/tour_test.cpp b/tests/tour_test.cpp
@@ -81,7 +81,8 @@ fn types() void {
     []Foo arr = [new Foo(), new Foo()]
 }
 
-auto PI = 3.14 // globals
+auto qux = 123 // globals
+const auto PI = 3.14 // consts
 
 fn flow() void {
     // will print "then"