LibJS: Throw TypeError when calling class constructor without 'new'

Libraries/LibJS/Runtime/ErrorTypes.h

@@ -36,6 +36,7 @@
     M(BigIntBadOperatorOtherType, "Cannot use {} operator with BigInt and other type")                                                  \
     M(BigIntIntArgument, "BigInt argument must be an integer")                                                                          \
     M(BigIntInvalidValue, "Invalid value for BigInt: {}")                                                                               \
+    M(ClassConstructorWithoutNew, "Class constructor {} must be called with 'new'")                                                     \
     M(ClassDoesNotExtendAConstructorOrNull, "Class extends value {} is not a constructor or null")                                      \
     M(Convert, "Cannot convert {} to {}")                                                                                               \
     M(ConvertUndefinedToObject, "Cannot convert undefined to object")                                                                   \

Libraries/LibJS/Runtime/ScriptFunction.cpp

@@ -110,7 +110,7 @@ LexicalEnvironment* ScriptFunction::create_environment()
     return environment;
 }
 
-Value ScriptFunction::call()
+Value ScriptFunction::execute_function_body()
 {
     auto& vm = this->vm();
 
@@ -150,13 +150,22 @@ Value ScriptFunction::call()
     return interpreter->execute_statement(global_object(), m_body, move(arguments), ScopeType::Function);
 }
 
+Value ScriptFunction::call()
+{
+    if (m_is_class_constructor) {
+        vm().throw_exception<TypeError>(global_object(), ErrorType::ClassConstructorWithoutNew, m_name);
+        return {};
+    }
+    return execute_function_body();
+}
+
 Value ScriptFunction::construct(Function&)
 {
     if (m_is_arrow_function) {
         vm().throw_exception<TypeError>(global_object(), ErrorType::NotAConstructor, m_name);
         return {};
     }
-    return call();
+    return execute_function_body();
 }
 
 JS_DEFINE_NATIVE_GETTER(ScriptFunction::length_getter)

Libraries/LibJS/Runtime/ScriptFunction.h

@@ -50,6 +50,8 @@ public:
     virtual const FlyString& name() const override { return m_name; };
     void set_name(const FlyString& name) { m_name = name; };
 
+    void set_is_class_constructor() { m_is_class_constructor = true; };
+
 protected:
     virtual bool is_strict_mode() const final { return m_is_strict; }
 
@@ -58,6 +60,8 @@ private:
     virtual LexicalEnvironment* create_environment() override;
     virtual void visit_children(Visitor&) override;
 
+    Value execute_function_body();
+
     JS_DECLARE_NATIVE_GETTER(length_getter);
     JS_DECLARE_NATIVE_GETTER(name_getter);
 
@@ -68,6 +72,7 @@ private:
     i32 m_function_length { 0 };
     bool m_is_strict { false };
     bool m_is_arrow_function { false };
+    bool m_is_class_constructor { false };
 };
 
 }