LibJS: Move has_constructor() from NativeFunction to FunctionObject

At a later point this will indicate whether some FunctionObject "has a
[[Construct]] internal method" (separate from the current FunctionObject
call() / construct()), to help with a more spec-compliant implementation
of [[Call]] and [[Construct]].
This means that it is no longer relevant to just NativeFunction.

Userland/Libraries/LibJS/AST.cpp

@@ -181,7 +181,7 @@ Value NewExpression::execute(Interpreter& interpreter, GlobalObject& global_obje
     if (vm.exception())
         return {};
 
-    if (!callee_value.is_function() || (is<NativeFunction>(callee_value.as_object()) && !static_cast<NativeFunction&>(callee_value.as_object()).has_constructor())) {
+    if (!callee_value.is_function() || !callee_value.as_function().has_constructor()) {
         throw_type_error_for_callee(interpreter, global_object, callee_value, "constructor"sv);
         return {};
     }

Userland/Libraries/LibJS/Runtime/BoundFunction.h

@@ -23,6 +23,7 @@ public:
     virtual FunctionEnvironment* create_environment(FunctionObject&) override;
     virtual const FlyString& name() const override { return m_name; }
     virtual bool is_strict_mode() const override { return m_bound_target_function->is_strict_mode(); }
+    virtual bool has_constructor() const override { return true; }
 
     FunctionObject& bound_target_function() const { return *m_bound_target_function; }
     Value bound_this() const { return m_bound_this; }

Userland/Libraries/LibJS/Runtime/ECMAScriptFunctionObject.h

@@ -71,6 +71,8 @@ public:
     // This is for IsSimpleParameterList (static semantics)
     bool has_simple_parameter_list() const { return m_has_simple_parameter_list; }
 
+    virtual bool has_constructor() const override { return true; }
+
 protected:
     virtual bool is_strict_mode() const final { return m_strict; }
 

Userland/Libraries/LibJS/Runtime/FunctionObject.h

@@ -27,6 +27,8 @@ public:
 
     virtual bool is_strict_mode() const { return false; }
 
+    virtual bool has_constructor() const { return false; }
+
     // [[Realm]]
     virtual Realm* realm() const { return nullptr; }
 

Userland/Libraries/LibJS/Runtime/NativeFunction.h

@@ -23,12 +23,9 @@ public:
 
     virtual Value call() override;
     virtual Value construct(FunctionObject& new_target) override;
-
     virtual const FlyString& name() const override { return m_name; };
-    virtual bool has_constructor() const { return false; }
-
     virtual bool is_strict_mode() const override;
-
+    virtual bool has_constructor() const override { return false; }
     virtual Realm* realm() const override { return m_realm; }
 
 protected:

Userland/Libraries/LibJS/Runtime/ProxyObject.h

@@ -24,6 +24,7 @@ public:
     virtual Value construct(FunctionObject& new_target) override;
     virtual const FlyString& name() const override;
     virtual FunctionEnvironment* create_environment(FunctionObject&) override;
+    virtual bool has_constructor() const override { return true; }
 
     const Object& target() const { return m_target; }
     const Object& handler() const { return m_handler; }

Userland/Libraries/LibJS/Runtime/Value.cpp

@@ -237,14 +237,16 @@ FunctionObject const& Value::as_function() const
 // 7.2.4 IsConstructor ( argument ), https://tc39.es/ecma262/#sec-isconstructor
 bool Value::is_constructor() const
 {
+    // 1. If Type(argument) is not Object, return false.
     if (!is_function())
         return false;
-    if (is<NativeFunction>(as_object()))
-        return static_cast<const NativeFunction&>(as_object()).has_constructor();
-    if (is<BoundFunction>(as_object()))
-        return Value(&static_cast<const BoundFunction&>(as_object()).bound_target_function()).is_constructor();
-    // ECMAScriptFunctionObject
-    return true;
+
+    // 2. If argument has a [[Construct]] internal method, return true.
+    if (as_function().has_constructor())
+        return true;
+
+    // 3. Return false.
+    return false;
 }
 
 // 7.2.8 IsRegExp ( argument ), https://tc39.es/ecma262/#sec-isregexp