[es6] Initial steps towards a correct implementation of IsCallable.

src/objects.h

Index: src/objects.h
diff --git a/src/objects.h b/src/objects.h
index 869253741702f8596dd45b59517bb816437b3414..0c9a6d20f0d29cd7e66f33d9f8f9b78d264f1a96 100644
--- a/src/objects.h
+++ b/src/objects.h
@@ -1016,7 +1016,11 @@ class Object {
   STRUCT_LIST(DECLARE_STRUCT_PREDICATE)
 #undef DECLARE_STRUCT_PREDICATE
 
+  // ES6, section 7.2.3 IsCallable.
+  INLINE(bool IsCallable() const);
+
   INLINE(bool IsSpecObject()) const;
+  // TODO(rossberg): IsSpecFunction should be removed in favor of IsCallable.
   INLINE(bool IsSpecFunction()) const;
   INLINE(bool IsTemplateInfo()) const;
   INLINE(bool IsNameDictionary() const);
@@ -1025,7 +1029,6 @@ class Object {
   INLINE(bool IsUnseededNumberDictionary() const);
   INLINE(bool IsOrderedHashSet() const);
   INLINE(bool IsOrderedHashMap() const);
-  bool IsCallable() const;
   static bool IsPromise(Handle<Object> object);
 
   // Oddball testing.
@@ -1107,6 +1110,9 @@ class Object {
   MUST_USE_RESULT static MaybeHandle<Object> GetMethod(
       Handle<JSReceiver> receiver, Handle<Name> name);
 
+  // ES6 section 12.5.6 The typeof Operator
+  static Handle<String> TypeOf(Isolate* isolate, Handle<Object> object);
+
   MUST_USE_RESULT static MaybeHandle<Object> GetProperty(
       LookupIterator* it, LanguageMode language_mode = SLOPPY);
 
@@ -5233,7 +5239,7 @@ class Map: public HeapObject {
   STATIC_ASSERT(kDescriptorIndexBitCount + kDescriptorIndexBitCount == 20);
   class DictionaryMap : public BitField<bool, 20, 1> {};
   class OwnsDescriptors : public BitField<bool, 21, 1> {};
-  class HasInstanceCallHandler : public BitField<bool, 22, 1> {};
+  class IsHiddenPrototype : public BitField<bool, 22, 1> {};
   class Deprecated : public BitField<bool, 23, 1> {};
   class IsUnstable : public BitField<bool, 24, 1> {};
   class IsMigrationTarget : public BitField<bool, 25, 1> {};
@@ -5268,7 +5274,7 @@ class Map: public HeapObject {
   // Tells whether the instance with this map should be ignored by the
   // Object.getPrototypeOf() function and the __proto__ accessor.
   inline void set_is_hidden_prototype();
-  inline bool is_hidden_prototype();
+  inline bool is_hidden_prototype() const;
 
   // Records and queries whether the instance has a named interceptor.
   inline void set_has_named_interceptor();
@@ -5291,6 +5297,11 @@ class Map: public HeapObject {
   inline void set_is_observed();
   inline bool is_observed();
 
+  // Tells whether the instance has a [[Call]] internal field.
+  // This property is implemented according to ES6, section 7.2.3.
+  inline void set_is_callable();
+  inline bool is_callable() const;
+
   inline void set_is_strong();
   inline bool is_strong();
   inline void set_is_extensible(bool value);
@@ -5466,8 +5477,6 @@ class Map: public HeapObject {
 
   inline bool owns_descriptors();
   inline void set_owns_descriptors(bool owns_descriptors);
-  inline bool has_instance_call_handler();
-  inline void set_has_instance_call_handler();
   inline void mark_unstable();
   inline bool is_stable();
   inline void set_migration_target(bool value);
@@ -5716,7 +5725,7 @@ class Map: public HeapObject {
 
   // Bit positions for bit field.
   static const int kHasNonInstancePrototype = 0;
-  static const int kIsHiddenPrototype = 1;
+  static const int kIsCallable = 1;
   static const int kHasNamedInterceptor = 2;
   static const int kHasIndexedInterceptor = 3;
   static const int kIsUndetectable = 4;
@@ -9298,7 +9307,7 @@ class JSProxy: public JSReceiver {
 class JSFunctionProxy: public JSProxy {
  public:
   // [call_trap]: The call trap.
-  DECL_ACCESSORS(call_trap, Object)
+  DECL_ACCESSORS(call_trap, JSReceiver)
 
   // [construct_trap]: The construct trap.
   DECL_ACCESSORS(construct_trap, Object)