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

src/macros.py

 # Copyright 2006-2009 the V8 project authors. All rights reserved.
 # Redistribution and use in source and binary forms, with or without
 # modification, are permitted provided that the following conditions are
 # met:
 #
 #     * Redistributions of source code must retain the above copyright
 #       notice, this list of conditions and the following disclaimer.
 #     * Redistributions in binary form must reproduce the above
 #       copyright notice, this list of conditions and the following
 #       disclaimer in the documentation and/or other materials provided
@@ skipping 110 matching lines @@
 
 # Macro for ECMAScript 5 queries of the type:
 # "Type(O) is object."
 # This is the same as being either a function or an object in V8 terminology
 # (including proxies).
 # In addition, an undetectable object is also included by this.
 macro IS_SPEC_OBJECT(arg)   = (%_IsSpecObject(arg));
 
 # Macro for ECMAScript 5 queries of the type:
 # "IsCallable(O)"
-# We assume here that this is the same as being either a function or a function
-# proxy. That ignores host objects with [[Call]] methods, but in most situations
-# we cannot handle those anyway.
-macro IS_SPEC_FUNCTION(arg) = (%_ClassOf(arg) === 'Function');
+macro IS_CALLABLE(arg) = (typeof(arg) === 'function');
 
 # Macro for ES6 CheckObjectCoercible
 # Will throw a TypeError of the form "[functionName] called on null or undefined".
 macro CHECK_OBJECT_COERCIBLE(arg, functionName) = if (IS_NULL(%IS_VAR(arg)) || IS_UNDEFINED(arg)) throw MakeTypeError(kCalledOnNullOrUndefined, functionName);
 
 # Indices in bound function info retrieved by %BoundFunctionGetBindings(...).
 define kBoundFunctionIndex = 0;
 define kBoundThisIndex = 1;
 define kBoundArgumentsStartIndex = 2;
 
@@ skipping 156 matching lines @@
 define NOT_FOUND = -1;
 
 # Check whether debug is active.
 define DEBUG_IS_ACTIVE = (%_DebugIsActive() != 0);
 macro DEBUG_IS_STEPPING(function) = (%_DebugIsActive() != 0 && %DebugCallbackSupportsStepping(function));
 macro DEBUG_PREPARE_STEP_IN_IF_STEPPING(function) = if (DEBUG_IS_STEPPING(function)) %DebugPrepareStepInIfStepping(function);
 
 # SharedFlag equivalents
 define kNotShared = false;
 define kShared = true;