Implement function proxies (except for their use as constructors).

src/messages.js

 // Copyright 2006-2008 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 176 matching lines @@
       reduce_no_initial:            ["Reduce of empty array with no initial value"],
       getter_must_be_callable:      ["Getter must be a function: ", "%0"],
       setter_must_be_callable:      ["Setter must be a function: ", "%0"],
       value_and_accessor:           ["Invalid property.  A property cannot both have accessors and be writable or have a value: ", "%0"],
       proto_object_or_null:         ["Object prototype may only be an Object or null"],
       property_desc_object:         ["Property description must be an object: ", "%0"],
       redefine_disallowed:          ["Cannot redefine property: ", "%0"],
       define_disallowed:            ["Cannot define property:", "%0", ", object is not extensible."],
       non_extensible_proto:         ["%0", " is not extensible"],
       handler_non_object:           ["Proxy.", "%0", " called with non-object as handler"],
+      trap_function_expected:       ["Proxy.", "%0", " called with non-function for ", "%1", " trap"],
       handler_trap_missing:         ["Proxy handler ", "%0", " has no '", "%1", "' trap"],
       handler_trap_must_be_callable: ["Proxy handler ", "%0", " has non-callable '", "%1", "' trap"],
       handler_returned_false:       ["Proxy handler ", "%0", " returned false for '", "%1", "' trap"],
       handler_returned_undefined:   ["Proxy handler ", "%0", " returned undefined for '", "%1", "' trap"],
       proxy_prop_not_configurable:  ["Trap ", "%1", " of proxy handler ", "%0", " returned non-configurable descriptor for property ", "%2"],
       proxy_non_object_prop_names:  ["Trap ", "%1", " returned non-object ", "%0"],
       proxy_repeated_prop_name:     ["Trap ", "%1", " returned repeated property name ", "%2"],
       invalid_weakmap_key:          ["Invalid value used as weak map key"],
       // RangeError
       invalid_array_length:         ["Invalid array length"],
@@ skipping 913 matching lines @@
     else throw e;
   }
 }
 
 
 InstallFunctions($Error.prototype, DONT_ENUM, ['toString', errorToString]);
 
 // Boilerplate for exceptions for stack overflows. Used from
 // Isolate::StackOverflow().
 const kStackOverflowBoilerplate = MakeRangeError('stack_overflow', []);