Implement new Function.prototype.toString and fix CreateDynamicFunction parsing

src/messages.h

 // Copyright 2006-2008 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // The infrastructure used for (localized) message reporting in V8.
 //
 // Note: there's a big unresolved issue about ownership of the data
 // structures used by this framework.
 
 #ifndef V8_MESSAGES_H_
@@ skipping 564 matching lines @@
   T(NotIsvar, "builtin %%IS_VAR: not a variable")                              \
   T(ParamAfterRest, "Rest parameter must be last formal parameter")            \
   T(PushPastSafeLength,                                                        \
     "Pushing % elements on an array-like of length % "                         \
     "is disallowed, as the total surpasses 2**53-1")                           \
   T(ElementAfterRest, "Rest element must be last element in array")            \
   T(BadSetterRestParameter,                                                    \
     "Setter function argument must not be a rest parameter")                   \
   T(ParamDupe, "Duplicate parameter name not allowed in this context")         \
   T(ParenthesisInArgString, "Function arg string contains parenthesis")        \
+  T(ExpectedEndOfParameters, "Expected arg string to end here")                \

[Dan Ehrenberg, 2016/12/06 00:32:13]

Aren't we talking about cases where someone effectively uses invalid syntax in
parameters for the function constructor? The exception text could reflect that
more directly.

[jwolfe, 2017/01/13 00:28:47]

I split the error into two different messages:

(function anonymous() { function f(
                    ^
SyntaxError: Arg string terminates parameters early

and:

(function anonymous(a=function(
                              ^^
SyntaxError: Unexpected end of arg string

I'm open to feedback on making these errors more clear.

   T(RuntimeWrongNumArgs, "Runtime function given wrong number of arguments")   \
   T(SingleFunctionLiteral, "Single function literal required")                 \
   T(SloppyFunction,                                                            \
     "In non-strict mode code, functions can only be declared at top level, "   \
     "inside a block, or as the body of an if statement.")                      \
   T(SpeciesNotConstructor,                                                     \
     "object.constructor[Symbol.species] is not a constructor")                 \
   T(StrictDelete, "Delete of an unqualified identifier in strict mode.")       \
   T(StrictEvalArguments, "Unexpected eval or arguments in strict mode")        \
   T(StrictFunction,                                                            \
@@ skipping 109 matching lines @@
   static Handle<String> GetMessage(Isolate* isolate, Handle<Object> data);
   static std::unique_ptr<char[]> GetLocalizedMessage(Isolate* isolate,
                                                      Handle<Object> data);
 };
 
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_MESSAGES_H_