Add web compat workarounds for ES2015 RegExp semantics

src/js/regexp.js

 // Copyright 2012 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.
 
 (function(global, utils) {
 
 %CheckIsBootstrapping();
 
 // -------------------------------------------------------------------
 // Imports
@@ skipping 252 matching lines @@
     regexp_val =
       new GlobalRegExp(
           %_SubString(REGEXP_SOURCE(regexp), 2, REGEXP_SOURCE(regexp).length),
           (REGEXP_IGNORE_CASE(regexp) ? REGEXP_MULTILINE(regexp) ? "im" : "i"
                                       : REGEXP_MULTILINE(regexp) ? "m" : ""));
   }
   return regexp_val;
 }
 
 
+const kRegExpPrototypeToString = 12;
+
 function RegExpToString() {
   if (!IS_REGEXP(this)) {
+    // RegExp.prototype.toString() returns '/(?:)/' as a compatibility fix;
+    // a UseCounter is incremented to track it.
+    // TODO(littledan): Remove this workaround or standardize it
+    if (this === GlobalRegExpPrototype) {
+      %IncrementUseCounter(kRegExpPrototypeToString);
+      return '/(?:)/';
+    }
     throw MakeTypeError(kIncompatibleMethodReceiver,
                         'RegExp.prototype.toString', this);
   }
   var result = '/' + REGEXP_SOURCE(this) + '/';
   if (REGEXP_GLOBAL(this)) result += 'g';
   if (REGEXP_IGNORE_CASE(this)) result += 'i';
   if (REGEXP_MULTILINE(this)) result += 'm';
   if (REGEXP_UNICODE(this)) result += 'u';
   if (REGEXP_STICKY(this)) result += 'y';
   return result;
@@ skipping 199 matching lines @@
     throw MakeTypeError(kRegExpNonRegExp, "RegExp.prototype.source");
   }
   return REGEXP_SOURCE(this);
 }
 %FunctionSetName(RegExpGetSource, "RegExp.prototype.source");
 %SetNativeFlag(RegExpGetSource);
 
 // -------------------------------------------------------------------
 
 %FunctionSetInstanceClassName(GlobalRegExp, 'RegExp');
-%FunctionSetPrototype(GlobalRegExp, new GlobalObject());
+const GlobalRegExpPrototype = new GlobalObject();

[Yang, 2015/12/22 06:31:22]

Regexp.js is one of the remaining native scripts that are not in strict mode.
Not sure whether we want legacy const here.

[Dan Ehrenberg, 2015/12/22 07:20:42]

I think this makes sense, since it'll be a clean upgrade to ES2015 const
semantics.

+%FunctionSetPrototype(GlobalRegExp, GlobalRegExpPrototype);
 %AddNamedProperty(
     GlobalRegExp.prototype, 'constructor', GlobalRegExp, DONT_ENUM);
 %SetCode(GlobalRegExp, RegExpConstructor);
 
 utils.InstallFunctions(GlobalRegExp.prototype, DONT_ENUM, [
   "exec", RegExpExecJS,
   "test", RegExpTest,
   "toString", RegExpToString,
   "compile", RegExpCompileJS,
   matchSymbol, RegExpMatch,
@@ skipping 58 matching lines @@
 // Exports
 
 utils.Export(function(to) {
   to.RegExpExec = DoRegExpExec;
   to.RegExpExecNoTests = RegExpExecNoTests;
   to.RegExpLastMatchInfo = RegExpLastMatchInfo;
   to.RegExpTest = RegExpTest;
 });
 
 })