Regexp: Fix rightContext in the lastMatchInfoOverride

src/regexp.js

 // Copyright 2012 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 325 matching lines @@
     var override = lastMatchInfoOverride;
     start_index = override[override.length - 2];
     subject = override[override.length - 1];
   }
   return SubString(subject, 0, start_index);
 }
 
 
 function RegExpGetRightContext() {
   var start_index;
-  var subject;
+  var subject, pattern;

[Michael Starzinger, 2012/04/12 12:10:28]

The "pattern" variable could be moved into the else block.

   if (!lastMatchInfoOverride) {
     start_index = lastMatchInfo[CAPTURE1];
     subject = LAST_SUBJECT(lastMatchInfo);
   } else {
     var override = lastMatchInfoOverride;
     subject = override[override.length - 1];
-    start_index = override[override.length - 2] + subject.length;
+    pattern = override[override.length - 3];

[Lasse Reichstein Nielsen, 2012/04/13 06:59:52]

I don't think this is correct in all cases.

The override has the same format as the parameters to a function argument of
String.prototype.replace. I.e., it's 
[match, captures*, match-position, subject].

So 'pattern' should probably be called 'match', and it should be read as
override[0], not override[override.length - 3], in the cases where there are
captures.

You might want to consider making macros like

 macro OVERRIDE_MATCH(override) = ((override)[0]);
 macro OVERRIDE_POS(override) = ((override)[(override).length - 2]);
 macro OVERRIDE_SUBJECT(override) = ((override)[(override).length - 1]);
 macro OVERRIDE_CAPTURE(override, index) = ((override)[(index) + 1]);

(if for nothing else, it's documentation :)

+    start_index = override[override.length - 2] + pattern.length;
   }
   return SubString(subject, start_index, subject.length);
 }
 
 
 // The properties $1..$9 are the first nine capturing substrings of the last
 // successful match, or ''.  The function RegExpMakeCaptureGetter will be
 // called with indices from 1 to 9.
 function RegExpMakeCaptureGetter(n) {
   return function() {
@@ skipping 110 matching lines @@
                                     NoOpSetter, DONT_ENUM | DONT_DELETE);
 
   for (var i = 1; i < 10; ++i) {
     %DefineOrRedefineAccessorProperty($RegExp, '$' + i,
                                       RegExpMakeCaptureGetter(i), NoOpSetter,
                                       DONT_DELETE);
   }
 }
 
 SetUpRegExp();