RegExp: Fix caching to correctly set lastIndex.

test/mjsunit/regress/regress-52801.js

+// Copyright 2010 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:
+//
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+
+// Whenever we enter a with-scope, we copy the context. This in itself is fine
+// (contexts may escape), but when leaving a with-scope, we currently also copy
+// the context instead of reverting to the original. This does not work because
+// inner functions may already have been created using the original context. In
+// the failing test case below, the inner function is run in the original context
+// (where x is undefined), but the assignment to x after the with-statement is
+// run in the copied context:
+
+// RegExp caching doesn't set lastIndex correctly.
+// See http://code.google.com/p/chromium/issues/detail?id=52801
+
+var re = /a/g;
+
+var str = "bbbbabbbbabbbb";
+
+// Test
+
+re.test(str);
+assertEquals(5, re.lastIndex);
+
+re.lastIndex = 0;
+re.test(str);
+assertEquals(5, re.lastIndex);  // Fails if caching.
+
+re.lastIndex = 0;
+re.test(str);
+assertEquals(5, re.lastIndex);  // Fails if caching.
+
+// Exec
+
+re = /a/g;
+
+re.exec(str);
+assertEquals(5, re.lastIndex);
+
+re.lastIndex = 0;
+re.exec(str);
+assertEquals(5, re.lastIndex);  // Fails if caching.
+
+re.lastIndex = 0;
+re.exec(str);
+assertEquals(5, re.lastIndex);  // Fails if caching.
+
+