Port and integrate the irregexp engine from V8

tests/language/regex/toString_test.dart

Index: tests/language/regex/toString_test.dart
diff --git a/tests/language/regex/toString_test.dart b/tests/language/regex/toString_test.dart
new file mode 100644
index 0000000000000000000000000000000000000000..ba041ce1fa87006800741de5f00351e5dc4b7b90
--- /dev/null
+++ b/tests/language/regex/toString_test.dart
@@ -0,0 +1,50 @@
+// Copyright (c) 2014, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+import 'util.dart';
+import 'package:expect/expect.dart';
+
+void main() {
+  dynamic testForwardSlash(pattern, _string)
+  {
+      var string = _string;
+
+      var re1 = new RegExp(pattern);
+
+      return re1.hasMatch(string);
+  }
+
+  dynamic testLineTerminator(pattern)
+  {
+      var re1 = new RegExp(pattern);
+
+      return new RegExp(r"\n|\r|\u2028|\u2029").hasMatch(re1.toString());
+  }
+
+  // These strings are equivalent, since the '\' is identity escaping the '/' at the string level.
+  shouldBeTrue(testForwardSlash("^/\$", "/"));
+  shouldBeTrue(testForwardSlash("^\/\$", "/"));
+  // This string passes "^\/$" to the RegExp, so the '/' is escaped in the re!
+  shouldBeTrue(testForwardSlash("^\\/\$", "/"));
+  // These strings pass "^\\/$" and "^\\\/$" respectively to the RegExp, giving one '\' to match.
+  shouldBeTrue(testForwardSlash("^\\\\/\$", "\\/"));
+  shouldBeTrue(testForwardSlash("^\\\\\\/\$", "\\/"));
+  // These strings match two backslashes (the second with the '/' escaped).
+  shouldBeTrue(testForwardSlash("^\\\\\\\\/\$", "\\\\/"));
+  shouldBeTrue(testForwardSlash("^\\\\\\\\\\/\$", "\\\\/"));
+  // Test that nothing goes wrongif there are multiple forward slashes!
+  shouldBeTrue(testForwardSlash("x/x/x", "x/x/x"));
+  shouldBeTrue(testForwardSlash("x\\/x/x", "x/x/x"));
+  shouldBeTrue(testForwardSlash("x/x\\/x", "x/x/x"));
+  shouldBeTrue(testForwardSlash("x\\/x\\/x", "x/x/x"));
+
+  shouldBeFalse(testLineTerminator("\\n"));
+  shouldBeFalse(testLineTerminator("\\\\n"));
+  shouldBeFalse(testLineTerminator("\\r"));
+  shouldBeFalse(testLineTerminator("\\\\r"));
+  shouldBeFalse(testLineTerminator("\\u2028"));
+  shouldBeFalse(testLineTerminator("\\\\u2028"));
+  shouldBeFalse(testLineTerminator("\\u2029"));
+  shouldBeFalse(testLineTerminator("\\\\u2029"));
+}