Port and integrate the irregexp engine from V8

tests/language/regex/invalid-range-in-class_test.dart

+// 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() {
+  description(
+  "This page tests invalid character ranges in character classes."
+  );
+
+  // These test a basic range / non range.
+  shouldBe(new RegExp(r"[a-c]+").firstMatch("-acbd"), ["acb"]);
+  shouldBe(new RegExp(r"[a\-c]+").firstMatch("-acbd"), ["-ac"]);
+
+  // A reverse-range is invalid.
+  assertThrows(() => new RegExp(r"[c-a]+").firstMatch("-acbd"));
+
+  // A character-class in a range is invalid, according to ECMA-262, but we allow it.
+  shouldBe(new RegExp(r"[\d-x]+").firstMatch("1-3xy"), ["1-3x"]);
+  shouldBe(new RegExp(r"[x-\d]+").firstMatch("1-3xy"), ["1-3x"]);
+  shouldBe(new RegExp(r"[\\d-\d]+").firstMatch("1-3xy"), ["1-3"]);
+
+  // Whilst we break with ECMA-262's definition of CharacterRange, we do comply with
+  // the grammar, and as such in the following regex a-z cannot be matched as a range.
+  shouldBe(new RegExp(r"[\d-a-z]+").firstMatch("az1-3y"), ["az1-3"]);
+
+  // An escaped hypen should not be confused for an invalid range.
+  shouldBe(new RegExp(r"[\d\-x]+").firstMatch("1-3xy"), ["1-3x"]);
+  shouldBe(new RegExp(r"[x\-\d]+").firstMatch("1-3xy"), ["1-3x"]);
+  shouldBe(new RegExp(r"[\d\-\d]+").firstMatch("1-3xy"), ["1-3"]);
+
+  // A hyphen after a character-class is not invalid.
+  shouldBe(new RegExp(r"[\d-]+").firstMatch("1-3xy"), ["1-3"]);
+}