Migrate language block 46 - canonical_const ... char_escape.

tests/language_strong/cascade_2_test.dart

-// Copyright (c) 2012, 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 "package:expect/expect.dart";
-
-// Test cascades, issues 7494 (vm), 7689 (dart2js).
-
-main() {
-  var a = new Element(null);
-  Expect.equals(1, a.path0.length);
-  Expect.equals(a, a.path0[0]);
-
-  // Issue 7693: e0 ? e1 : e2..f() parses as (e0 ? e1 : e2)..f().
-  Expect.equals(2, a.path1.length);
-  Expect.equals(a, a.path1[0]);
-  Expect.equals(a, a.path1[1]);
-
-  Expect.equals(1, a.path2.length); // NPE.
-
-  var b = new Element(a);
-  Expect.equals(2, b.path0.length);
-  Expect.equals(a, b.path0[0]);
-  Expect.equals(b, b.path0[1]);
-
-  Expect.equals(3, b.path1.length);
-  Expect.equals(a, b.path1[0]);
-  Expect.equals(a, b.path1[1]);
-  Expect.equals(b, b.path1[2]);
-
-  Expect.equals(2, b.path2.length); // NPE.
-}
-
-class Element {
-  final Element parent;
-
-  Element(this.parent);
-
-  List<Element> get path0 {
-    if (parent == null) {
-      return <Element>[this];
-    } else {
-      return parent.path0..add(this);
-    }
-  }
-
-  List<Element> get path1 {
-    return (parent == null) ? <Element>[this] : parent.path1
-      ..add(this);
-  }
-
-  List<Element> get path2 {
-    return (parent == null) ? <Element>[this] : (parent.path2..add(this));
-  }
-}