Migrate test block 113 to Dart 2.0.

tests/language_strong/generic_deep_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";
-
-// Dart test for deeply nested generic types.
-
-/** A natural number aka Peano number. */
-abstract class N {
-  N add1();
-  N sub1();
-}
-
-/** Zero element. */
-class Z implements N {
-  Z();
-  N add1() {
-    return new S<Z>(this);
-  }
-
-  N sub1() {
-    throw "Error: sub1(0)";
-  }
-}
-
-/** Successor element. */
-class S<K> implements N {
-  N before;
-  S(this.before);
-  N add1() {
-    return new S<S<K>>(this);
-  }
-
-  N sub1() {
-    // It would be super cool if this could be "new K()".
-    return before;
-  }
-}
-
-N NFromInt(int x) {
-  if (x == 0)
-    return new Z();
-  else
-    return NFromInt(x - 1).add1();
-}
-
-int IntFromN(N x) {
-  if (x is Z) return 0;
-  if (x is S) return IntFromN(x.sub1()) + 1;
-  throw "Error";
-}
-
-bool IsEven(N x) {
-  if (x is Z) return true;
-  if (x is S<Z>) return false;
-  if (x is S<S>) return IsEven(x.sub1().sub1());
-  throw "Error in IsEven";
-}
-
-main() {
-  Expect.isTrue(NFromInt(0) is Z);
-  Expect.isTrue(NFromInt(1) is S<Z>);
-  Expect.isTrue(NFromInt(2) is S<S<Z>>);
-  Expect.isTrue(NFromInt(3) is S<S<S<Z>>>);
-  Expect.isTrue(NFromInt(10) is S<S<S<S<S<S<S<S<S<S<Z>>>>>>>>>>);
-
-  // Negative tests.
-  Expect.isTrue(NFromInt(0) is! S);
-  Expect.isTrue(NFromInt(1) is! Z);
-  Expect.isTrue(NFromInt(1) is! S<S>);
-  Expect.isTrue(NFromInt(2) is! Z);
-  Expect.isTrue(NFromInt(2) is! S<Z>);
-  Expect.isTrue(NFromInt(2) is! S<S<S>>);
-
-  // Greater-than tests
-  Expect.isTrue(NFromInt(4) is S<S>); //            4 >= 2
-  Expect.isTrue(NFromInt(4) is S<S<S>>); //         4 >= 3
-  Expect.isTrue(NFromInt(4) is S<S<S<S>>>); //      4 >= 4
-  Expect.isTrue(NFromInt(4) is! S<S<S<S<S>>>>); //  4 < 5
-
-  Expect.isTrue(IsEven(NFromInt(0)));
-  Expect.isFalse(IsEven(NFromInt(1)));
-  Expect.isTrue(IsEven(NFromInt(2)));
-  Expect.isFalse(IsEven(NFromInt(3)));
-  Expect.isTrue(IsEven(NFromInt(4)));
-
-  Expect.equals(0, IntFromN(NFromInt(0)));
-  Expect.equals(1, IntFromN(NFromInt(1)));
-  Expect.equals(2, IntFromN(NFromInt(2)));
-  Expect.equals(50, IntFromN(NFromInt(50)));
-}