Migrate test block 113 to Dart 2.0.

tests/language_2/generic_closure_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.
+// Dart test program for constructors and initializers.
+
+// Check that generic closures are properly instantiated.
+
+import 'package:expect/expect.dart';
+
+typedef T F<T>(T x);
+typedef R G<T, R>(T x);
+
+class C<T> {
+  get f => (T x) => x;
+  T g(T x) => x;
+}
+
+main() {
+  {
+    var c = new C<int>();
+    var f = c.f;
+    var g = c.g;
+    Expect.equals("(int) => int", f.runtimeType.toString()); //# 01: ok

[Jennifer Messerly, 2017/08/25 21:59:47]

FYI, I filed https://github.com/dart-lang/sdk/issues/30551 about the difference
in how our different implementations print types.

... I prefer DDC's slim arrow `->` slightly over VM's `=>` (it's less
ambiguous). But happy to change DDC if it means more consistency/easier porting
of tests. :)

[jcollins, 2017/08/29 15:41:06]

I slightly prefer the VM since it (at a limited glance) matches better with the
language syntax, but consistency would win over all options AFAIAC. :-D

For now, switched to DDC syntax since at least that way this test can pass on
one configuration.

+    Expect.equals("(int) => int", g.runtimeType.toString()); //# 01: ok

[Jennifer Messerly, 2017/08/25 21:59:47]

this should be (Object) -> int

because of covariant generics, we must reify the type of C<T>.g's parameter as
`Object`

[jcollins, 2017/08/29 15:41:05]

Done.

+    Expect.equals(21, f(21));
+    Expect.equals(14, g(14));
+    Expect.isTrue(f is Function);
+    Expect.isTrue(g is Function);
+    Expect.isTrue(f is F);
+    Expect.isTrue(g is F);
+    Expect.isTrue(f is F<int>);
+    Expect.isTrue(g is F<int>);
+    Expect.isTrue(f is! F<bool>);
+    Expect.isTrue(g is! F<bool>);
+    Expect.isTrue(f is G<int, int>);
+    Expect.isTrue(g is G<int, int>);
+    Expect.isTrue(f is! G<int, bool>);
+    Expect.isTrue(g is! G<int, bool>);

[Jennifer Messerly, 2017/08/25 21:59:48]

could we add these two tests, to illustrate the difference between `f` and `g`:

Expect.isTrue(f is! G<Object, int>);
Expect.isTrue(g is G<Object, int>);

[jcollins, 2017/08/29 15:41:05]

Done.

+  }
+
+  {
+    var c = new C<bool>();
+    var f = c.f;
+    var g = c.g;
+    Expect.equals("(bool) => bool", f.runtimeType.toString()); //# 01: ok
+    Expect.equals("(bool) => bool", g.runtimeType.toString()); //# 01: ok

[Jennifer Messerly, 2017/08/25 21:59:48]

this should be `(Object) -> bool`

[jcollins, 2017/08/29 15:41:05]

Done.

+    Expect.isTrue(f is F);
+    Expect.isTrue(g is F);
+    Expect.isTrue(f is! F<int>);
+    Expect.isTrue(g is! F<int>);
+    Expect.isTrue(f is F<bool>);
+    Expect.isTrue(g is F<bool>);
+  }
+
+  {
+    var c = new C();
+    var f = c.f;
+    var g = c.g;
+    Expect.equals("(dynamic) => dynamic", f.runtimeType.toString()); //# 01: ok
+    Expect.equals("(dynamic) => dynamic", g.runtimeType.toString()); //# 01: ok

[Jennifer Messerly, 2017/08/25 21:59:48]

this should be `(Object) -> dynamic`

[jcollins, 2017/08/29 15:41:05]

Done.

+    Expect.isTrue(f is F);
+    Expect.isTrue(g is F);
+    Expect.isTrue(f is! F<int>);
+    Expect.isTrue(g is! F<int>);
+    Expect.isTrue(f is! F<bool>);
+    Expect.isTrue(g is! F<bool>);
+  }
+}