Add tests for generic methods in strong mode

tests/language_strong/generic_methods_dynamic_test.dart

+// Copyright (c) 2017, 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.
+
+// Test that if the type of a parameter of a generic method is a type parameter,
+// the type of the passed argument is checked (01) at compile time
+// if the receiver is given via an interface-type variable, and (02) at runtime
+// if the receiver is dynamic.
+
+library generic_methods_dynamic_test;
+
+import "package:expect/expect.dart";
+
+class A {}
+
+class B {}
+
+class C {
+  T foo<T>(T t) => t;
+  List<T> bar<T>(Iterable<T> t) => <T>[t.first];
+}
+
+main() {
+  B b = new B();
+  C c = new C();
+  dynamic obj = c;
+
+  c.foo<A>(b); /// 01: compile-time error
+  obj.foo<A>(b); /// 02: runtime error
+
+  c.bar<A>(<B>[new B()]); /// 03: compile-time error
+  obj.bar<A>(<B>[new B()]); /// 04: runtime error
+
+  Expect.equals(c.foo<B>(b), b); /// 05: ok
+  Expect.equals(obj.foo<B>(b), b); /// 05: continued
+
+  dynamic x = c.bar<B>(<B>[new B()]); /// 05: continued
+  Expect.isTrue(x is List<B>); /// 05: continued
+  Expect.equals(x.length, 1); /// 05: continued
+
+  dynamic y = obj.bar<B>(<B>[new B()]); /// 05: continued
+  Expect.isTrue(y is List<B>); /// 05: continued
+  Expect.equals(y.length, 1); /// 05: continued
+}