Begin writing tests of the runtime checks needed for Dart 2.0 soundness.

pkg/front_end/testcases/runtime_checks/call_through_this.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.
+
+/*@testedFeatures=checks*/
+library test;
+
+typedef F<T>(T x);
+
+class C<T> {
+  void f(T /*@checkFormal=semiSafe*/ x) {}
+  void g1(T /*@checkFormal=semiSafe*/ x) {
+    this.f(x);
+  }
+
+  void g2(T /*@checkFormal=semiSafe*/ x) {
+    f(x);
+  }
+
+  void g3(C<T> /*@checkFormal=semiSafe*/ c, T /*@checkFormal=semiSafe*/ x) {
+    c.f /*@checkCall=interface(semiTyped:0)*/ (x);
+  }
+
+  F<T> g4() => this.f;
+}
+
+class D extends C<int> {}
+
+class E extends C<num> {
+  void f(covariant int /*@checkFormal=unsafe*/ x) {}
+}
+
+test() {
+  var x = new D().g4() as F<Object>;
+  x /*@checkCall=interface(semiTyped:0)*/ ('hi');
+  new E().g1(1.5);
+}
+
+main() {}