Fix type test for callable objects (issue 7338).

tests/language/callable_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.
+
+class X {
+  call() => 42;
+}
+
+class Y {
+  call(int x) => 87;
+}
+
+typedef F(int x);
+typedef G(String y);
+
+main() {
+  X x = new X();
+  Function f = x;  // Should pass checked mode test
+  Y y = new Y();
+  Function g = y;  // Should pass checked mode test
+  F f0 = y;  // Should pass checked mode test
+  F f1 = x;  /// 00: dynamic type error, static type warning
+  G g0 = y;  /// 01: dynamic type error, static type warning
+}
+