Add test.

tests/language/src/CompileTimeConstant7Test.dart

Index: tests/language/src/CompileTimeConstant7Test.dart
diff --git a/tests/language/src/CompileTimeConstant7Test.dart b/tests/language/src/CompileTimeConstant7Test.dart
new file mode 100644
index 0000000000000000000000000000000000000000..574f6974106017288ad11d2f358df468cb52f7ac
--- /dev/null
+++ b/tests/language/src/CompileTimeConstant7Test.dart
@@ -0,0 +1,14 @@
+// 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 A {
+  const A();
+  toString() => "a";
+}
+
+final a = const A();
+
+main() {
+  Expect.equals("a", a.toString());
+}