Report an error if a const constructor calls a non-const constructor.

tests/language/const_constructor_mixin2_test.dart

+// Copyright (c) 2013, 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 Mixin {
+  var nonFinalField;
+}
+
+class A {
+  const A(foo);
+}
+
+class B extends A with Mixin {
+  const B(foo) : super(foo);
+}
+
+main() {
+  var a = const B(42);  /// 01: compile-time error

[floitsch, 2013/07/19 11:59:45]

I would prefer this error on the mixin line:

class B extends A
   with Mixin  /// 01: compile-time-error
   {
  const B(foo) : super(foo);
}

main() {
  var a = const B(42);
  a.nonFinalField = 54;  /// 01: continued
}

[ngeoffray, 2013/07/19 12:04:06]

Done.

[Lasse Reichstein Nielsen, 2013/07/19 12:19:54]

Actually, the error is in line 14, because super(foo) is not a const
constructor.

[ngeoffray, 2013/07/19 12:39:40]

What I like about Florian's suggestion is that the 'none' version of the
multitest runs with a const call.

+  a.nonFinalField = 54; /// 01: continued
+}