Update tests to make latent errors explicit.

tests/language/compile_time_constant_e_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.
 
 import "package:expect/expect.dart";
 
 class A {
   final x;
   final y;
   final z;
   final t;
 
   const A([this.z = 99, tt = 100]) : y = 499, t = tt, x = 3;
   const A.n({this.z: 99, tt: 100}) : y = 499, t = tt, x = 3;
   const A.named({z, this.t}) : y = 400 + z, this.z = z, x = 3;
   const A.named2({t, z, y, x}) : x = t, y = z, z = y, t = x;
 
   toString() => "A $x $y $z $t";
 }
 
 const a1 = const A(99, 100);
-const a1n = const A.n(99, 100);

[Johnni Winther, 2016/07/05 10:34:16]

Unused in test.

 const a2 = const A.named(z: 99, t: 100);
 const a3 = const A.named2(t: 1, z: 2, y: 3, x: 4);
 const a4 = const A();
 const a5 = const A(99, 100);
 const a5n = const A.n(tt: 100, z: 99);
 const a6 = const A(1, 2);
 const a6n = const A.n(z: 1, tt: 2);
 const a7 = const A.named(z: 7);
 const a8 = const A.named2();
 const a9 = const A.named2(x: 4, y: 3, z: 2, t: 1);
@@ skipping 34 matching lines @@
   Expect.equals("A null null null null", a8.toString());
 
   Expect.isTrue(identical(a3, a9));
 
   Expect.equals(4, a10.x);
   Expect.equals(3, a10.y);
   Expect.equals(2, a10.z);
   Expect.equals(1, a10.t);
   Expect.equals("A 4 3 2 1", a10.toString());
 }