Begin to compute constant expressions in resolution.

pkg/compiler/lib/src/constants/values.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.
 
 library dart2js.constants.values;
 
 import '../core_types.dart';
 import '../dart_types.dart';
 import '../dart2jslib.dart'
     show assertDebugMode;
@@ skipping 621 matching lines @@
 class ConstructedConstantValue extends ObjectConstantValue {
   final Map<FieldElement, ConstantValue> fields;
   final int hashCode;
 
   ConstructedConstantValue(InterfaceType type,
                            Map<FieldElement, ConstantValue> fields)
     : this.fields = fields,
       hashCode = Hashing.mapHash(fields, Hashing.objectHash(type)),
       super(type) {
     assert(type != null);
+    assert(!fields.containsValue(null));
   }
 
   bool get isConstructedObject => true;
 
   bool operator ==(var otherVar) {
     if (otherVar is !ConstructedConstantValue) return false;
     ConstructedConstantValue other = otherVar;
     if (hashCode != other.hashCode) return false;
     if (type != other.type) return false;
     if (fields.length != other.fields.length) return false;
@@ skipping 89 matching lines @@
 
   @override
   DartType getType(CoreTypes types) => const DynamicType();
 
   @override
   String toStructuredString() => 'NonConstant';
 
   @override
   String unparse() => '>>non-constant<<';
 }