Refactor ConstantExpression/ConstantConstructor to use entities.

pkg/compiler/lib/src/constants/evaluation.dart

 // Copyright (c) 2015, 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.evaluation;
 
 import '../compiler.dart' show Compiler;
+import '../elements/elements.dart';
+import '../elements/entities.dart';
+import '../elements/resolution_types.dart';
+import '../elements/types.dart';
 import '../universe/call_structure.dart' show CallStructure;
+import 'constructors.dart';
 import 'expressions.dart';
 
 /// Environment used for evaluating constant expressions.
 abstract class Environment {
   // TODO(johnniwinther): Replace this with [CommonElements] and maybe
   // [Backend].
   Compiler get compiler;
 
   /// Read environments string passed in using the '-Dname=value' option.
   String readFromEnvironment(String name);
+
+  /// Returns the [ConstantExpression] for the value of the constant [local].
+  ConstantExpression getLocalConstant(Local local);
+
+  /// Returns the [ConstantExpression] for the value of the constant [field].
+  ConstantExpression getFieldConstant(FieldEntity field);
+
+  /// Returns the [ConstantConstructor] corresponding to the constant
+  /// [constructor].
+  ConstantConstructor getConstructorConstant(ConstructorEntity constructor);
+
+  /// Performs the substitution of the type arguments of [target] for their
+  /// corresponding type variables in [type].
+  InterfaceType substByContext(InterfaceType base, InterfaceType target);
 }
 
 /// The normalized arguments passed to a const constructor computed from the
 /// actual [arguments] and the [defaultValues] of the called construrctor.
 class NormalizedArguments {
   final Map<dynamic /*int|String*/, ConstantExpression> defaultValues;
   final CallStructure callStructure;
   final List<ConstantExpression> arguments;
 
   NormalizedArguments(this.defaultValues, this.callStructure, this.arguments);
@@ skipping 10 matching lines @@
 
   /// Returns the normalized [index]th positional argument.
   ConstantExpression getPositionalArgument(int index) {
     if (index >= callStructure.positionalArgumentCount) {
       // The positional argument is not provided.
       return defaultValues[index];
     }
     return arguments[index];
   }
 }