Add structural equality to ConstantExpression.

tests/compiler/dart2js/backend_dart/sexpr_unstringifier.dart

 // Copyright (c) 2014, 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.
 
 // SExpressionUnstringifier implements the inverse operation to
 // [SExpressionStringifier].
 
 library sexpr_unstringifier;
 
-import 'package:compiler/src/constants/expressions.dart'
-    show PrimitiveConstantExpression;
+import 'package:compiler/src/constants/expressions.dart';
 import 'package:compiler/src/constants/values.dart';
 import 'package:compiler/src/dart2jslib.dart' as dart2js
     show MessageKind;
 import 'package:compiler/src/dart_types.dart' as dart_types
     show DartType;
 import 'package:compiler/src/elements/elements.dart'
    show Entity, Element, Elements, Local, TypeVariableElement, ErroneousElement,
          TypeDeclarationElement, ExecutableElement, PublicName;
 import 'package:compiler/src/elements/modelx.dart'
     show ErroneousElementX, TypeVariableElementX;
@@ skipping 588 matching lines @@
 
   /// (Constant (constant))
   Constant parseConstant() {
     tokens.consumeStart(CONSTANT);
     tokens.consumeStart();
     Constant result;
     String tag = tokens.read();
     switch (tag) {
       case NULL:
         result = new Constant(
-            new PrimitiveConstantExpression(new NullConstantValue()));
+            new NullConstantExpression(new NullConstantValue()));
         break;
       case BOOL:
         String value = tokens.read();
         if (value == "true") {
           result = new Constant(
-              new PrimitiveConstantExpression(new TrueConstantValue()));
+              new BoolConstantExpression(true, new TrueConstantValue()));
         } else if (value == "false") {
           result = new Constant(
-              new PrimitiveConstantExpression(new FalseConstantValue()));
+              new BoolConstantExpression(false, new FalseConstantValue()));
         } else {
           throw "Invalid Boolean value '$value'.";
         }
         break;
       case STRING:
         List<String> strings = <String>[];
         do {
           strings.add(tokens.read());
         } while (tokens.current != ")");
         String string = strings.join(" ");
         assert(string.startsWith('"') && string.endsWith('"'));
+        String text = string.substring(1, string.length - 1);
         StringConstantValue value = new StringConstantValue(
-            new LiteralDartString(string.substring(1, string.length - 1)));
-        result = new Constant(new PrimitiveConstantExpression(value));
+            new LiteralDartString(text));
+        result = new Constant(new StringConstantExpression(text, value));
         break;
       case INT:
         String value = tokens.read();
         int intValue = int.parse(value, onError: (_) => null);
         if (intValue == null) {
           throw "Invalid int value 'value'.";
         }
-        result = new Constant(
-            new PrimitiveConstantExpression(new IntConstantValue(intValue)));
+        result = new Constant(new IntConstantExpression(
+            intValue, new IntConstantValue(intValue)));
         break;
       case DOUBLE:
         String value = tokens.read();
         double doubleValue = double.parse(value, (_) => null);
         if (doubleValue == null) {
           throw "Invalid double value '$value'.";
         }
-        result = new Constant(new PrimitiveConstantExpression(
-            new DoubleConstantValue(doubleValue)));
+        result = new Constant(new DoubleConstantExpression(
+            doubleValue, new DoubleConstantValue(doubleValue)));
         break;
       default:
         throw "Unexpected constant tag '$tag'.";
     }
     tokens.consumeEnd();
     tokens.consumeEnd();
     return result;
   }
 
   /// (CreateFunction (definition))
@@ skipping 48 matching lines @@
   /// (ReifyTypeVar type)
   ReifyTypeVar parseReifyTypeVar() {
     tokens.consumeStart(REIFY_TYPE_VAR);
 
     TypeVariableElement type = new DummyElement(tokens.read());
 
     tokens.consumeEnd();
     return new ReifyTypeVar(type);
   }
 }