Remove string constants from Types class.

dart/lib/compiler/implementation/resolver.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.
 
 interface TreeElements {
   Element operator[](Node node);
   Selector getSelector(Send send);
   Type getType(TypeAnnotation annotation);
 }
 
@@ skipping 349 matching lines @@
                              bool isSuperCall,
                              bool isImplicitSuperCall,
                              SourceString constructorName,
                              Selector selector,
                              Node diagnosticNode) {
     ClassElement lookupTarget = constructor.enclosingElement;
     bool validTarget = true;
     FunctionElement result;
     if (isSuperCall) {
       // Calculate correct lookup target and constructor name.
-      if (lookupTarget.name == Types.OBJECT) {
+      if (lookupTarget === visitor.compiler.objectClass) {
         error(diagnosticNode, MessageKind.SUPER_INITIALIZER_IN_OBJECT);
       } else {
         lookupTarget = lookupTarget.supertype.element;
       }
     }
 
     // Lookup constructor and try to match it to the selector.
     ResolverTask resolver = visitor.compiler.resolver;
     final SourceString className = lookupTarget.name;
     result = lookupTarget.lookupConstructor(className, constructorName);
@@ skipping 215 matching lines @@
 class TypeResolver {
   final Compiler compiler;
   TypeResolver(this.compiler);
 
   Element resolveTypeName(Scope context, TypeAnnotation node) {
     Identifier typeName = node.typeName.asIdentifier();
     Send send = node.typeName.asSend();
     if (send !== null) {
       typeName = send.selector;
     }
-    if (typeName.source == Types.VOID) {
+    if (typeName.source.stringValue === 'void') {
       return compiler.types.voidType.element;
     } else if (send !== null) {
       Element e = context.lookup(send.receiver.asIdentifier().source);
       if (e !== null && e.kind === ElementKind.PREFIX) {
         // The receiver is a prefix. Lookup in the imported members.
         PrefixElement prefix = e;
         return prefix.lookupLocalMember(typeName.source);
       } else if (e !== null && e.kind === ElementKind.CLASS) {
         // The receiver is the class part of a named constructor.
         return e;
@@ skipping 969 matching lines @@
     // Find super type.
     Type supertype = visit(node.superclass);
     if (supertype !== null && supertype.element.isExtendable()) {
       classElement.supertype = supertype;
       if (isBlackListed(supertype)) {
         error(node.superclass, MessageKind.CANNOT_EXTEND, [supertype]);
       }
     } else if (supertype !== null) {
       error(node.superclass, MessageKind.TYPE_NAME_EXPECTED);
     }
-    if (classElement.name != Types.OBJECT && classElement.supertype === null) {
-      ClassElement objectElement = context.lookup(Types.OBJECT);
-      if (objectElement !== null && !objectElement.isResolved) {
+    final objectElement = compiler.objectClass;
+    if (classElement !== objectElement && classElement.supertype === null) {
+      if (objectElement === null) {
+        compiler.internalError("Internal error: cannot resolve Object",
+                               node: node);
+      } else if (!objectElement.isResolved) {
         compiler.resolver.toResolve.add(objectElement);
-      } else if (objectElement === null){
-        error(node, MessageKind.CANNOT_RESOLVE_TYPE, [Types.OBJECT]);
       }
       classElement.supertype = new InterfaceType(objectElement);
     }
     if (node.defaultClause !== null) {
       classElement.defaultClass = visit(node.defaultClause);
     }
     for (Link<Node> link = node.interfaces.nodes;
          !link.isEmpty();
          link = link.tail) {
       Type interfaceType = visit(link.head);
@@ skipping 481 matching lines @@
 
   TopScope(LibraryElement library) : super(null, library);
   Element lookup(SourceString name) {
     return library.find(name);
   }
 
   Element add(Element newElement) {
     throw "Cannot add an element in the top scope";
   }
 }