Fixed a few typos.

dart/frog/leg/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);
 }
 
 class TreeElementMapping implements TreeElements {
@@ skipping 736 matching lines @@
     visit(node.thenPart);
     visit(node.elsePart);
   }
 
   static bool isLogicalOperator(Identifier op) {
     String str = op.source.stringValue;
     return (str === '&&' || str == '||' || str == '!');
   }
 
   Element resolveSend(Send node) {
-    if (node.receiver === null || (node.selector.asIdentifier() !== null &&
-                                   node.selector.asIdentifier().isThis())) {
+    if (node.receiver === null) {
       return node.selector.accept(this);
     }
     var oldCategory = allowedCategory;
     allowedCategory |=
       ElementCategory.CLASS | ElementCategory.PREFIX | ElementCategory.SUPER;
     Element resolvedReceiver = visit(node.receiver);
     allowedCategory = oldCategory;
 
     Element target;
     SourceString name = node.selector.asIdentifier().source;
-    if (node.isSuperCall) {
+    if (name.stringValue === 'this') {
+      error(node.selector, MessageKind.GENERIC, ["expected an identifier"]);
+    } else if (node.isSuperCall) {
       if (isUserDefinableOperator(name.stringValue)) {
         name = Elements.constructOperatorName(const SourceString('operator'),
                                               name);
       }
       if (!inInstanceContext) {
         error(node.receiver, MessageKind.NO_INSTANCE_AVAILABLE, [name]);
         return null;
       }
       if (currentClass.supertype === null) {
         // This is just to guard against internal errors, so no need
         // for a real error message.
-        error(node.receiver, MessageKind.GENERIC, "Object has no superclass");
+        error(node.receiver, MessageKind.GENERIC, ["Object has no superclass"]);
       }
       target = currentClass.lookupSuperMember(name);
       // [target] may be null which means invoking noSuchMethod on
       // super.
     } else if (resolvedReceiver === null) {
       return null;
     } else if (resolvedReceiver.kind === ElementKind.CLASS) {
       ClassElement receiverClass = resolvedReceiver;
       target = receiverClass.ensureResolved(compiler).lookupLocalMember(name);
       if (target === null) {
@@ skipping 957 matching lines @@
 
   TopScope(LibraryElement library) : super(null, library);
   Element lookup(SourceString name) {
     return library.find(name);
   }
 
   Element add(Element element) {
     throw "Cannot add an element in the top scope";
   }
 }