Add locations to diagnostics.

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 1474 matching lines @@
       error(node, MessageKind.NOT_A_TYPE, [node]);
       return null;
     } else {
       if (element.isClass()) {
         compiler.resolver.toResolve.add(element);
       }
       if (element.isTypeVariable()) {
         TypeVariableElement variableElement = element;
         return variableElement.type;
       } else if (element.isTypedef()) {
-        compiler.unimplemented('visitIdentifier for typedefs');
+        compiler.unimplemented('visitIdentifier for typedefs', node: node);
       } else {
         // TODO(ngeoffray): Use type variables.
         return element.computeType(compiler);
       }
     }
     return null;
   }
 
   Type visitSend(Send node) {
     Identifier prefix = node.receiver.asIdentifier();
@@ skipping 437 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";
   }
 }