Support for generic type variables and unresolved types added.

lib/compiler/implementation/dart_backend/backend.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.
 
 class DartBackend extends Backend {
   final List<CompilerTask> tasks;
   final UnparseValidator unparseValidator;
 
   Map<Element, TreeElements> get resolvedElements() =>
       compiler.enqueuer.resolution.resolvedElements;
@@ skipping 139 matching lines @@
       typedefs.add(typeElement);
       new ReferencedElementCollector(
           compiler, typeElement, new TreeElementMapping(), typedefs, classes)
       .collect();
     }
     if (typeElement.isClass()) classes.add(typeElement);
     typeAnnotation.visitChildren(this);
   }
 
   void collect() {
-    element.parseNode(compiler).accept(this);
+    compiler.withCurrentElement(element, () {
+      element.parseNode(compiler).accept(this);
+    });
   }
 }