Use Feature directly in resolution.

pkg/compiler/lib/src/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.
 
 part of dart_backend;
 
 // TODO(ahe): This class is simply wrong.  This backend should use
 // elements when it can, not AST nodes.  Perhaps a [Map<Element,
 // TreeElements>] is what is needed.
 class ElementAst {
@@ skipping 341 matching lines @@
 
 class DartImpactTransformer extends ImpactTransformer {
   final DartBackend backend;
 
   DartImpactTransformer(this.backend);
 
   @override
   WorldImpact transformResolutionImpact(ResolutionImpact worldImpact) {
     TransformedWorldImpact transformed =
         new TransformedWorldImpact(worldImpact);
-    for (DartType typeLiteral in worldImpact.typeLiterals) {
-      if (typeLiteral.isInterfaceType) {
-        backend.usedTypeLiterals.add(typeLiteral.element);
+    for (TypeUse typeUse in worldImpact.typeUses) {
+      if (typeUse.kind == TypeUseKind.TYPE_LITERAL &&
+          typeUse.type.isInterfaceType) {
+        backend.usedTypeLiterals.add(typeUse.type.element);
       }
-    }
-    for (TypeUse typeUse in worldImpact.typeUses) {
       if (typeUse.kind == TypeUseKind.INSTANTIATION) {
         backend.registerPlatformMembers(typeUse.type,
             registerUse: transformed.registerDynamicUse);
       }
     }
     return transformed;
   }
 }
 
 class EmitterUnparser extends Unparser {
@@ skipping 170 matching lines @@
   }
 
   // TODO(johnniwinther): Remove this when values are computed from the
   // expressions.
   @override
   void copyConstantValues(DartConstantTask task) {
     constantCompiler.constantValueMap.addAll(
         task.constantCompiler.constantValueMap);
   }
 }