Handle type variables.

pkg/front_end/lib/src/fasta/builder/mixin_application_builder.dart

 // Copyright (c) 2016, 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.
 
 library fasta.mixin_application_builder;
 
+import '../errors.dart' show
+    internalError;
+
 import 'builder.dart' show
-    TypeBuilder;
+    TypeBuilder,
+    TypeDeclarationBuilder;
 
 import 'scope.dart' show
     Scope;
 
 abstract class MixinApplicationBuilder<T extends TypeBuilder>
     extends TypeBuilder {
   final T supertype;
   final List<T> mixins;
 
   MixinApplicationBuilder(this.supertype, this.mixins);
 
+  String get name => null;
+
   void resolveIn(Scope scope) {
     supertype.resolveIn(scope);
     for (T t in mixins) {
       t.resolveIn(scope);
     }
   }
 
+  void bind(TypeDeclarationBuilder builder) {
+    internalError("Internal error: can't bind a mixin application.");
+  }
+
   String get debugName => "MixinApplicationBuilder";
 
   StringBuffer printOn(StringBuffer buffer) {
     buffer.write(supertype);
     buffer.write(" with ");
     bool first = true;
     for (T t in mixins) {
       if (!first) buffer.write(", ");
       first = false;
       t.printOn(buffer);
     }
     return buffer;
   }
 }