Register mixin use from modelz.

pkg/compiler/lib/src/serialization/modelz.dart

 // Copyright (c) 2015, 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.
 
 /// Implementation of the element model used for deserialiation.
 ///
 /// These classes are created by [ElementDeserializer] triggered by the
 /// [Deserializer].
 
 library dart2js.serialization.modelz;
@@ skipping 925 matching lines @@
       ClassElement subclass, InterfaceType supertype, InterfaceType mixin)
       : this._subclass = subclass,
         this.supertype = supertype,
         this.interfaces = const Link<DartType>().prepend(mixin),
         this.name = "${supertype.name}+${mixin.name}";
 
   @override
   CompilationUnitElement get compilationUnit => _subclass.compilationUnit;
 
   @override
+  bool get isTopLevel => true;
+
+  @override
   bool get isUnnamedMixinApplication => true;
 
   Link<ConstructorElement> get constructors {
     if (_constructors == null) {
       LinkBuilder<ConstructorElement> builder =
           new LinkBuilder<ConstructorElement>();
       for (ConstructorElement definingConstructor in superclass.constructors) {
         if (definingConstructor.isGenerativeConstructor &&
             definingConstructor.memberName.isAccessibleFrom(library)) {
           builder.addLast(
@@ skipping 298 matching lines @@
   ConstantConstructor get constantConstructor => null;
 
   @override
   ConstructorElement get effectiveTarget => this;
 
   @override
   Element get enclosingElement => enclosingClass;
 
   @override
   FunctionSignature get functionSignature {
-    return _unsupported('functionSignature');
+    // TODO(johnniwinther): Ensure that the function signature (and with it the
+    // function type) substitutes type variables correctly.
+    return definingConstructor.functionSignature;
   }
 
   @override
   bool get hasFunctionSignature {
     return _unsupported('hasFunctionSignature');
   }
 
   @override
   ConstructorElement get immediateRedirectionTarget => null;
 
@@ skipping 826 matching lines @@
   }
 
   @override
   ElementKind get kind => ElementKind.PREFIX;
 
   @override
   Element lookupLocalMember(String memberName) {
     return _unsupported('lookupLocalMember');
   }
 }