Rebased and retested version of CL 1915123008.

pkg/compiler/lib/src/resolution/scope.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.
 
 library dart2js.resolution.scope;
 
 import '../dart_types.dart';
 import '../elements/elements.dart';
 
 abstract class Scope {
@@ skipping 40 matching lines @@
       variableReferencedInInitializer = true;
     }
     return null;
   }
 
   Element add(Element newElement) {
     throw "Cannot add element to VariableDefinitionScope";
   }
 }
 
-/**
- * [TypeDeclarationScope] defines the outer scope of a type declaration in
- * which the declared type variables and the entities in the enclosing scope are
- * available but where declared and inherited members are not available. This
- * scope is only used for class declarations during resolution of the
- * class hierarchy. In all other cases [ClassScope] is used.
- */
-class TypeDeclarationScope extends NestedScope {
-  final TypeDeclarationElement element;
+/// [TypeVariablesScope] defines the outer scope in a context where some type
+/// variables are declared and the entities in the enclosing scope are
+/// available, but where locally declared and inherited members are not
+/// available.
+abstract class TypeVariablesScope extends NestedScope {
+  List<DartType> get typeVariables;
 
-  TypeDeclarationScope(parent, this.element) : super(parent) {
+  TypeVariablesScope(Scope parent) : super(parent) {
     assert(parent != null);
   }
 
   Element add(Element newElement) {
     throw "Cannot add element to TypeDeclarationScope";
   }
 
   Element lookupTypeVariable(String name) {
-    List<DartType> typeVariables = element.typeVariables;
     for (TypeVariableType type in typeVariables) {
       if (type.name == name) {
         return type.element;
       }
     }
     return null;
   }
 
   Element localLookup(String name) => lookupTypeVariable(name);
+}
+
+/**
+ * [TypeDeclarationScope] defines the outer scope of a type declaration in
+ * which the declared type variables and the entities in the enclosing scope are
+ * available but where declared and inherited members are not available. This
+ * scope is used for class declarations during resolution of the class hierarchy
+ * and when resolving typedef signatures. In other cases [ClassScope] is used.
+ */
+class TypeDeclarationScope extends TypeVariablesScope {
+  final GenericElement element;
+
+  @override
+  List<DartType> get typeVariables => element.typeVariables;
+
+  TypeDeclarationScope(Scope parent, this.element) : super(parent);
 
   String toString() => 'TypeDeclarationScope($element)';
 }
 
 abstract class MutableScope extends NestedScope {
   final Map<String, Element> elements;
 
   MutableScope(Scope parent)
       : super(parent),
         this.elements = new Map<String, Element>() {
@@ skipping 66 matching lines @@
 
   Element localLookup(String name) => library.find(name);
   Element lookup(String name) => localLookup(name);
 
   Element add(Element newElement) {
     throw "Cannot add an element to a library scope";
   }
 
   String toString() => 'LibraryScope($library)';
 }