Use List instead of Link in the type system.

sdk/lib/_internal/compiler/implementation/enqueue.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 dart2js;
 
 typedef ItemCompilationContext ItemCompilationContextCreator();
 
 class EnqueueTask extends CompilerTask {
   final ResolutionEnqueuer resolution;
@@ skipping 19 matching lines @@
         // TODO(ahe): Consider lifting this restriction.
         if (!library.isInternalLibrary) {
           container = library;
           // TODO(ahe): Is this right?  Is this necessary?
           name = library.getLibraryOrScriptName();
         }
       } else if (element.isClass()) {
         ClassElement cls = element;
         cls.ensureResolved(compiler);
         container = cls;
-        for (var link = cls.computeTypeParameters(compiler);
-             !link.isEmpty;
-             link = link.tail) {
-          addMemberByName(link.head.element);
+        for (DartType parameter in cls.computeTypeParameters(compiler)) {
+          addMemberByName(parameter.element);
         }
       }
       allElementsByName[name] = allElementsByName.putIfAbsent(
           name, () => const Link<Element>()).prepend(element);
       if (container != null) {
         container.forEachLocalMember(addMemberByName);
       }
     }
 
     compiler.libraries.values.forEach(addMemberByName);
@@ skipping 708 matching lines @@
     }
     CodegenWorkItem workItem = new CodegenWorkItem(
         element, itemCompilationContextCreator());
     queue.add(workItem);
   }
 
   void _logSpecificSummary(log(message)) {
     log('Compiled ${generatedCode.length} methods.');
   }
 }