Make isEmpty a getter.

lib/compiler/implementation/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.
 
 part of resolution;
 
 abstract class Scope {
   /**
    * Adds [element] to this scope. This operation is only allowed on mutable
    * scopes such as [MethodScope] and [BlockScope].
@@ skipping 44 matching lines @@
       : super(parent) {
     assert(parent != null);
   }
 
   Element add(Element newElement) {
     throw "Cannot add element to TypeDeclarationScope";
   }
 
   Element lookupTypeVariable(SourceString name) {
     Link<DartType> typeVariableLink = element.typeVariables;
-    while (!typeVariableLink.isEmpty()) {
+    while (!typeVariableLink.isEmpty) {
       TypeVariableType typeVariable = typeVariableLink.head;
       if (typeVariable.name == name) {
         return typeVariable.element;
       }
       typeVariableLink = typeVariableLink.tail;
     }
     return null;
   }
 
   Element localLookup(SourceString name) => lookupTypeVariable(name);
@@ skipping 78 matching lines @@
 
   Element localLookup(SourceString name) => library.find(name);
   Element lookup(SourceString name) => localLookup(name);
 
   Element add(Element newElement) {
     throw "Cannot add an element to a library scope";
   }
 
   String toString() => 'LibraryScope($library)';
 }