Make isEmpty a getter.

lib/compiler/implementation/world.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.
 
 class World {
   final Compiler compiler;
   final Map<ClassElement, Set<ClassElement>> subtypes;
   final Set<ClassElement> classesNeedingRti;
   final Map<ClassElement, Set<ClassElement>> rtiDependencies;
   final FunctionSet userDefinedGetters;
@@ skipping 22 matching lines @@
 
     compiler.resolverWorld.instantiatedClasses.forEach(addSubtypes);
 
     // Find the classes that need runtime type information. Such
     // classes are:
     // (1) used in a is check with type variables,
     // (2) dependencies of classes in (1),
     // (3) subclasses of (2) and (3).
 
     void potentiallyAddForRti(ClassElement cls, Function callback) {
-      if (cls.typeVariables.isEmpty()) return;
+      if (cls.typeVariables.isEmpty) return;
       if (classesNeedingRti.contains(cls)) return;
       classesNeedingRti.add(cls);
       if (callback != null) {
         callback();
       }
       Set<ClassElement> classes = subtypes[cls];
       if (classes == null) return;
       classes.forEach((ClassElement sub) {
         potentiallyAddForRti(sub, callback);
       });
     }
 
     compiler.resolverWorld.isChecks.forEach((DartType type) {
       if (type is InterfaceType) {
         InterfaceType itf = type;
-        if (!itf.arguments.isEmpty()) {
+        if (!itf.arguments.isEmpty) {
           potentiallyAddForRti(itf.element, null);
         }
       }
     });
 
     List<ClassElement> worklist =
         new List<ClassElement>.from(classesNeedingRti);
-    while (!worklist.isEmpty()) {
+    while (!worklist.isEmpty) {
       Element e = worklist.removeLast();
       Set<Element> dependencies = rtiDependencies[e];
       if (dependencies == null) continue;
       dependencies.forEach((Element other) {
         potentiallyAddForRti(other, () => worklist.add(other));
       });
     }
   }
 
   bool needsRti(ClassElement cls) {
@@ skipping 104 matching lines @@
 class MemberSet {
   final Set<Element> elements;
   final SourceString name;
 
   MemberSet(SourceString this.name) : elements = new Set<Element>();
 
   void add(Element element) {
     elements.add(element);
   }
 
-  bool isEmpty() => elements.isEmpty();
+  bool get isEmpty => elements.isEmpty;
 }