Collect the types used in is-checks in the resolver phase.

lib/compiler/implementation/js_backend/emitter.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.
 
 /**
  * A function element that represents a closure call. The signature is copied
  * from the given element.
  */
 class ClosureInvocationElement extends FunctionElement {
   ClosureInvocationElement(SourceString name,
@@ skipping 433 matching lines @@
         addParameterStubs(member, defineInstanceMember);
       }
     } else if (member.kind !== ElementKind.FIELD) {
       compiler.internalError('unexpected kind: "${member.kind}"',
                              element: member);
     }
     emitExtraAccessors(member, defineInstanceMember);
   }
 
   String generateCheckedSetter(Element member, String fieldName) {
-    Type type = member.computeType(compiler);
+    DartType type = member.computeType(compiler);
     if (type.element.isTypeVariable()
         || type.element == compiler.dynamicClass
         || type.element == compiler.objectClass) {
       // TODO(ngeoffray): Support type checks on type parameters.
       return null;
     } else {
       SourceString helper = compiler.backend.getCheckedModeHelper(type);
       Element helperElement = compiler.findHelper(helper);
       String helperName = compiler.namer.isolateAccess(helperElement);
       String additionalArgument = compiler.namer.operatorIs(type.element);
@@ skipping 150 matching lines @@
     if (!checkedSetters.isEmpty()) {
       buffer.add(',\n');
       buffer.add('${Strings.join(checkedSetters, ",\n")}');
     }
     emitInstanceMembers(classElement, buffer, true);
     buffer.add('\n};\n\n');
   }
 
   void generateTypeTests(ClassElement cls,
                          void generateTypeTest(ClassElement element)) {
-    if (compiler.codegenWorld.isChecks.contains(cls)) {
+    if (compiler.codegenWorld.checkedClasses.contains(cls)) {
       generateTypeTest(cls);
     }
     generateInterfacesIsTests(cls, generateTypeTest, new Set<Element>());
   }
 
   void generateInterfacesIsTests(ClassElement cls,
                                  void generateTypeTest(ClassElement element),
                                  Set<Element> alreadyGenerated) {
     for (DartType interfaceType in cls.interfaces) {
       Element element = interfaceType.element;
       if (!alreadyGenerated.contains(element) &&
-          compiler.codegenWorld.isChecks.contains(element)) {
+          compiler.codegenWorld.checkedClasses.contains(element)) {
         alreadyGenerated.add(element);
         generateTypeTest(element);
       }
       generateInterfacesIsTests(element, generateTypeTest, alreadyGenerated);
     }
   }
 
   void emitClasses(CodeBuffer buffer) {
     Set<ClassElement> instantiatedClasses =
         compiler.codegenWorld.instantiatedClasses;
@@ skipping 567 matching lines @@
         sourceName = token.slowToString();
       }
       int totalOffset = bufferOffset + offset;
       sourceMapBuilder.addMapping(
           sourceFile, token.charOffset, sourceName, totalOffset);
     });
   }
 }
 
 typedef void DefineMemberFunction(String invocationName, CodeBuffer definition);