Collect is checks to only emit the ones that are needed.

frog/leg/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 294 matching lines @@
       // Emit the noSuchMethods on the Object prototype now, so that
       // the code in the dynamicMethod can find them. Note that the
       // code in dynamicMethod is invoked before analyzing the full JS
       // script.
       emitNoSuchMethodCalls(buffer);
     }
   }
 
   void generateTypeTests(ClassElement cls,
                          void generateTypeTest(ClassElement element)) {
-    generateTypeTest(cls);
+    if (compiler.universe.isChecks.contains(cls)) {
+      generateTypeTest(cls);
+    }
     generateInterfacesIsTests(cls, generateTypeTest);
   }
 
   void generateInterfacesIsTests(ClassElement cls,
                                  void generateTypeTest(ClassElement element)) {
     for (Type interfaceType in cls.interfaces) {
-      generateTypeTest(interfaceType.element);
-      generateInterfacesIsTests(interfaceType.element, generateTypeTest);
+      Element element = interfaceType.element;
+      if (compiler.universe.isChecks.contains(element)) {
+        generateTypeTest(element);
+      }
+      generateInterfacesIsTests(element, generateTypeTest);
     }
   }
 
   void emitClasses(StringBuffer buffer) {
     Set seenClasses = new Set<ClassElement>();
     for (ClassElement element in compiler.universe.instantiatedClasses) {
       generateClass(element, buffer, seenClasses);
     }
   }
 
@@ skipping 278 matching lines @@
       emitStaticFinalFieldInitializations(buffer);
       nativeEmitter.emitDynamicDispatchMetadata(buffer);
       buffer.add('var ${namer.CURRENT_ISOLATE} = new ${namer.ISOLATE}();\n');
       Element main = compiler.mainApp.find(Compiler.MAIN);
       buffer.add('${namer.isolateAccess(main)}();\n');
       compiler.assembledCode = buffer.toString();
     });
     return compiler.assembledCode;
   }
 }