anchor.diff:    }
   
     void registerDynamicFunctionTypeCheck(FunctionType functionType) {
  -    ClassElement classElement = Types.getClassContext(functionType);
  -    if (classElement != null) {
  -      checkedGenericFunctionTypes.putIfAbsent(classElement,
  -          () => new Set<FunctionType>()).add(functionType);
  -    } else {
  -      checkedNonGenericFunctionTypes.add(functionType);
  -    }
  +    // Currently unused.
     }
   
     void emitRuntimeTypeSupport(CodeBuffer buffer, OutputUnit outputUnit) {
  
positive.code: part of dart2js.js_emitter;
  
  class TypeTestEmitter extends CodeEmitterHelper {
    static const int MAX_FUNCTION_TYPE_PREDICATES = 10;
  
    /**
     * Raw ClassElement symbols occuring in is-checks and type assertions.  If the
     * program contains parameterized checks `x is Set<int>` and
  
negative.code:    * typedefs and implicitly through type annotations in checked mode.
     */
    Set<FunctionType> checkedFunctionTypes;
  
    /// Initially contains all classes that need RTI. After
    /// [computeNeededClasses]
  