anchor.diff:    // TODO(johnniwinther): Make these field final and remove the default values
     // when [IrBuilder] is a property of [IrBuilderVisitor] instead of a mixin.
   
  -  final List<ir.Parameter> _parameters = <ir.Parameter>[];
  -
     IrBuilderDelimitedState state;
   
     /// A map from variable indexes to their values.
  
positive.code: 
    void _createFunctionParameter(Local parameterElement) {
      ir.Parameter parameter = new ir.Parameter(parameterElement);
      _parameters.add(parameter);
      state.functionParameters.add(parameter);
      ClosureLocation location = jsState.boxedVariables[parameterElement];
      if (location != null) {
  
negative.code: 
    void _createFunctionParameter(Local parameterElement) {
      ir.Parameter parameter = new ir.Parameter(parameterElement);
      if (isInMutableVariable(parameterElement)) {
        state.functionParameters.add(getMutableVariable(parameterElement));
      } else {
  