anchor.diff:    }
   
     @override
  -  DartType infer<Expression, Statement, Initializer, Type>(
  +  Expression infer<Expression, Statement, Initializer, Type>(
         ShadowTypeInferrer inferrer,
         Factory<Expression, Statement, Initializer, Type> factory,
         DartType typeContext) {
  
positive.code:   IsJudgment(Expression operand, DartType type) : super(operand, type);
  
    @override
    DartType infer<Expression, Statement, Initializer, Type>(
        ShadowTypeInferrer inferrer,
        Factory<Expression, Statement, Initializer, Type> factory,
        DartType typeContext) {
  
negative.code:             valueType, actualTypes[2 * i + 1], value, value.fileOffset);
        }
      }
      inferredType =
          new InterfaceType(mapClass, [inferredKeyType, inferredValueType]);
      inferrer.listener.mapLiteral(
          this, fileOffset, null, null, null, entries, null, inferredType);
      return null;
    }
  }
  
  