Incorrect warning 28 when a guard references a variable defined as an event argument

[GoogleCodeExporter]

Enter the code below. Error 28 is generated saying that Attribute t is not 
defined. However the generated code is fine because there is an event argument.

class Oven1 {
  Integer leftTime = 0;
  ovenstate {
    s1_1 {
      enterTime(int t) [t > 0] / {leftTime = t;} -> s1_2;
    }
    s1_2 {
      enterTime(int t) [t > 0] / {leftTime = t;} -> s1_2;
      start -> s1_3;
    }
    s1_3 {
    }
  }

  void enterTime(Integer t) {
    leftTime = t;
  }
  void start () {
  }
}

Original issue reported on code.google.com by TimothyCLethbridge on 27 Jan 2014 at 2:56