anchor.diff:  
     AbstractBool isBooleanOrNull(int value) => isBoolean(excludeNull(value));
   
  -  AbstractBool isBoolean(int value) => isPotentiallyBoolean(value)
  -      ? AbstractBool.trueOrMaybe(!isPotentiallyNullOrOther(value))
  -      : AbstractBool.False;
  +  AbstractBool isBoolean(int value) {
  +    if (!isPotentiallyBoolean(value)) return AbstractBool.False;
  +    if (value & ~boolMask == 0) return AbstractBool.True;
  +    return AbstractBool.Maybe;
  +  }
   
     AbstractBool isDoubleOrNull(int value) => isDouble(excludeNull(value));
   
  
positive.code:   static const int _nullIndex = 2;
    static const int _otherIndex = 3;
  
    const PowersetBitsDomain(this._closedWorld);
  
    CommonElements get commonElements => _closedWorld.commonElements;
  
negative.code:   }
  
    int excludeNull(int value) {
      return value & ~nullMask;
    }
  
    AbstractBool couldBeTypedArray(int value) => isOther(value);
  