anchor.diff:          LinkedHashSet.identity();
   
       if (testingExpression is SimpleIdentifier) {
  -      SimpleIdentifier identifier = testingExpression;
  +      SimpleIdentifier identifier = testingExpression as SimpleIdentifier;
         bool sameIdentifier(n) =>
             n is SimpleIdentifier && identifier.staticElement == n.staticElement;
         if (negations.any(sameIdentifier)) {
  -        SimpleIdentifier otherIdentifier = negations.firstWhere(sameIdentifier);
  +        SimpleIdentifier otherIdentifier =
  +            negations.firstWhere(sameIdentifier) as SimpleIdentifier;
           contradictions
               .add(ContradictoryComparisons(otherIdentifier, identifier));
         }
  
positive.code:           return;
          }
  
          final BinaryExpression otherExpression = c;
  
          final String bcLeftOperand = otherExpression.leftOperand.toString();
          final String bcRightOperand = otherExpression.rightOperand.toString();
  
negative.code: 
      if (_contradictions.isEmpty) {
        Set<Expression> set = (binaryExpression != null
            ? _extractComparisons(testingExpression as BinaryExpression)
            : {testingExpression})
          ..addAll(truths)
          ..addAll(negations);
  