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avoid-contradictory-expressions

added in: 1.14.0
warning
Pro+
preset: recommended

Warns when several conditions contradict each other.

Contradicting expressions always result in false which is undesired and is usually a sign of a bug or unused code.

Example​

❌ Bad:

void fn() {
  final num = 1;
  final anotherNum = 2;

  // LINT: This expression contradicts one of the previous expressions. Try updating this expression or replacing it with a different expression.
  if (anotherNum == 3 && anotherNum == 4) {}
  
  // LINT: This expression contradicts one of the previous expressions. Try updating this expression or replacing it with a different expression.
  if (anotherNum < 4 && anotherNum > 4) {}
  
  // LINT: This expression contradicts one of the previous expressions. Try updating this expression or replacing it with a different expression.
  if (anotherNum == 2 && anotherNum != 2) {}
  
  // LINT: This expression contradicts one of the previous expressions. Try updating this expression or replacing it with a different expression.
  if (anotherNum == num && anotherNum != num) {}
}

✅ Good:

void fn() {
  final num = 1;
  final anotherNum = 2;

  if (anotherNum == 3 || anotherNum == 4) {} // Correct, different operator
  if (anotherNum < 4 && anotherNum > 2) {} // Correct, 2 instead of 4
  if (anotherNum == 2) {} // Correct, only one comparison
  if (anotherNum == num) {} // Correct, only one comparison
}

Additional Resources​