unnecessary_null_checks

Unnecessary use of a null check ('!').

The analyzer produces this diagnostic when a null check operator (!) is used in a context where a nullable value is acceptable.

The following code produces this diagnostic because a null check is being used even though null is a valid value to return:

int? f(int? i) {
  return i!;
}

Remove the null check operator:

int? f(int? i) {
  return i;
}