pattern_never_matches_value_type

The matched value type '{0}' can never match the required type '{1}'.

The analyzer produces this diagnostic when the type of the object being matched can't ever be matched by the pattern.

The following code produces this diagnostic because a double is being matched by a pattern that requires an int, which can never succeed:

void f(String? s) {
  if (s case int _) {}
}

If one of the types is wrong, then change one or both of the types so that the pattern can succeed:

void f(String? s) {
  if (s case String _) {}
}

If the types aren't wrong, then remove the pattern match:

void f(double x) {}