avoid-unnecessary-nullable-return-type

has auto-fix

pro+

Warns when the return type of a function or a method is declared nullable, but the function or method always return non-nullable value.

Functions with nullable return values usually require additional checks when using such values (for example, a separate code branch for a null result). Removing unnecessary nullability can help reduce the number of checks and simplify the code.

Example

❌ Bad:

const value = '123';

// LINT: Declared return type is unnecessary marked as nullable. Try removing '?'.
String? function() {
  return 'srt';
}

// LINT: Declared return type is unnecessary marked as nullable. Try removing '?'.
String? function1() {
  return value;
}

// LINT: Declared return type is unnecessary marked as nullable. Try removing '?'.
String? function2() {
  return nonNullable();
}

✅ Good:

const value = '123';

String function() { // Correct, the return value is always non-null
  return 'srt';
}

String function1() {
  return value;
}

String function2() {
  return nonNullable();
}

Example​

Example