UNSAFE<T> function

T UNSAFE<T>(@mustBeAnonymous @noFutures T block())

Executes a block of code that is considered UNSAFE, allowing the use of methods like Outcome.unwrap. This function provides no actual safety guarantees; it only serves as a marker for the must_use_unsafe_wrapper / _or_error lint and as a signal to developers that the contained code can throw.

Use it to explicitly acknowledge that you are handling a potentially failing operation outside the Outcome type system.

Two invocation forms

1. Function-call form — the common one. Returns the block's value:

final value = UNSAFE(() => Ok(1).unwrap());

2. Labeled-statement form — zero runtime cost (a label in Dart is purely lexical when nothing breaks out of it). Suitable when you don't need a return value and you're inside a hot path:

UNSAFE: {
  for (final r in results) {
    someSink.add(r.unwrap());
  }
}

Both forms are recognised by the lint rule.

Implementation

// ignore: non_constant_identifier_names
T UNSAFE<T>(@mustBeAnonymous @noFutures T Function() block) {
  assert(
    isSubtype<T, Never>() || !isSubtype<T, Future<Object>>(),
    '$T must never be a Future.',
  );
  return block();
}