A utility package containing all the little functions and classes I find myself reusing frequently. This will be expanded, documented and fit for general public use eventually, when I find the time.

Result

Result<T, E> is a Rust-inspired sealed type for computations that either succeed with a value or fail with an error:

Result<int, String> parseCount(String source) {
  final value = int.tryParse(source);
  return value == null
      ? Result.error('Not a number')
      : Result.ok(value);
}

final message = switch (parseCount('42')) {
  Ok(:final value) => 'Parsed $value',
  Err(:final error) => 'Failed: $error',
};

Results support map, andThen, mapError, fold, unwrap, unwrapError, unwrapOrElse, and toNullable. Ok and Err use value equality when their concrete types and payloads are equal.

Iterables of results expose lazy oks and errs views. Their payloads are available through results.oks.values and results.errs.values. results.sequence() collects every successful value or returns the first error.

The unnamed Result constructor was removed in 2.0. Existing Result.ok(...) and Result.error(...) calls remain supported. The old nullable getters and transform methods are deprecated in favor of pattern matching and the new operations.