# Future<T>.sync constructor

Future<T>.sync(FutureOr<T> computation())

Returns a future containing the result of immediately calling `computation`.

If calling `computation` throws, the returned future is completed with the error.

If calling `computation` returns a `Future<T>`, that future is returned.

If calling `computation` returns a non-future value, a future is returned which has been completed with that value.

## Implementation

    factory Future.sync(FutureOr<T> computation()) {
      try {
        var result = computation();
        if (result is Future<T>) {
          return result;
        } else if (result is Future) {
          // TODO(lrn): Remove this case for Dart 2.0.
          return new _Future<T>.immediate(result);
        } else {
          return new _Future<T>.value(result);
        }
      } catch (error, stackTrace) {
        var future = new _Future<T>();
        AsyncError replacement = Zone.current.errorCallback(error, stackTrace);
        if (replacement != null) {
          future._asyncCompleteError(
              _nonNullError(replacement.error), replacement.stackTrace);
        } else {
          future._asyncCompleteError(error, stackTrace);
        }
        return future;
      }
    }