Marks this operation as completed and takes over the outcome of another
TFuture of the same type.
If this operation was already cancelled, nothing happens. If the other
operation was cancelled, this operation is marked as failed with a
TCancelledException.
Marks this operation as completed and takes over the outcome of another TFuture of the same type.
If this operation was already cancelled, nothing happens. If the other operation was cancelled, this operation is marked as failed with a TCancelledException.