List.traverseResultA and friends have x @ y on the error branch, this could potentially blow up

Describe the bug The List.traverseResultA function and similar ones have this critical path:

            match state, fR with
            | Ok ys, Ok y -> traverseResultA' (Ok(y :: ys)) f xs
            | Error errs, Error e -> traverseResultA' (Error(errs @ e)) f xs
            | Ok _, Error e
            | Error e, Ok _ -> traverseResultA' (Error e) f xs

Namely: Error(errs @ e).

If you have many errors (in my situation is was importing an Excel file and all cells in a column were bad), the performance is exponential.

To solve this, one way would be a simple fix to just e :: errs the errors and do a List.rev at the end.

[abelbraaksma]

Change looks good, thanks!

[TheAngryByrd]

Ouch, yeah that’s bad. I mentioned the error path needs to be considered as well in https://github.com/demystifyfp/FsToolkit.ErrorHandling/issues/167 when doing a performance pass at it.