Implement method into_ok_or_err for Result<T, T>

I think it’d be nice to be able to write something like

val a = res.map { it.joinToString("\n") }.into_ok_or_err()

instead of

val a = when (res) {
    is Ok -> res.unwrap().joinToString("\n") // -> String
    is Err -> res.unwrapError() // -> String
}

This feature already exists in Rust Nightly.

[michaelbull]

Does this differ from merge?

[michaelbull]

No worries, here’s the wiki entry for it if that helps.