Tracking Issue for Iterator::try_find

[MOZGIII]

Adds try_find to Iterator.

PR: #63177

fn try_find<F, E, R>(&mut self, f: F) -> Result<Option<Self::Item>, E>
where
    F: FnMut(&Self::Item) -> R,
    R: Try<Ok = bool, Error = E>;

Open questions:

• Decide on just-Result, vs potentially supporting Option and other Try types #85115

[MOZGIII]

I'll start test-running it in the field. The next step for this feature would be to allow coupling the resulting Try type with the closure return type. Apparently, GAT would allow a way to implement this.

[mikeyhew]

Is there an easy workaround to use until this is stabilized?

[MOZGIII]

You can use this crate for now: https://github.com/MOZGIII/iter-try-rs

[mikeyhew]

@MOZGIII thanks. I realized I had a .map call after the .find that I was replacing, so I switched to .filter_map(...).transpose()?

[scottmcm]

Wanted to drop a mention of https://rust-lang.github.io/rfcs/3058-try-trait-v2.html#possibilities-for-try_find in here -- figuring out exactly how this should work is probably a blocker for stabilization here (just Result, just things compatible with Result, like Poll<Result<_, _>>, anything in a family of Try types that can accept Option<_> as the Output type...)