suggest replacing let else with ? statement where applicable

[matthiaskrgr]

Sorry, filed via mobil which doesn't know about issue templates. 😅

might be nice if clippy could lint patterns like this: rust-lang/rust#96471

[est31]

I guess the question_mark lint could be extended to handle this case? Also, maybe one needs to watch out to not suggest let-else first (#8437) to then suggest ?, but suggest ? right away. IDK how conflicts like this are handled.

[est31]

Another example where this lint would have been useful: rust-lang/cargo@cf716fc

[est31]

Given the two samples that we have, I think that most of the times the lint would fire is for functions that return Option. If we simplify for Option, that means that checking for the pattern should be pretty easy. For Result it doesn't make that much sense, as the else clause can't access the thing inside Err.

[MarijnS95]

Yes, would love to see the question_mark lint extended to let-else, and also the mention by @est31 to not first suggest manual_let_else on a block of code, followed by question_mark on the refactored code.

We currently have two patterns in our codebase with both Option and Result where the question mark operator could/should be suggested:

    let x = None::<u32>;
    // Suggest ? here
    let Some(x) = x else {
        return None;
    };

    // Suggest .ok()? here
    let Ok(x) = std::fs::read_to_string("foo") else {
        return None;
    };

Thanks!