unnecessary_map_or suggests code that does not compile

[Kobzol]

Summary

The unnecessary_map_or lint can produce a suggestion that causes the resulting code to not compile. It suggests replacing map_or(false, |v| v == x) with == Some(x), but the problem is that is x isn't Copy, then Some(x) moves x, and it then cannot be used further.

Lint Name

unnecessary_map_or

Reproducer

I tried this code:

fn get_foo() -> Option<String> { None }

fn main() {
    let s = String::from("foo");
    let eq = get_foo().map_or(false, |v| v == s); // Flagged with clippy::unnecessary_map_or
    //let eq = get_foo() == Some(s); // Suggested replacement. Does not compile, because it moves `s`

    println!("{s}");
}

Version

rustc 1.84.1 (e71f9a9a9 2025-01-27)
binary: rustc
commit-hash: e71f9a9a98b0faf423844bf0ba7438f29dc27d58
commit-date: 2025-01-27
host: x86_64-unknown-linux-gnu
release: 1.84.1
LLVM version: 19.1.5

Additional Labels

No response

[y21]

I guess we could still suggest get_foo().as_ref() == Some(&s) for !Copy types? (Or fall back to the more general get_foo().is_some_and(|v| v == s))

[Kobzol]

I used as_ref to solve this issue in the code where the lint was fired. Not sure if it works in all cases, but if the types match, it probably should.

[spirali]

@rustbot claim

[samueltardieu]

@spirali Oops, I didn't see that you claimed it (my browser was open on this page and didn't refresh). If you want I can close my PR and let you do yours.

[spirali]

@samueltardieu No problem, do not close your PR. I can still learn on this and then compare our solutions or I will try to find another entry task.