Suggested map_or_else when value partialy moved

[t-webber]

Summary

The clippy::map_or_else lint suggests erroneous code when partially moving the value in one arm and using it in another.

The ownership is dropped before the test for a map_or_else, but only after the test when doing a match.

Lint Name

map_or_else

Reproducer

I tried this code

#![warn(clippy::nursery)]

#[derive(Default, Debug)]
struct A(Option<String>);

fn main() {
    let a = A::default();
    let _ = match a.0 {
        Some(x) => x,
        None => panic!("{a:?} is invalid."),
    };
}

I saw this happen

warning: use Option::map_or_else instead of an if let/else
[...]
help: try: `a.0.map_or_else(|| panic!("{a:?} is invalid."), |x| x)`

If I follow the lint

#[derive(Default, Debug)]
struct A(Option<String>);

fn main() {
    let a = A::default();
    let _ = a.0.map_or_else(|| panic!("{a:?} is invalid."), |x| x);
}

I get a compilation error: borrow of partially moved value: a (this is normal as a is moved when accessing the 0 field).

I expected

I expected the warning not to be triggered in this case

Version

rustc 1.85.0-nightly (7f75bfa1a 2024-12-30)
binary: rustc
commit-hash: 7f75bfa1ad4e9a9d33a179a90603001515e91991
commit-date: 2024-12-30
host: x86_64-unknown-linux-gnu
release: 1.85.0-nightly
LLVM version: 19.1.6

Additional Labels

@rustbot label +I-suggestion-causes-error
@rustbot label +E-medium

[profetia]

@rustbot claim