explicit_iter_loop auto-fix produces non-compiling code for returned closure (needs move)

Summary

The clippy::explicit_iter_loop lint’s auto-fix (via cargo clippy --fix) can produce non-compiling code when the loop is inside a closure that is returned from a function.

In my case, Clippy changes for (xy, part) in grid.iter() to for (xy, part) in grid inside a returned closure, which makes the closure borrow grid instead of capturing it by value. The closure escapes the function, so this triggers E0373 (“closure may outlive the current function”).

The fix should either

• add move to the closure, or
• avoid applying explicit_iter_loop when it would cause this lifetime issue.

Reproducer

Code:

pub fn closest_in_room_range(
    grid: &HashMap<RoomXY, RoomPart>,
) -> impl FnMut(RoomName, CostMatrix) -> SingleRoomCostResult + use<'_> {
    |_: RoomName, mut matrix: CostMatrix| -> SingleRoomCostResult {
        for (xy, part) in grid.iter() {
            ...
        }
        SingleRoomCostResult::CostMatrix(matrix)
    }
}

Current output:

pub fn closest_in_room_range(
    grid: &HashMap<RoomXY, RoomPart>,
) -> impl FnMut(RoomName, CostMatrix) -> SingleRoomCostResult + use<'_> {
    |_: RoomName, mut matrix: CostMatrix| -> SingleRoomCostResult {
        for (xy, part) in grid {
            ...
        }
        SingleRoomCostResult::CostMatrix(matrix)
    }
}

Desired output:

pub fn closest_in_room_range(
    grid: &HashMap<RoomXY, RoomPart>,
) -> impl FnMut(RoomName, CostMatrix) -> SingleRoomCostResult + use<'_> {
    move |_: RoomName, mut matrix: CostMatrix| -> SingleRoomCostResult {
        for (xy, part) in grid {
            ...
        }
        SingleRoomCostResult::CostMatrix(matrix)
    }
}

Version

rustc 1.91.1 (ed61e7d7e 2025-11-07)
binary: rustc
commit-hash: ed61e7d7e242494fb7057f2657300d9e77bb4fcb
commit-date: 2025-11-07
host: x86_64-unknown-linux-gnu
release: 1.91.1
LLVM version: 21.1.2

Additional Labels

No response

Start with the explicit_iter_loop lint's auto-fix implementation and use the returned-closure reproducer in the issue to trace how the replacement affects closure capture. Add a regression test for the shown case and verify that the fixed output compiles without the E0373 error.