Can't use swap or replace as suggested by manual_swap

[mcarton]

On the following:

fn main() {
    let mut foo = [1, 2];
    let temp = foo[0];
    foo[0] = foo[1];
    foo[1] = temp;
}

Clippy suggests std::mem::swap(&mut foo[0], &mut foo[1]);, but this would mutably borrow foo twice. The correct suggestion for slices would be foo.swap(0, 1). For other types, we should check that the suggestion would not mutably borrow something twice somehow.

[mcarton]

Oh wait, actually the full suggestion is: → fixed in #982

let std::mem::swap(&mut foo[0], &mut foo[1]);
^^^

@Manishearth I there a trick with compiletest-rs to check that there is nothing else before/after the suggestion? → fixed in #983

[thomcc]

I have the related issue where clippy wants me to use mem::swap instead of my manual swap. It's a field through a slice, so it's the same kind of problem:

let id = tris[a].id;
tris[a].id = tris[b].id;
tris[b].id = id;