rust-clippy/tests/ui/swap.fixed

// run-rustfix

#![warn(clippy::all)]
#![allow(
    clippy::disallowed_names,
    clippy::no_effect,
    clippy::redundant_clone,
    redundant_semicolons,
    dead_code,
    unused_assignments
)]

struct Foo(u32);

#[derive(Clone)]
struct Bar {
    a: u32,
    b: u32,
}

fn field() {
    let mut bar = Bar { a: 1, b: 2 };

    std::mem::swap(&mut bar.a, &mut bar.b);

    let mut baz = vec![bar.clone(), bar.clone()];
    let temp = baz[0].a;
    baz[0].a = baz[1].a;
    baz[1].a = temp;
}

fn array() {
    let mut foo = [1, 2];
    foo.swap(0, 1);

    foo.swap(0, 1);
}

fn slice() {
    let foo = &mut [1, 2];
    foo.swap(0, 1);

    foo.swap(0, 1);
}

fn unswappable_slice() {
    let foo = &mut [vec![1, 2], vec![3, 4]];
    let temp = foo[0][1];
    foo[0][1] = foo[1][0];
    foo[1][0] = temp;

    // swap(foo[0][1], foo[1][0]) would fail
    // this could use split_at_mut and mem::swap, but that is not much simpler.
}

fn vec() {
    let mut foo = vec![1, 2];
    foo.swap(0, 1);

    foo.swap(0, 1);
}

fn xor_swap_locals() {
    // This is an xor-based swap of local variables.
    let mut a = 0;
    let mut b = 1;
    std::mem::swap(&mut a, &mut b)
}

fn xor_field_swap() {
    // This is an xor-based swap of fields in a struct.
    let mut bar = Bar { a: 0, b: 1 };
    std::mem::swap(&mut bar.a, &mut bar.b)
}

fn xor_slice_swap() {
    // This is an xor-based swap of a slice
    let foo = &mut [1, 2];
    foo.swap(0, 1)
}

fn xor_no_swap() {
    // This is a sequence of xor-assignment statements that doesn't result in a swap.
    let mut a = 0;
    let mut b = 1;
    let mut c = 2;
    a ^= b;
    b ^= c;
    a ^= c;
    c ^= a;
}

fn xor_unswappable_slice() {
    let foo = &mut [vec![1, 2], vec![3, 4]];
    foo[0][1] ^= foo[1][0];
    foo[1][0] ^= foo[0][0];
    foo[0][1] ^= foo[1][0];

    // swap(foo[0][1], foo[1][0]) would fail
    // this could use split_at_mut and mem::swap, but that is not much simpler.
}

fn distinct_slice() {
    let foo = &mut [vec![1, 2], vec![3, 4]];
    let bar = &mut [vec![1, 2], vec![3, 4]];
    std::mem::swap(&mut foo[0][1], &mut bar[1][0]);
}

#[rustfmt::skip]
fn main() {

    let mut a = 42;
    let mut b = 1337;

    std::mem::swap(&mut a, &mut b);

    ; std::mem::swap(&mut a, &mut b);

    let mut c = Foo(42);

    std::mem::swap(&mut c.0, &mut a);

    ; std::mem::swap(&mut c.0, &mut a);
}

fn issue_8154() {
    struct S1 {
        x: i32,
        y: i32,
    }
    struct S2(S1);
    struct S3<'a, 'b>(&'a mut &'b mut S1);

    impl std::ops::Deref for S2 {
        type Target = S1;
        fn deref(&self) -> &Self::Target {
            &self.0
        }
    }
    impl std::ops::DerefMut for S2 {
        fn deref_mut(&mut self) -> &mut Self::Target {
            &mut self.0
        }
    }

    // Don't lint. `s.0` is mutably borrowed by `s.x` and `s.y` via the deref impl.
    let mut s = S2(S1 { x: 0, y: 0 });
    let t = s.x;
    s.x = s.y;
    s.y = t;

    // Accessing through a mutable reference is fine
    let mut s = S1 { x: 0, y: 0 };
    let mut s = &mut s;
    let s = S3(&mut s);
    std::mem::swap(&mut s.0.x, &mut s.0.y);
}