New lint: `swap_with_temporary` (#14046)

This lint detects inefficient or useless `{std,core}::mem::swap()` calls
such as:

```rust
    // Should be `a = temp();`
    swap(&mut a, &mut temp());
    // Should be `*b = temp();`
    swap(b, &mut temp());
    // Should be `temp1(); temp2();` if we want to keep the side effects
    swap(&mut temp1(), &mut temp2());
```

It also takes care of using a form appropriate for a `()` context if
`swap()` is part of a larger expression (don't ask me why this wouldn't
happen, I have no idea), by suggesting `{ x = y; }` (statement in block)
or `{std,core}::mem::drop((temp1(), temp2())`.

changelog: [`swap_with_temporary`]: new lint

Close #1968

0 files changed, 0 insertions, 0 deletions