useless_let_if_seq should not emit a warning if multiple assignments happen

[DaanVandenBosch]

I have code that looks like this:

let img_x: u32;
let img_y: u32;
let pattern_x: u32;
let pattern_y: u32;

if forward {
    img_x = start_x + scan_x;
    img_y = start_y + scan_y;
    pattern_x = scan_x;
    pattern_y = scan_y;
} else {
    img_x = start_x - scan_x;
    img_y = start_y - scan_y;
    pattern_x = scan_width - scan_x - 1;
    pattern_y = scan_height - scan_y - 1;
}

Am I right in thinking that this should be ok with clippy or is there actually a more idiomatic way of doing something like this?

If people agree with me, I'll fix the bug.

[jdnewman85]

(New to rust, so I may be wrong.)

I think something like this:

let (img_x, img_y, pattern_x, pattern_y) = if forward {
    start_x + scan_x,
    start_y + scan_y,
    scan_x,
    scan_y
} else {
    start_x - scan_x,
    start_y - scan_y,
    scan_width - scan_x - 1,
    scan_height - scan_y - 1
}

There is a bit less typing, but primarily combining the declaration with initialization reduces the chances of creating a bug later when editing. If many more variables are added, then it'd probably be better to wrap them in something.

[TimNN]

I'm very much in agreement with the original request in this issue. While using a tuple is possible, I think it can be much clearer to assign the variables directly in the if body. Especially since the compiler will ensure that all the variables are initialized exactly once before they are used.

[nk9]

@rustbot label C-bug