division in where clause leads to incorrect formatting

[lcnr]

rustfmt incorrectly formats the following code:

pub struct Arr
    where [u8;  {10 / 2}]: Send
{}

as

pub struct Arr
where
    [u8; { 10 / 2 }]: Send, {
    10 / 2}]: Send
{}

Both the braces and the division are required.
This bug does not happen for where bounds on traits.

pub trait Arr
    where [u8;  {10 / 2}]: Send
{}
// This is formatted correctly

Found while looking at rust-lang/rust#72819