Line indented again each time rustfmt is run until it's 100 columns wide

The line containing ::uninit() in the following code is repeatedly indented if rustfmt is run on the file repeatedly. This also causes cargo fmt -- --check to fail, even when cargo fmt was just run, unless the line is as long as permissible.

macro_rules! space_uninit {
    ($capacity:expr) => {
        unsafe {
            core::mem::MaybeUninit::<[core::mem::MaybeUninit<core::primitive::u8>; $capacity]>
                ::uninit()
        }
    };
}

rustfmt version:

$ rustfmt -V
rustfmt 1.4.37-stable (09c42c4 2021-10-18)

Start by running rustfmt 1.4.37 on the Rust snippet containing core::mem::MaybeUninit::<...>::uninit() and repeat formatting to reproduce the indentation drift. Trace the formatter behavior for this macro and qualified path, then verify that repeated runs are stable and cargo fmt -- --check passes immediately after formatting.