I just got caught by a footgun where I'd declared a global counter as:

const COUNTER: AtomicUsize = AtomicUsize::new(0);

and incremented it using COUNTER.fetch_add(1, Ordering::SeqCst). It took me a while to realize why I was always getting 0! There are checks for const declarations not having interior mutability to catch these footguns, but they don't apply to atomics.