taintegral:

With a macro expansion, it looks like this is caused by the use of type alises in trait impls. This impl triggers the lint:

impl<
    __D: ::rkyv::rancor::Fallible + ?Sized,
    T,
    const R: usize,
    const C: usize,
> ::rkyv::Deserialize<Matrix<T, R, C>, __D> for ::rkyv::Archived<Matrix<T, R, C>>

but this one doesn't

impl<
    __D: ::rkyv::rancor::Fallible + ?Sized,
    T,
    const R: usize,
    const C: usize,
> ::rkyv::Deserialize<Matrix<T, R, C>, __D> for ArchivedMatrix<T, R, C>

(note the exchange of ::rkyv::Archived<Matrix<T, R, C>> for ArchivedMatrix<T, R, C>)

I thought we got rid of all of the uses of type alises in trait impls, but I guess I imagined that. If you want to do that change, I'd be happy to review/merge.