It would be really nice if we could replace `ArrayView`/`ArrayViewMut` with custom dynamically-sized types. [RFC 2594](https://github.com/rust-lang/rfcs/pull/2594) is a current proposal for custom DSTs. The current version would work for const-dimensionality views but not for dynamic-dimensionality views (`IxDyn`). I've asked about the dynamic dimensionality case and proposed a couple of ideas. @bluss Maybe you have some more ideas?