Concept ACK, will wait for rebase. I'd like to take look into actually making use of this changes.

Also if you're rebasing anyway, you could remove 46 from build.rs and the associated feature gates.

I'd like to take look into actually making use of this changes.

Please clarify, does that mean:

1. you'd like me to add changes to this PR using the new MSRV?
2. you'd like to investigate yourself using the new MSRV before deciding if we should merge this?
3. something else?

Damn written language, why don't we speak in 0s and 1s

Rebased on master and removed rust_1_46.

@tcharding if you know what to look for feel free to do it yourself, I kinda felt like I was the only one who had an idea because of my enthusiasm. :) There are already some things tracked in #1060 but I was thinking more about arrays/const generics - we should be able to add AsRef<[u8]> + AsMut<[u8]> + Borrow<[u8]> + BorrowMut<[u8]> bound to Hash::Bytes, also where &[u8]: TryInto<Self::Bytes, Error=core::array::TryFromSliceError>.

But I think I did see some other places that would be less annoying now, don't remember where. Also note that neither hex nor PushSlice can use it since they require specific lengths.

No worries, I don't know what to look for but its a good chance for me to read the release notes of Rust 1.41 -> 1.48 and try to learn. Won't be the last time we bump MSRV. I definitely won't claim to find everything that can be improved.