Depends on the definition of NodePrefixRef. I don't think there would be any extra allocation if you define it like this:

@martinvonz yeah, probably wrote the doc-comment too fast

As the new commit description explains, I've done all I could to make the change of hash format easier

These are done, thanks for the remarks.

Just a few nits here, but it looks like we're expecting an update on this series anyway, so maybe you can address them.

"deprecate" was a bit too strong. Actually I'd like to downgrade HGWITHRUSTEXT to be something that'll be useful to play with alternative ways of building the Rust extension(s). Example: if someone wants to experiment with PyO3.

My general feeling is that I'd like to deprecate HGWITHRUSTEXT.

@martinvonz in this code, we're in competition with the C implementation, which does something similar.

@durin42 @martinvonz we might have a nice path forward with this, with the suggestion of @kevincox to make Node a truly defined type, not just an alias, with a private member for the bytes.

@kevincox (replying hastily because I'm also finishing something unrelated today).
Doesn't mem::size_of guarantee to take any padding into account? At least that's what the doc seems to say: https://doc.rust-lang.org/std/mem/fn.size_of.html