[Pkg-rust-maintainers] Bug#1042386: Please upgrade to or separately provide newer upstream branch v0.10.

[Peter Green]

I've looked into updating lru and discovered the following.

The new version of lru depends on hashbrown 0.13. There are a couple of issues here.

1. hashbrown has quite a few reverse dependencies,
    I have not investigated these yet.
2. hashbrown has moved to ahash 0.8, ahash 0.8 is available in
    unstable, but is not in testing due to autopkgtest failures.
    Jonas, since ahash is one of your packages can you investigate
    and deal with these.

In terms of lru itself, the big change seems to be that they have
dropped support for zero-sized LruCache objects.

lru seems to have three reverse dependencies, rust-concread,
rust-tracing-log and an embedded copy of an old version of concread
in 389-ds-base.

concread doesn't seem to actively use zero-sized LruCache objects,
but it doesn't seem to actively prevent the user from creating them
either. I don't think any users in Debian do create them though.

tracing-log on the other hand does actively use zero-size LruCache
objects. I was still able to create a patch, but the patch ended up
fairly large.

I've filed upstream bugs, lets see what if anything the upstreams
have to say.