Create a deterministic `FxHashMap` wrapper

[bjorn3]

It should not provide iteration support, but only insert/remove/get/get_mut and convertion to a sorted vec. We should then use it where possible

This could prevent accidentially causing hashmap related non determinism in most cases.

Originally posted by @bjorn3 in #58281 (comment)

[shivan1b]

Hi @bjorn3 !
If this is not taken up by someone already, can I work on this? I'm a first time contributor to Rust and am browsing through the Easy marked issues.

[bjorn3]

I dont think somebody else is working on this, so go for it.

This wrapper should be put in the rustc_data_structures crate.

[shivan1b]

Hi @bjorn3 do you have name in mind for this wrapper? Also, is it OK if I take some time on this or is this an urgent requirement?

[bjorn3]

Hi @bjorn3 do you have name in mind for this wrapper?

Not really.

Also, is it OK if I take some time on this or is this an urgent requirement?

You can probably take some time.

[petrochenkov]

Semi-related, I'd also like to see an "accumulative" FxHashMap wrapper panicking on any attempts to change or remove existing values in the map.

[RalfJung]

I was told once that FxHashMap does not have a seed in its hasher method and hence it actually is deterministic. Was that wrong information, or did things change since then?