Bump rustc version

[Nadrieril]

Some interesting clause-related changes.

Regarding Clause hashing, I think we should either never hash the binder or prevent hashing without a binder; the current middle-ground is error-prone. Consistently ignoring the binder seems fine.

[W95Psp]

Cool, thanks, will review on Monday!
There is a to_predicate that happens in the hashing, which calls Binder::dummy, that checks if there are any unbound variable, and this can cause panics :(
So that's why I think we should always hash with binders, but I agree that the current situation is pretty bad! But that's not directly related to that PR :)

[Nadrieril]

With this PR we no longer call to_predicate before hashing Clauses

[W95Psp]

Ah, I had no time to look at the code, that's great then! That's simplifies things
Might help with #495 then

[Nadrieril]

There are a few other places where we take shortcuts with binders, we'll have to go through these too

[W95Psp]

Thank you! 😀

Seems OK to me, one thing we should settle on is a vocabulary between clauses and predicates: those things now contain exactly the same pieces of information (if I understand correctly)
We should probably map both Predicate and Clause (from rustc) to Clause (from hax), wdyt?

[W95Psp]

Let's merge whenever you want @Nadrieril (do you have permissions to press merge though?)

[Nadrieril]

I don't have permissions to merge, you can go ahead