Update rustc to latest nightly

[Nadrieril]

This updates rustc to the latest nightly. Required to get recent changes in a helper function that we need in charon to compute discriminant layouts.

You'll notice that traits now get a default Self: MetaSized bound. This is the consequence of the in-progress reqork of the Sized trait to add more granularity; see rust-lang/rust#137944.

[Nadrieril]

I'll let you handle the changelog and version upgrade.

[W95Psp]

Thanks, looks great!
I was not aware of this Sized thing, it's quite interesting.

Before merging I think I need to add a quick phases that throw those constraints away.
I hope I can take some time today to do that, but it's not clear.

[W95Psp]

This should be fine now.
Let's see if ML-KEM breaks

[W95Psp]

Uh, we get a [E0391]: cycle detected when optimizing MIR for ... in our Rust engine.
Sounds like a bug of the compiler 🤔
We need to debug that before merging, and I don't have time any longer today.
Let's see on Monday.

[Nadrieril]

Huh weird, you don't use the MIR though do you? Didn't get any issues on the charon side.

[W95Psp]

No, that's even weirder: it has nothing to do with the frontend!
It's just a bug of rustc while compiling our crate hax-rust-engine: compiling in release crash while compiling in debug works fine O_o

[W95Psp]

I'll try to minimize

[Nadrieril]

oh wow, what cursed thing have you done x)

[W95Psp]

Ah, someone got the same bug and minimized: rust-lang/rust#143534.
There's a PR (rust-lang/rust#143551) and it is in the merge queue!

When that PR is merged into rust, we can update the pin of rustc and finally merge that PR.

[Nadrieril]

rust-lang/rust#143551 has been merged, I've moved the nightly pin forward!

[W95Psp]

Thank you so much, let's merge!