Mutable slices with ranges

[franziskuskiefer]

Eurydice fails when trying to extract something like fun(&mut buf[0..8]).

See for example this change cryspen/libcrux@a84d517#diff-cac793f2bb8c1229c9c3bbd71a681b9daf1cecd9646ed3e2a5ab208f47c9fc48R38

[msprotz]

Looking at the commit the issue appears to be with [..] specifically, correct?

[franziskuskiefer]

Full range is definitely an issue. But I think I the others, like [0..8] failed as well. But only when mutable. We should do small reproducers for these.

[msprotz]

fn f(x: &mut [u8]) {}

fn main() {
    let x = [0; 1u8];
    f(&mut x[..]);
}

this is a minimal repro (bumped into this again) -- the way to fix it is probably to recognize this as a distinguished pattern and emit a call to array_to_subslice, by written a pattern against the name matching facility of Charon.