Trait inheritance not supported

[karthikbhargavan]

Code of the following form does not appear to be supported.
At least we see a case where this does not work in libcrux.

trait A {...}
trait B : Copy + Clone+ A {...}

impl A for u8 {...}
impl B for u9 {...}

This kind of pattern gives a KaRaMeL error of the form:

Cannot re-check libcrux_ml_kem.ind_cca.instantiations.portable.unpacked.keypair_from_private_key as valid Low* and will not extract it.  If libcrux_ml_kem.ind_cca.instantiations.portable.unpacked.keypair_from_private_key is not meant to be extracted, consider marking it as Ghost, noextract, or using a bundle. If it is meant to be extracted, use -dast for further debugging.

I can create a more detailed repro later, or maybe there already is one in some other issue

[msprotz]

There is already support for trait inheritance (because it's been used elsewhere), so I would need a repro to look at this. Thanks!