On Sat Dec 27, 2025 at 11:45 AM CET, Jesung Yang wrote: > On Sat, Dec 27, 2025 at 1:57 PM Benno Lossin <[email protected]> wrote: >> On Fri Dec 26, 2025 at 10:36 AM CET, Jesung Yang wrote: >> > On Fri, Dec 26, 2025 at 2:40 AM Benno Lossin <[email protected]> wrote: >> >> On Thu Dec 25, 2025 at 9:37 AM CET, Jesung Yang via B4 Relay wrote: >> >> > + fn emit_overflow_assert( >> >> > + enum_ident: &Ident, >> >> > + variants: &[Ident], >> >> > + repr_ty: &syn::Path, >> >> > + input_ty: &ValidTy, >> >> > + ) -> TokenStream { >> >> >> >> I feel like we should track this via traits rather than using a const >> >> assert. That approach will require & generate much less code. >> > >> > Sorry, but could you elaborate? A small example of what you have in >> > mind would help a lot. >> >> Oh yeah sorry, I had something different in mind compared to what I'll >> describe now, but it achieves the same thing without introducing new >> traits: >> >> We have two options: >> 1) We use `<input_ty as TryFrom<repr_ty>>::try_from` instead of writing >> the `fits` function ourself. >> 2) We require `input_ty: From<repr_ty>`. >> >> The first option would still check every variant and should behave the >> same as your current code. >> >> Option 2 allows us to avoid the const altogether, but requires us to >> choose the smallest integer as the representation (and if we want to be >> able to use both `i8` and `u8`, we can't). I missed this before, so >> using option 1 might be the only way to allow conversions of this kind. > > AFAIK, `<input_ty as TryFrom<repr_ty>>::try_from` cannot be called in > const contexts without `#![feature(const_trait_impl, const_convert)]`. > I assume we want to keep this validation at compile-time? If so, we > might need to stick with the custom `fits` check for now. Please let me > know if I misunderstood you.
Oh yeah that doesn't work (yet) :( I'll take another look at the function itself then. Cheers, Benno
