Macro ocaml_interop::impl_conv_ocaml_variant

macro_rules! impl_conv_ocaml_variant {
    ($rust_typ:ty => $ocaml_typ:ty {
        $($($tag:ident)::+ $(($($slot_name:ident: $slot_typ:ty),+ $(,)?))? $(=> $conv:expr)?),+ $(,)?
    }) => { ... };
    ($both_typ:ty {
        $($t:tt)*
    }) => { ... };
}

Implements conversion between a Rust enum and an OCaml variant.

See the impl_to_ocaml_variant! and impl_from_ocaml_variant! macros for more details.