Extern and the relationshop with host

[CharlieTap]

The GC spec introduces the notion of ref.host, ref.extern essentially becomes a wrapper around other reference runtime values. Is it expected that ref.host values are always wrapped in ref.extern, for instance if a host function needs push a value to the stack which wasm doesn't support.

If so would the reference type of this value be ref extern? and technically its inner is heap type of any but it doesn't appear you can encode that in the type system 🤔

[tlively]

That sounds right to me. any.convert_extern can convert any extern reference into an any reference, but how that works is up the engine. On some engines any and extern may have the same representation, so the conversion can lower to a no-op. On other engines, the representations may be different, so the engine may need to use a wrapper object that is compatible with the any reference representation. The spec does not control these implementation details.