Relation between externref and anyref about reference-types

[binji]

It looks like anyref is only used in the "Possible Future Extensions" section. In particular, anyref is defined here:

t <: anyref for all reftypes t

Which means that anyref is a super type of all reference types.

OTOH, externref can only represent host references. From the overview:

allow host references to be represented directly by type externref

[rossberg]

What @binji said. IOW, externref is a different type that will be a subtype of anyref once the latter is introduced.

[Horcrux7]

This means I must change anyref to externref now and later I change it back because I need a type for JS and GC objects. Sounds very chaotic.

I expect then that exnref can not be saved in an externref.

[rossberg]

Not everybody is happy with this outcome, but the CG couldn't agree on anything else.

FYI, some folks have argued that exnref should not even be a subtype of anyref. If this is relevant to you, you may want to speak up and describe your use case, e.g. on the EH proposal.

[Horcrux7]

Not everybody is happy with this outcome, but the CG couldn't agree on anything else.

I know there was an endless discussion. I have read it partly because the information content was very small.

If this is relevant to you, you may want to speak up and describe your use case, e.g. on the EH proposal.

No strong requirement. It is always possible to use boxing to convert any object into a GC type. Can be that some things will be simpler. It required only a new thinking. That requires understanding the new structure of WASM.

[rossberg]

I believe this has been answered.