Andreas Rossberg

@taralx, do you mean that `A` or `A | B` would not be subtypes of `A | B | C`? Wouldn't that defeat the purpose?

That wouldn't compose, though. Imagine you have `A|T`, where `T` is an import, and that is latter instantiated with `B|C`. You'd need to either disallow unions over imports or disallow...

Not having a non-nullable i31ref would be bad. Then we would perhaps save some casts here, but for the price of requiring more checks there. FWIW, I use the positive...

Variants and tags are quite different: * Variants are _closed_ (statically known) and their cases are _syntactic_ (by position/name). * Tags are _open_ (dynamically extensible) and _generative_ (fresh at runtime)....

> In the [post MVP description for variants](https://github.com/WebAssembly/gc/blob/main/proposals/gc/Post-MVP.md#variants) it mentions that the main reason to have a higher level representation is to allow VMs to pick more efficient representations. But...

Does it actually affect interop which operations are lock-free on the other side?

On 19 May 2017 at 13:25, Andrew Scheidecker wrote: > Do we need shared global variables? Shared vs thread-local is only > meaningful for mutable variables, and mutable shared globals...

There is a wealth of options for enriching the type system in a principled manner to avoid casts in certain situations. They all tend to conflict with simplicity, of course....

Implementations would be expected to hash-normalise all structural types, so that down casts shouldn't cost more. The problem with nominal types is that they are much less modular. You need...

We cannot get rid of null altogether, since some languages will need it. It also is present in current Wasm already, in the disguise of uninitialised table entries. And we...