Noexn type

[thibaudmichaud]

#282 included the notion of a noexn type to mirror the other null types of the GC proposal, but this was not added in the spec yet.
Should it be added, and do we already have an opcode for it?

[aheejin]

I think we should add the opcode. Binaryen also needed it to implement EH. I currently encode it as 0xff for a placeholder: https://github.com/WebAssembly/binaryen/blob/feb8f24128c0c3bd53862b2f39acc5116f8ae87e/src/wasm-binary.h#L478

[rossberg]

Right, this is another example of some feature falling into the intersection of two proposals. Since GC has advanced to phase 4 now, it should be added here. (At least in the overview, in the actual spec we'll need to wait until we rebase on the spec including GC.)

[rossberg]

Please see #298.

[aheejin]

Closed by #298.