The whole list of proposals and where they're at is here: https://github.com/WebAssembly/proposals https://github.com/WebAssembly/proposals You can see that "

The whole list of proposals and where they're at is here: https://github.com/WebAssembly/proposals https://github.com/WebAssembly/proposals You can see that "interface types" is at "Phase 1 - Feature Proposal (CG)", so still early days. And there's a link to the proposal here, for people like me who don't know about it: https://github.com/WebAssembly/interface-types https://github.com/WebAssembly/interface-types