If it is part of the language reference it is part of the language.

Usually when language reference books used to be printed, or we used ISO languages, what is there on paper, is the language.

We are only discussing semantics, if it is hardcoded primitives, or made available via the standard library, specially in case of blessed packages like unsafe which aren't fully implemented, rather magical types for the compiler.

Hence why the only thing you will see here is mostly documentation, https://github.com/golang/go/blob/master/src/unsafe/unsafe.g...

Which is nothing new since the 1960's that there are systems languages with some way to mark code unsafe, the C linage of languages are the ones that decided to ignore this approach.

For a while the GOOS=nacl port and the Google App Engine ports of Go disallowed unsafe pointer manipulation too, so there is some precedent. Throughout some of the ecosystem you can see pieces of "nounsafe" build tag support (e.g. in easyjson).

Somehow I don't think Wasm-GC is going to support bare metal syscalls anytime soon. That stuff all has to be rewritten anyway if you want to target WASM.