[kristoff_it]

> I don't see why it needs to exist

The symbol namespaces builtins, as those are the only identifiers that aren't declared in the file (either directly or by using `@import`).

[tialaramex]

Although namespacing them keeps them out from under a programmer's feet, which is a significant benefit, it does seem like this would make it harder to find stuff. @cmpxchgStrong, @wasmMemorySize and @embedFile are completely unrelated, but since they're all builtins they're neighbours.

[Conscat]

This is sort of an issue we already deal with in other languages, and imo it's not a huge deal in those. Personally I find @ more reasonable than __builtin_