If I were writing this language, I'd probably just compile it to Go, although that means Rust extensions would either incur cgo costs or have to be replaced with Go extensions.
It's barely more expensive than a direct function call but, not so you'd notice unless it's in a hot loop. At which point the lack of cross-language inlining is your real problem.
Cgo is cheap these days, don't worry about it.
It's barely more expensive than a direct function call but, not so you'd notice unless it's in a hot loop. At which point the lack of cross-language inlining is your real problem.