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Comment by steveklabnik | Hacker News Reader

Maybe we’re just speaking at odds here. The current design of the language does not allow this. A different design may make it possible, but that’s a completely different question.

I think what you’re saying is “it is possible to do this with the correct design” and what I’m saying is “that design has not been proposed nor accepted and so the answer today is “that’s not possible”.” Does that sound about right?

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Yes, absolutely! (Although note that I'm not the OP.)

Cool. To be clear, I think that it’s maybe not even possible with symbol versioning, because you need more information than that. The compiler has to know “is this function unsafe or not”, for example, not just “does this symbol exist.” I’m not an expert at symbol versioning, so maybe there’s a way to do this I’m not aware of. There’s also other stuff you’d need, too, I believe... but the real point is, you cannot do it today, and that’s really all I’m trying to say. :)

Yep, definitely. In this specific case of a missing unsafe marker you don’t need symbol versioning at all; you need the stdlib to somehow present two signatures for the same function that the compiler can select between according to the Rust version. It’s only for more complicated cases of API breakage (your function took an i32 but you need to extend it to an i64) that symbol versioning becomes necessary.

And great! All I wanted to point out was that, should the need arise, it is technically possible to tie stdlib function signatures to a particular edition.

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