Using newly stabilized library features in new compiler but not in old?

help
1

Is there a way to use a newly stabilized library feature when compiling with the latest compiler while still using the old way with older compiler?

I'm running into an issue with std::ptr::fn_addr_eq(a as fn(), b as fn()) (which was stabilized in 1.85) as a replacement for a as fn() == b as fn(). In 1.85 there is also a new clippy lint that recommends the former rather than the latter.

Is there a way to use the new way on compilers with 1.85 or later while still using the old way on previous compilers?

EDIT: I thought I remember reading somewhere about an attribute to address this issue, but I can't recall where or what to search for. Everything I've looked for hasn't been helpful.

2

There is the rustversion crate that you could use to annotate your items and conditionally compile based on the version of the compiler.

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3

In the specific case of fn_addr_eq(), you should just use the old way — or define your own fn_addr_eq() function for specific cases — with an allow for the lint. This is because the purpose of fn_addr_eq() is to document what the code is doing, and a cfg conditional is overall making the code harder to comprehend, not easier.

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4

Maybe you're thinking of #[cfg(accessible(path))]? But this isn't stable yet.

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5

Yes, that is exactly what I was thinking of. Too bad it isn't stabilized yet.