feature() is only allowed on Nightly, it's completely disallowed on stable and beta
even for already-stabilized features. So, we autodetect whether the user is using nightly
and conditionally use feature(). This allows the crates to Just Work on current 1.75 beta
and will also Just Work when 1.75 stable is out.
Keeping feature() is desirable to keep support for:
Espressif's xtensa rustc fork. (they build from the stable branch but enable use of feature(), so latest xtensa rustc still requires feature())
Users of older nightlies
Once xtensa rust 1.75 is out, we can remove this (upstream nightlies that require feature() will be quite old by then, so dropping support for them should be OK).
I decided to not use already-made crates like rustversion to do this because they're quite big and do way more than what we need, so I felt badd adding another dep. The code is inspired from rustversion's build.rs.
feature()is only allowed on Nightly, it's completely disallowed on stable and beta even for already-stabilized features. So, we autodetect whether the user is using nightly and conditionally usefeature(). This allows the crates to Just Work on current 1.75 beta and will also Just Work when 1.75 stable is out.Keeping
feature()is desirable to keep support for:feature(), so latest xtensa rustc still requiresfeature())Once xtensa rust 1.75 is out, we can remove this (upstream nightlies that require
feature()will be quite old by then, so dropping support for them should be OK).I decided to not use already-made crates like
rustversionto do this because they're quite big and do way more than what we need, so I felt badd adding another dep. The code is inspired fromrustversion's build.rs.