rustdoc does not verify feature gates

[Mark-Simulacrum]

This generates documentation with a stable rustdoc today without any warnings.

#![feature(raw)]

use std::raw::TraitObject;

pub fn bar() {}

Interestingly, rustdoc does seem to check that the feature gate is in the crate (i.e., #![feature(raw)] must exist), and will error if a feature gate has been removed (e.g., custom_attribute on nightly).

[Mark-Simulacrum]

cc @GuillaumeGomez @rust-lang/rustdoc

[kinnison]

I'd guess this is related to https://github.com/rust-lang/rust/blob/master/src/librustdoc/core.rs#L318 somehow. I'm not entirely sure what rustdoc relies on which would mandate the locking in of the permission to use unstable features, but perhaps @GuillaumeGomez would know?

[GuillaumeGomez]

Normally, for such things rustdoc relies on rustc internals to do the work. Maybe an option is badly set?

[pnkfelix]

triage: looks like this should be T-rustdoc's call as to what priority to assign here. Leaving unprioritized and nominated, at least for a week.

[GuillaumeGomez]

I made the priority medium: it's not a huge bug but the quicker it's fixed, the better it'll be for everyone.

[ollie27]

#67989 should fix this.

[Mark-Simulacrum]

@ollie27 Thanks! I've also gone ahead and nominated it for beta backport as it's probably good to close the stability hole sooner rather than later; it's a trivial patch.