rustdoc: Notable traits shows traits for &[u8] even though the return type is &[Attribute]

[camelid]

This is in the rustc docs, but this can probably be reproduced pretty easily elsewhere.

beta (also on nightly)

stable

Note that there is no notable traits dialog:

[apiraino]

Assigning P-medium as discussed as part of the Prioritization Working Group procedure and removing I-prioritize.

@rustbot label -I-prioritize +P-medium

[pietroalbini]

This affected 1.51.0, the regressed behavior is also present on stable. Changing the labels.

[steffahn]

Reduced:

pub struct Attribute;

pub struct Map<'hir> {}
impl<'hir> Map<'hir> {
    pub fn attrs(&self) -> &'hir [Attribute] { &[] }
}

pub struct List<T>(T);

impl<T> std::ops::Deref for List<T> {
    type Target = [T];
    fn deref(&self) -> &[T] {
        &[]
    }
}

reduced example regresses at nightly-2021-01-09, 937f629 / #80653

The original rustc_middle docs regresses at the same nightly.

@rustbot label -E-needs-bisection -E-needs-mcve

[camelid]

Hmm, I wonder if the revert of that PR will fix this bug then. CC #84867. Would be nice to check once that PR is merged.

[camelid]

This issue seems to be fixed now, presumably because of the revert I mentioned above.