rustdoc drops impl Foreign<Local> for Foreign

[guswynn]

I tried this code:

use std::convert::AsRef;
pub struct Gus;

impl AsRef<str> for Gus {
    fn as_ref(&self) -> &str {
        todo!()
    }
}

impl AsRef<Gus> for str {
    fn as_ref(&self) -> &Gus {
        todo!()
    }
}

with cargo doc I get:

with cargo +nightly I get:

Meta

stable: rustc 1.50.0 (cb75ad5db 2021-02-10)
nightly: rustc 1.52.0-nightly (d1206f950 2021-02-15) but this also affects whatever nightly docs.rs is on (https://docs.rs/camino/1.0.0/camino/struct.Utf8Path.html#impl-AsRef%3Cstr%3E is missing the for str impl

(separately, I hit rust-lang/cargo#6783 when testing this, where cargo +stable doc --open still used the nightly generated code)

[guswynn]

this also appears to affect beta:

[jyn514]

nightly: rustc 1.52.0-nightly (d1206f9 2021-02-15) but this also affects whatever nightly docs.rs is on (https://docs.rs/camino/1.0.0/camino/struct.Utf8Path.html#impl-AsRef%3Cstr%3E is missing the for str impl

That's rustc 1.52.0-nightly (a15f484b9 2021-02-22), so your nightly is actually earlier.

[apiraino]

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

@rustbot label -I-prioritize +P-high

[GuillaumeGomez]

The commit responsible is this one: 937f629 from #80653

EDIT: For future reference: I was able to find it using cargo-bisect on a "foo" project I created (cargo new foo --lib), containing the file provided in the first comment as lib.rs.

Then I created a test.sh file containing:

#!/bin/sh
rm -rf target-bisect*; cargo doc;grep '"impl-AsRef%3CGus%3E' ` find . -name struct.Gus.html`

Then you just need to run (in your "foo" folder):

$ cargo bisect-rustc --script=./test.sh --test-dir=`pwd`

[GuillaumeGomez]

Actually, I'm wondering about something: why should we see impl AsRef<Gus> for str on the Gus page? It's not implemented on Gus after all... (original issue remains though!)

[guswynn]

@GuillaumeGomez because it's both 1. An api that the crate creates (the way I found this was I saw a str.as_ref call in some code I was reading in the camino crate imma fn that returned a &Utf8Path, that public api was not exposed on doc.rs) and 2. Can't be on the docs for the foreign type (as this impl is in the local crate)

This is definitely a really specific case of coherence, but it would be a downgrade to lose this in docs

[pnkfelix]

Discussed in T-compiler triage meeting. We're going to revert PR #80653 as a way to fix this in the short-term, while the kinks get worked out in the appropriate fix to get this all working (with #80653) again.

[pietroalbini]

A revert for this was backported in both stable 1.52.0 and beta 1.53.0, so it only affects nightly 1.54.0 now. Updating the labels accordingly.

[jyn514]

it only affects nightly 1.54.0 now

The revert should also have been applied to nightly - is #84867 only landing on 1.53? It should land on 1.54 too if so.

[pietroalbini]

@jyn514 well that PR didn't land on 1.54 yet :)

[pietroalbini]

This has been fixed by #84867 on 1.54 too.