Missing Implementors for Join and Pattern trait in rustdoc

[tesuji]

Missing Implementors for std::slice::Join trait.

Current output:

While rustdoc displays Borrow trait implementors.

Expected:
Display Implementors for Join trait:

rust/library/alloc/src/slice.rs

Lines 635 to 703 in de32266

	#[unstable(feature = "slice_concat_trait", issue = "27747")]
	pub trait Join<Separator> {
	#[unstable(feature = "slice_concat_trait", issue = "27747")]
	/// The resulting type after concatenation
	type Output;
	/// Implementation of [`[T]::join`](../../std/primitive.slice.html#method.join)
	#[unstable(feature = "slice_concat_trait", issue = "27747")]
	fn join(slice: &Self, sep: Separator) -> Self::Output;
	}
	#[unstable(feature = "slice_concat_ext", issue = "27747")]
	impl<T: Clone, V: Borrow<[T]>> Concat<T> for [V] {
	type Output = Vec<T>;
	fn concat(slice: &Self) -> Vec<T> {
	let size = slice.iter().map(|slice| slice.borrow().len()).sum();
	let mut result = Vec::with_capacity(size);
	for v in slice {
	result.extend_from_slice(v.borrow())
	}
	result
	}
	}
	#[unstable(feature = "slice_concat_ext", issue = "27747")]
	impl<T: Clone, V: Borrow<[T]>> Join<&T> for [V] {
	type Output = Vec<T>;
	fn join(slice: &Self, sep: &T) -> Vec<T> {
	let mut iter = slice.iter();
	let first = match iter.next() {
	Some(first) => first,
	None => return vec![],
	};
	let size = slice.iter().map(|v| v.borrow().len()).sum::<usize>() + slice.len() - 1;
	let mut result = Vec::with_capacity(size);
	result.extend_from_slice(first.borrow());
	for v in iter {
	result.push(sep.clone());
	result.extend_from_slice(v.borrow())
	}
	result
	}
	}
	#[unstable(feature = "slice_concat_ext", issue = "27747")]
	impl<T: Clone, V: Borrow<[T]>> Join<&[T]> for [V] {
	type Output = Vec<T>;
	fn join(slice: &Self, sep: &[T]) -> Vec<T> {
	let mut iter = slice.iter();
	let first = match iter.next() {
	Some(first) => first,
	None => return vec![],
	};
	let size =
	slice.iter().map(|v| v.borrow().len()).sum::<usize>() + sep.len() * (slice.len() - 1);
	let mut result = Vec::with_capacity(size);
	result.extend_from_slice(first.borrow());
	for v in iter {
	result.extend_from_slice(sep);
	result.extend_from_slice(v.borrow())
	}
	result
	}
	}

Meta

rustc --version --verbose: 1.47.0-nightly (9b88e0a 2020-08-15)

@rustbot modify labels: T-rustdoc

[tesuji]

This is a regression from stable-to-nightly: https://doc.rust-lang.org/1.45.2/std/slice/trait.Join.html and beta one has Implementors section.

cc @jyn514

[tesuji]

It has made it way to beta. Pattern trait is also affected: https://doc.rust-lang.org/beta/std/str/pattern/trait.Pattern.html#implementors

@rustbot modify labels: I-prioritize

[LeSeulArtichaut]

(Btw I think you can use @rustbot prioritize as a shorthand)

[tesuji]

The Borrow trait still has Implementors section, I am not sure if this bug affect crates in ecosystem.

[tesuji]

So I think this bug shouldn't affect stable traits, just most unstable traits I saw are affected.

[jyn514]

This is more likely to be #73771 than the refactor I think.

[Mark-Simulacrum]

Yeah, I suspect that given #74672 it might make sense to revert anyway, since it doesn't actually accomplish the goal.

Or someone more experienced with rustdoc may be able to suggest/implement a better patch.

[tesuji]

New discovery: So far only trait exported to std affected. For example with Join trait, in alloc it is normal: https://doc.rust-lang.org/nightly/alloc/slice/trait.Join.html

[tesuji]

Oh right, I have MCVE, it needs two dummy crates.

dummy crate "unstabled"

#![crate_name = "unstabled"]
#![feature(staged_api)]
#![unstable(feature = "thisisnotreal", issue = "27747")]

#[unstable(feature = "asdfasdfasdfa", issue = "27747")]
pub struct Foo<T: Sized + Clone> {
    #[unstable(feature = "asdfasdfasdfa", issue = "27747")]
    bytes: [T],
}

#[unstable(feature = "asdfasdfasdfa", issue = "27747")]
pub trait Join {
    #[unstable(feature = "asdfasdfasdfa", issue = "27747")]
    type Output;

    #[unstable(feature = "asdfasdfasdfa", issue = "27747")]
    fn join(slice: &Self) -> Self::Output;
}

#[unstable(feature = "asdfasdfasdfa", issue = "27747")]
impl<T: Sized + Clone> Join for Foo<T> {
    type Output = Vec<T>;

    fn join(slice: &Self) -> Vec<T> {
        unimplemented!()
    }
}

Crate to run cargo doc:

#![feature(asdfasdfasdfa)]

pub use unstabled::Join;

@rustbot modify labels: -E-needs-mcve

[tesuji]

searched nightlies: from nightly-2020-06-04 to nightly-2020-07-17
regressed nightly: nightly-2020-07-17
searched commits: from 7e11379 to 5c9e5df
regressed commit: 5c9e5df

bisected with cargo-bisect-rustc v0.5.2

Host triple: x86_64-unknown-linux-gnu
Reproduce with:

cargo bisect-rustc 2020-06-04 --end 2020-07-17 --script=./test.bash --without-cargo 

[jyn514]

That rollup includes both #73771 and #73566; of the two I think 73771 is the more likely culprit.

[jyn514]

Marking as P-high as discussed by the prioritization WG.