Rustdoc shows broken anonymous lifetimes on re-exported signatures

[dtolnay]

# Cargo.toml

[package]
name = "repro"
version = "0.0.0"
edition = "2021"
publish = false

[dependencies]
foo = { path = "foo" }

// src/lib.rs

pub use foo::repro;

# foo/Cargo.toml

[package]
name = "foo"
version = "0.0.0"
edition = "2021"
publish = false

// foo/src/lib.rs

pub fn repro<F>()
where
    F: Fn(&str),
{
    unimplemented!()
}

The correct behavior is for both crates' docs to render repro as:

However, recent versions of nightly rustdoc render foo::repro as the above, while rendering repro::repro incorrectly as:

I believe this is a bug because that is not valid syntax in Rust.

error[E0637]: `'_` cannot be used here
 --> src/lib.rs:3:12
  |
3 |     F: for<'_> Fn(&str),
  |            ^^ `'_` is a reserved lifetime name

[dtolnay]

Bisect:

$ cat bisect.sh 
#!/bin/bash
cargo doc
not rg "for<" $CARGO_TARGET_DIR/doc

$ cargo-bisect-rustc --start 2022-03-31 --end 2022-06-30 --script ./bisect.sh

bisects to 10f4ce3 in nightly-2022-06-23 (#98279 — @cjgillot @petrochenkov)

[dtolnay]

Example affecting the standard library docs:

• alloc::collections::BTreeMap::retain not affected. https://doc.rust-lang.org/beta/alloc/collections/btree_map/struct.BTreeMap.html#method.retain

  

• std::collections::BTreeMap::retain broken. https://doc.rust-lang.org/beta/std/collections/btree_map/struct.BTreeMap.html#method.retain