rustdoc only writes one file for multiple items exported as _

[CobaltCause]

For example, generating documentation for this code:

mod traits {
    pub trait TraitA {
        fn a();
    }
    pub trait TraitB {
        fn b();
    }
}

pub use traits::{TraitA as _, TraitB as _};

results in two traits named _, which is correct, but, no matter which one you click on, you'll only ever see the a() xor the b() function since rustdoc tries to write the documentation for both traits to the same file. At least, I think that's what's happening.

Meta

rustc --version --verbose:

rustc 1.48.0 (7eac88abb 2020-11-16)
binary: rustc
commit-hash: 7eac88abb2e57e752f3302f02be5f3ce3d7adfb4
commit-date: 2020-11-16
host: x86_64-unknown-linux-gnu
release: 1.48.0
LLVM version: 11.0

[jyn514]

Duplicate of #61592