Rustdoc "Auto Trait Implementations" is showing private types instead of the relevant generic bounds

Code

pub struct Foo<T>(Bar<T>);

struct Bar<T>(Box<T>);

Or, see a standard library type such as Vec.

Reproduction Steps

1. cargo doc --open
2. Visit the "Auto Traits" section of Foo

OR

1. https://doc.rust-lang.org/nightly/std/vec/struct.Vec.html#synthetic-implementations

Expected Outcome

Auto trait implementations should, as they do on stable, show their bounds in terms of the generics of the type.

impl<T> Send for Foo<T>
where
    T: Send,

impl<T, A> Send for Vec<T, A>
where
    A: Send,
    T: Send,

Actual Output

impl<T> Send for Foo<T>
where
    Bar<T>: Send,

Bar is a private type and should not appear in the documentation.

impl<T, A> Send for Vec<T, A>
where
    RawVec<T, A>: Send,

RawVec is a private type and should not appear in the documentation.

This prevents users from understanding what the actual bounds on the impl are, because Bar and RawVec may have bounds that are not the obvious ones.

Version

rustdoc 1.100.0-nightly (2e2b193f8 2026-09-02)

Does not reproduce on 1.98.0 or 1.99.0-beta.3 (cbae9b4ca 2026-08-28)

Additional Details

@rustbot label regression-from-stable-to-nightly