Support intra-doc linking to `()`

[kpreid]

Code

//! [`()`] is the best type ever!

Expected Outcome

A link to the unit type.

Actual Output

Dead link appearing as "[()]".

Version

rustdoc 1.89.0 (2948388 2025-08-04)
rustdoc 1.91.0-nightly (0060d5a 2025-08-04)

Additional Details

The link can be written as [`()`][primitive@unit] but I think this should not be necessary, since () is an unambiguous, non-generic type name.

@rustbot label +A-intra-doc-links

[imladenov51]

Looks like someone already was on this and said there were too many false positives for (). See #80181 for more information.