rustdoc emits confusing error for link to enum struct field

[joshlf]

Given the following code with a broken intra-doc link (note the bas instead of baz):

pub enum Foo {
    Bar {
        /// A baz.
        baz: u8,
        /// Just like [`baz`].
        ///
        /// [`baz`]: crate::Foo::Bar::bas
        blah: u8,
    }
}

I would expect cargo doc to emit an error along the lines of:

warning: unresolved link to `self::Foo::Bar::bas`
 --> src/lib.rs:7:22
  |
7 |         /// [`baz`]: crate::Foo::Bar::bas
  |                      ^^^^^^^^^^^^^^^^^^^^ the enum variant `Foo::Bar` has no field named `bas`
  |
  = note: `#[warn(rustdoc::broken_intra_doc_links)]` on by default

Instead, cargo doc emits this error:

warning: unresolved link to `self::Foo::Bar::bas`
 --> src/lib.rs:7:22
  |
7 |         /// [`baz`]: crate::Foo::Bar::bas
  |                      ^^^^^^^^^^^^^^^^^^^^ the enum `Foo` has no variant or associated item named `bas`
  |
  = note: `#[warn(rustdoc::broken_intra_doc_links)]` on by default

When I first encountered this in real code, I thought that the confusing error message was a symptom of the fact that doc comments on enum variant struct fields were not supported, so I almost gave up before realizing that it was just a confusingly-worded error message.

Meta

$ rustdoc --version
rustdoc 1.54.0-nightly (ca82264ec 2021-05-09)

[jyn514]

I think the fix for this is as simple as changing

rust/src/librustdoc/passes/collect_intra_doc_links.rs

Line 355 in d854c3c

unresolved: variant_field_str.into(),

to also include variant_str.

[TaKO8Ki]

@rustbot claim