custom inner attributes remove source view for module

Code

When a procedural macro is used as an inner attribute (via #![feature(custom_inner_attributes)]), rustdoc omits that module's source file from the HTML source browser view. When clicking the source view of that module, it jumps to the mod module; declaration. The json output also reports the wrong definition span (the one for the mod module;).

Here's a minimal reproducer:

• In macros/src/lib.rs:

  // In macros/src/lib.rs
  #[proc_macro_attribute]
  pub fn identity(_args: TokenStream, input: TokenStream) -> TokenStream {
      input
  }
  

• In src/lib.rs (of course with macros.path = "./macros" in [dependencies]):

  #![feature(custom_inner_attributes, proc_macro_hygiene)]
  pub mod demo;
  

• In src/demo.rs:

  #![macros::identity]
  
  //! This is the demo module!
  

Expected Outcome

• When clicking on the source button inside the docs of the reproducer::demo module, I expected to be brought to the file view of src/demo.rs, but it instead shows src/lib.rs.
• The source view sidebar does not contain src/demo.rs at all.
• The json output reports that the span of reproducer::demo is inside of src/lib.rs

When the inner attribute macro is removed, all of these behave correctly again.

Actual Output

{
  "0": {
    "id": 0,
    "crate_id": 0,
    "name": "demo",
    "span": {
      "filename": "src/lib.rs",
      "begin": [
        2,
        1
      ],
      "end": [
        2,
        14
      ]
    },
    "visibility": "public",
    "docs": "This is the demo module!",
    "links": {},
    "attrs": [],
    "deprecation": null,
    "inner": {
      "module": {
        "is_crate": false,
        "items": [],
        "is_stripped": false
      }
    }
  },
  "1": {
    "id": 1,
    "crate_id": 0,
    "name": "reproducer",
    "span": {
      "filename": "src/lib.rs",
      "begin": [
        1,
        1
      ],
      "end": [
        2,
        14
      ]
    },
    "visibility": "public",
    "docs": null,
    "links": {},
    "attrs": [
      {
        "other": "#[attr = Feature([custom_inner_attributes#0, proc_macro_hygiene#0])]"
      }
    ],
    "deprecation": null,
    "inner": {
      "module": {
        "is_crate": true,
        "items": [
          0
        ],
        "is_stripped": false
      }
    }
  }
}

Version

rustdoc 1.98.0-nightly (f428d123a 2026-06-19)

@rustbot label +F-custom_inner_attributes

Reproduce the issue with macros/src/lib.rs, src/lib.rs, and src/demo.rs, then inspect rustdoc's generated source view and JSON output for the demo module. Done means src/demo.rs appears in the source sidebar, the source link opens that file, and the JSON span points to it rather than src/lib.rs.