Clarifying behavior of rust-project.json `source.include_dirs`

I have a project structured like...

.
├── generated
│   └── foo.rs
├── rust-project.json
└── src
    └── lib.rs

I want to refer to the module foo from src/lib.rs. I thought I could do that with a rust-project.json that looks like...

{
  "crates": [
    {
      "display_name": "rust_test",
      "root_module": "./src/lib.rs",
      "edition": "2021",
      "is_workspace_member": true,
      "source": {
        "exclude_dirs": [],
        "include_dirs": ["./src", "./generated"]
      },
      "deps": []
    }
  ]
}

But mod foo; in src/lib.rs results in unresolved module, can't find module file: foo.rs, or foo/mod.rs.

I think this happens because the attempt to resolve the path to the module is relative to the original file:
https://github.com/rust-lang/rust-analyzer/blob/2397e7a887252aa995d3790164b34b6c76ed94b4/crates/hir-def/src/nameres/mod_resolution.rs#L92-L95
so only paths in src are considered:
https://github.com/rust-lang/rust-analyzer/blob/2397e7a887252aa995d3790164b34b6c76ed94b4/crates/vfs/src/file_set.rs#L30-L35

Should this work, or am I misunderstanding include_dirs?

Start with the reproduced rust-project.json layout and the mod foo; lookup, then read crates/hir-def/src/nameres/mod_resolution.rs around lines 92–95 and crates/vfs/src/file_set.rs around lines 30–35. Determine whether source.include_dirs is intended to affect module resolution; done means the behavior is clarified and, if needed, the relevant implementation or documentation is updated.