`unnameable_test_items` does not detect tests in inner modules

[kpreid]

Code

fn _outer_function() {
    mod tests {
        #[test]
        fn inner_test() {}
    }
}

Current output

warning: function `inner_test` is never used
 --> src/lib.rs:4:12
  |
4 |         fn inner_test() {}
  |            ^^^^^^^^^^
  |
  = note: `#[warn(dead_code)]` on by default

Desired output

warning: cannot test inner items
 --> src/lib.rs:3:9
  |
3 |         #[test]
  |         ^^^^^^^
  |
  = note: `#[warn(unnameable_test_items)]` on by default
  = note: this warning originates in the attribute macro `test` (in Nightly builds, run with -Z macro-backtrace for more info)

Rationale and extra context

The desired warning is produced if mod tests is removed so that the inner_test() is directly in the function. The warning should be produced in both cases, since both cases are tests that will not be run.

The warning was last changed in #114414.

Rust Version

Stable 1.81.0 and nightly 1.83.0-nightly (2024-10-05 9096f4f)