`items_after_test_module` lints on `#[cfg(test)]` modules that don't have tests in them

Summary

This might be niche, but I have a crate that implements proptest::Arbitrary only when cfg(test). It does so in an inline module, but that inline module is not actually a test module - it's just cfg'd on test. Maybe it could only trigger if there are #[test] items inside? Though maybe expanding macros that might be test functions would conflict with detecting cfg(test). (also, separate, but it seems to be sorta spurious - this triggers it, but this doesn't)

Lint Name

items_after_test_module

Reproducer

I tried this code (sorry, pseudocode cause I'm not sure what causes it and what doesn't - occurs in the code in the link above in rust 1.76):

#[cfg_attr(test, derive(Arbitrary))]
struct Foo {
    #[cfg_attr(test, proptest(strategy = "arbitrary::fancy_strategy()"))]
    foo: u32,
}

#[cfg(test)]
mod arbitrary {
    use super::*;
    pub(super) fn fancy_strategy() -> impl Strategy<Value = u32> {
        ...
    }
}

// more items...

I saw this happen:

items_after_test_module

I expected to see this happen:

nothing

Version

rustc 1.76.0 (07dca489a 2024-02-04)
binary: rustc
commit-hash: 07dca489ac2d933c78d3c5158e3f43beefeb02ce
commit-date: 2024-02-04
host: x86_64-unknown-linux-gnu
release: 1.76.0
LLVM version: 17.0.6

Additional Labels

No response

Start by locating the implementation and tests for the items_after_test_module lint, then reproduce the report with the supplied #[cfg(test)] module containing only a helper function. Compare it with the linked SpacetimeDB examples and verify that modules without test items no longer trigger the lint while genuine test modules still do.