fix: fix ICE in custom-test-frameworks feature

[Ezrashaw]

Fixes #107454

Simple fix to emit error instead of ICEing. At some point, all the code in tests.rs should be refactored, there is a bit of duplication (this PR's code is repeated five times over lol).

r? @Nilstrieb (active on the linked issue?)

[Noratrieb]

Interesting, with #[test] it compiles but gives a warning (and doesn't run the inner test)

#[test]
fn uwu() {
    #[test]
    fn owo() {}
}

warning: cannot test inner items
 --> a.rs:3:2
  |
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)

running 1 test
test uwu ... ok

The lint also applies to #[test_case], so I think it would be more correct to not emit a hard error here and simple continue as normal, building the result and then letting the lint fire. Here, we have an Annotatable::Stmt with the StmtKind::Item. I guess this should just also be supported. (having it on something that isn't an item like a let statement is also a hard error for #[test].

[Ezrashaw]

@Nilstrieb Updated to match your description. I plan on doing something with custom_test_frameworks soonish but this is a good stopgap to stop an ICE.

[Noratrieb]

👀 sounds cool

[Ezrashaw]

@Nilstrieb CI passing, can we land this?

[Noratrieb]

@bors r+ rollup

[bors]

📌 Commit c05bebc has been approved by Nilstrieb

It is now in the queue for this repository.