regression: hard error on #[test] attribute on non-associated function

[Mark-Simulacrum]

Crater picked up this issue in a number of crates:

• https://crater-reports.s3.amazonaws.com/beta-1.60-1/beta-2022-02-22/gh/zetok.tox/log.txt
• https://crater-reports.s3.amazonaws.com/beta-1.60-1/beta-2022-02-22/gh/yytian.bignum/log.txt

[INFO] [stdout] 
[INFO] [stdout] error: the `#[test]` attribute may only be used on a non-associated function
[INFO] [stdout]    --> src/toxcore/dht_node.rs:947:5
[INFO] [stdout]     |
[INFO] [stdout] 947 |       #[test]
[INFO] [stdout]     |       ^^^^^^^
[INFO] [stdout] 948 | /     quickcheck! {
[INFO] [stdout] 949 | |         fn dht_node_send_nodes(pns: Vec<PackedNode>) -> TestResult {
[INFO] [stdout] 950 | |             if pns.is_empty() { return TestResult::discard() }
[INFO] [stdout] 951 | |
[INFO] [stdout] ...   |
[INFO] [stdout] 984 | |         }
[INFO] [stdout] 985 | |     }
[INFO] [stdout]     | |_____- expected a non-associated function, found an item macro invocation
[INFO] [stdout]     |
[INFO] [stdout]     = note: the `#[test]` macro causes a a function to be run on a test and has no effect on non-functions
[INFO] [stdout] help: replace with conditional compilation to make the item only exist when tests are being run
[INFO] [stdout]     |
[INFO] [stdout] 947 |     #[cfg(test)]
[INFO] [stdout]     |

cc @estebank - #92959 seems like the likely cause

[estebank]

Ah, didn't realize that we changed from a warning to an error in that PR. It wouldn't need to be reverted, but we need to add a check for if let ast::ItemKind::MacCall(_) = item.kind { to create a warn instead of an error.

[Mark-Simulacrum]

Fixed by #94933 on beta and #94624 on nightly, closing.