<!-- Thank you for filing a bug report! 🐛 Please provide a short summary of the bug, along with any information you feel relevant to replicating the bug. --> I tried this code: ```rust fn main() { #[must_use] {} } ``` I expected to see this happen: Warning that it is unused. Instead, this happened: Not warning. ### Meta <!-- If you're using the stable version of the compiler, you should also check if the bug also exists in the beta or nightly versions. --> `rustc --version --verbose`: ``` rustc 1.58.1 (db9d1b20b 2022-01-20) binary: rustc commit-hash: db9d1b20bba1968c1ec1fc49616d4742c1725b4b commit-date: 2022-01-20 host: aarch64-apple-darwin release: 1.58.1 LLVM version: 13.0.0 ``` <!-- TRIAGEBOT_START --> <!-- TRIAGEBOT_ASSIGN_START --> <!-- TRIAGEBOT_ASSIGN_DATA_START$${"user":"PatchMixolydic"}$$TRIAGEBOT_ASSIGN_DATA_END --> <!-- TRIAGEBOT_ASSIGN_END --> <!-- TRIAGEBOT_END -->