Compilation warning does not appear even if #[must_use] is used in a non-function.

[Danue1]

I tried this code:

fn main() {
    #[must_use]
    {}
}

I expected to see this happen: Warning that it is unused.

Instead, this happened: Not warning.

Meta

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

[PatchMixolydic]

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