This code probably shouldn't compile, but it does.

#![feature(splat)]
#![expect(incomplete_features)]

fn main() {
    (|#[splat] x: i32| {
        println!("{x}");
    })(1);
}

cc @teor2345

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Reproducible on the playground with version 1.98.0-nightly (2026-06-29 096694416a4184070914)