lint level

How seriously the compiler treats a lint: allow, warn, deny, or forbid.

Each lint has a level (allow, expect, warn, deny, forbid) set by attributes, the [lints] table in Cargo.toml, or command-line flags; #[expect] warns if the expected lint does not fire.

Examples

#![deny(clippy::unwrap_used)] makes every .unwrap() a Clippy error.
#[expect(dead_code)] on a function that is in fact called produces the warning this lint expectation is unfulfilled.