unused_assignment triggered by closure even though value is used #141615
Description
Code
fn main() { let mut a: Option<u32> = None; let mut cl = move || { a = Some(42); a.take().unwrap() }; println!("{}", cl()) }Current output
warning: value captured by `a` is never read --> src/main.rs:4:9 | 4 | a = Some(42); | ^ | = help: did you mean to capture by reference instead? = note: `#[warn(unused_assignments)]` on by defaultDesired output
warning: value assigned to `a` is never read --> src/main.rs:2:13 | 2 | let mut a: Option<u32> = None; | ^ | = help: maybe it is overwritten before being read? = note: `#[warn(unused_assignments)]` on by defaultRationale and extra context
No response
Other cases
If the initial value is used, then the warning goes away, suggesting that it should warn on that instead:
fn main() { let mut a: Option<u32> = None; let mut cl = move || { let _ = a; a = Some(42); a.take().unwrap() }; println!("{}", cl()) }Rust Version
rustc 1.89.0-nightly (d97326eab 2025-05-15) binary: rustc commit-hash: d97326eabfc3b2c33abcb08d6bc117aefa697cb7 commit-date: 2025-05-15 host: x86_64-unknown-linux-gnu release: 1.89.0-nightly LLVM version: 20.1.4Anything else?
No response