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Regression unused_assignments for variable with underscore prefix captured by closure #149889
Description
Code
I tried this code:
fn lock() -> impl Drop {
struct Handle;
impl Drop for Handle {
fn drop(&mut self) {
}
}
Handle
}
fn bar(_f: impl FnMut(bool)) { }
pub fn foo() {
let mut _handle = None;
bar(move |l| {
if l {
_handle = Some(lock());
} else {
_handle = None;
}
})
}I expected to see this happen: no lints
Instead, this happened: a warning unused_assignments for each assign of _handle
Version it worked on
It most recently worked on: 1.91.1
Version with regression
rustc --version --verbose:
rustc 1.92.0 (ded5c06cf 2025-12-08)
binary: rustc
commit-hash: ded5c06cf21d2b93bffd5d884aa6e96934ee4234
commit-date: 2025-12-08
host: x86_64-pc-windows-msvc
release: 1.92.0
LLVM version: 21.1.3
Activity
dalance commentedon Dec 12, 2025
rust-lang/rust-clippy#16223 may be the same cause.
apiraino commentedon Dec 12, 2025
The bisection points to #149072
cc: @chenyukang
But in reality this is another occurrence of the beta regression originated in #142390
cc: @cjgillot
@rustbot label +L-unused_assignments
Rollup merge of rust-lang#150955 - yukang-fix-149889-unused-assign, r…
Rollup merge of rust-lang#150955 - yukang-fix-149889-unused-assign, r…
Unrolled build for #150955