cargo check reports `unused-assignments` in rustc 1.93.0-nightly

[gmryuuko]

rustc 1.93.0-nightly (c871d09d1 2025-11-24)

#[derive(Debug, Error, Diagnostic)]
#[error("An error occurred in X")]
struct X {
    #[label("Here is the problem")]
    range: SourceSpan,
}

warning: value assigned to `range` is never read
 --> src\main.rs:8:5
  |
8 |     range: SourceSpan,
  |     ^^^^^
  |
  = help: maybe it is overwritten before being read?
  = note: `#[warn(unused_assignments)]` (part of `#[warn(unused)]`) on by default

[ErichDonGubler]

This issue is now in Rust 1.93 stable.

[r6915ee]

From my understanding, it doesn't seem to be possible to use the allow macro on the item to avoid this error. The only workaround I've found is using a Cargo configuration to allow the warning, but that will allow the warning for the entire project, which some might not want:

[build]
rustflags = ["-A", "unused_assignments"]