Macro-Generated Code

When a developer uses a macro from a 3rd-party crate, it generates code that the developer cannot easily change or fix. Macro-generated code will still be linted, but if that code has any issues the developer cannot do anything to fix it beyond adding an #[allow(...)] attribute.

Because of this, all bevy_lint lint passes should skip code generated by an external macro. This can be done with Span::in_external_macro():

#![allow(unused)]
fn main() {
impl<'tcx> LateLintPass<'tcx> for MyLint {
    fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'tcx>) {
        // Do not lint this expression if it was generated by an external macro.
        if expr.span.in_external_macro(cx.tcx.sess.source_map()) {
            return;
        }

        // ...
    }
}
}

For more information, please see Clippy’s docs on macros, the issue about macros, and the PR that first incorporated these checks.