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Co-authored-by: Oli Scherer <[email protected]>

Author: eholk

compiler/rustc_trait_selection/src/error_reporting/traits/fulfillment_errors.rs

@@ -907,8 +907,8 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
                 .coroutine_kind(self.tcx.coroutine_for_closure(closure_def_id))
                 .unwrap()
             {
-                rustc_hir::CoroutineKind::Desugared(desugaring, _) => format!("{desugaring}"),
-                coro => format!("{coro}"),
+                rustc_hir::CoroutineKind::Desugared(desugaring, _) => desugaring.to_string(),
+                coro => coro.to_string(),
             };
             let mut err = self.dcx().create_err(CoroClosureNotFn {
                 span: self.tcx.def_span(closure_def_id),