Suppress some fallout from gen in synstructure

compiler/rustc_macros/src/diagnostics/subdiagnostic.rs

@@ -86,6 +86,9 @@ impl SubdiagnosticDerive {
 
         let diag = &self.diag;
         let f = &self.f;
+
+        // FIXME(edition_2024): Fix the `keyword_idents_2024` lint to not trigger here?
+        #[allow(keyword_idents_2024)]
         let ret = structure.gen_impl(quote! {
             gen impl rustc_errors::Subdiagnostic for @Self {
                 fn add_to_diag_with<__G, __F>(
@@ -100,6 +103,7 @@ impl SubdiagnosticDerive {
                 }
             }
         });
+
         ret
     }
 }