{"ast_node_type":"other","tokens":[{"end":95,"kind":"keyword","start":0,"text":"err.subdiagnostic(errors::FnTraitMissingParen"}]}
                        err.subdiagnostic(errors::FnTraitMissingParen { span: fn_trait_span });
                        // fn foo<F>() where F: FnOnce -> () {}
                    } else if let Ok(snippet) = self.psess.source_map().span_to_snippet(ret_ty_span)