{"ast_node_type":"other","tokens":[{"end":32,"kind":"keyword","start":0,"text":"sig:"}]}
                    sig: FnSig {
                    num_binders: 0, // FIXME lower `for<'a> fn()` correctly
                        abi: fn_.abi.as_ref().map_or(FnAbi::Rust, FnAbi::from_symbol),