{"ast_node_type":"variable","tokens":[{"end":89,"kind":"keyword","start":0,"text":"let"}]}
    let Impl { attrs, generics, self_ty, items, wc } = parse_macro_input!(input as Impl);
    let ExtensionAttr { vis, trait_ } = parse_macro_input!(attr as ExtensionAttr);
    let headers: Vec<_> = items