syntax_data: {"ast_node_type":"impl","tokens":[{"end":57,"kind":"keyword","start":0,"text":")"}]}
source_snippet:     ) -> impl Iterator<Item: Iterator<Item = Ty<'tcx>>> {
context_before:         tcx: TyCtxt<'tcx>,
context_after:         let layout = tcx.coroutine_layout(def_id, self.args).unwrap();