syntax_data: {"ast_node_type":"variable","tokens":[{"end":26,"kind":"keyword","start":0,"text":"let"}]}
source_snippet:     let mut vars = vec![];
context_before:     let coroutine_layout = tcx.mir_coroutine_witnesses(def_id);
context_after:     let bound_tys = tcx.mk_type_list_from_iter(