syntax_data: {"ast_node_type":"variable","tokens":[{"end":49,"kind":"keyword","start":0,"text":"let"}]}
source_snippet:                     let args = args.as_closure();
context_before:                 ty::Closure(_, args) => {
context_after:                     let sig = tcx.liberate_late_bound_regions(def_id.to_def_id(), args.sig());