syntax_data: {"ast_node_type":"variable","tokens":[{"end":89,"kind":"keyword","start":0,"text":"let"}]}
source_snippet:             let sig = tcx.instantiate_bound_regions_with_erased(args.as_closure().sig());
context_before:         ty::Closure(def_id, args) => {
context_after:             let env_ty = tcx.closure_env_ty(