syntax_data: {"ast_node_type":"variable","tokens":[{"end":29,"kind":"keyword","start":0,"text":"let"}]}
source_snippet:             let mut sig = tcx
context_before:         ty::FnDef(def_id, args) => {
context_after:                 .instantiate_bound_regions_with_erased(tcx.fn_sig(def_id).instantiate(tcx, args));