syntax_data: {"ast_node_type":"variable","tokens":[{"end":93,"kind":"keyword","start":0,"text":"let"}]}
source_snippet:                 let (callee_features, safe_target_features): (&[_], _) = match fn_ty.kind() {
context_before:                 let sig = fn_ty.fn_sig(self.tcx);
context_after:                     ty::FnDef(func_id, ..) => {