syntax_data: {"ast_node_type":"variable","tokens":[{"end":49,"kind":"keyword","start":0,"text":"let"}]}
source_snippet:                 let sig = fn_ty.fn_sig(self.tcx);
context_before:                 let fn_ty = self.thir[fun].ty;
context_after:                 let (callee_features, safe_target_features): (&[_], _) = match fn_ty.kind() {