{"ast_node_type":"variable","tokens":[{"end":96,"kind":"keyword","start":0,"text":"let"}]}
                    let expected_sig = ExpectedSig { cause_span: None, sig: sig_tys.with(hdr) };
                hir::ClosureKind::Closure => {
                    (Some(expected_sig), Some(ty::ClosureKind::Fn))