{"ast_node_type":"variable","tokens":[{"end":58,"kind":"keyword","start":0,"text":"if"}]}
        if let FnRetTy::Ty(ref ret_ty) = sig.decl.output {
        let mut spans: Vec<_> = sig.decl.inputs.iter().map(|p| p.span).collect();
            spans.push(ret_ty.span);