{"ast_node_type":"variable","tokens":[{"end":85,"kind":"keyword","start":0,"text":"let"}]}
        let output_is_sized_pred = tupled_inputs_and_output.map_bound(|(_, output)| {
        // (FIXME: technically we only need to check this if the type is a fn ptr...)
            ty::TraitRef::new(cx, cx.require_lang_item(TraitSolverLangItem::Sized), [output])