{"ast_node_type":"other","tokens":[{"end":68,"kind":"keyword","start":0,"text":"matched_inputs:"}]}
        matched_inputs: &IndexVec<ExpectedIdx, Option<ProvidedIdx>>,
        expected_idx: Option<usize>,
        formal_and_expected_inputs: &IndexVec<ExpectedIdx, (Ty<'tcx>, Ty<'tcx>)>,