{"ast_node_type":"struct","tokens":[{"end":77,"kind":"keyword","start":0,"text":"struct"}]}
        struct FindAmbiguousParameter<'a, 'tcx>(&'a FnCtxt<'a, 'tcx>, DefId);
    ) -> Option<ty::GenericArg<'tcx>> {
        impl<'tcx> TypeVisitor<TyCtxt<'tcx>> for FindAmbiguousParameter<'_, 'tcx> {