return false;
    }
    if (out_edge.second != src_oidx_) {
      if (listener->IsInterested()) {
        *listener << "\nexpected output slot to be " << src_oidx_
                  << " but found " << out_edge.second;
      }
      return false;
    }

    return true;
  }

  void DescribeTo(::std::ostream* os) const override {
    if (src_oidx_) {
      *os << "output slot: " << src_oidx_ << ", source: (";

  // CHECK:   [[LIMIT:%.*]] = mhlo.constant dense<4> : tensor<i32>
  // CHECK:   [[CMP:%.*]] = mhlo.compare LT, [[ITER_ARG0]], [[LIMIT]], NOTYPE
  // CHECK:   mhlo.return [[CMP]]
  // CHECK: } do {
  // CHECK:   [[SRC_IDX:%.*]] = "mhlo.dynamic_slice"([[ITER_ARG2]], [[ITER_ARG0]]) <{slice_sizes = dense<1> : tensor<1xi64>}> : (tensor<4xi32>, tensor<i32>) -> tensor<1xi32>