Why there is no abstract class for client? why expose `$...` methods?

[lesomnus]

Assume a following proto:

service MerchantService {
	rpc Search(MerchantSearchRequest) returns  (MerchantSearchResponse);
}

Current plugin generates following client code:

class MerchantServiceClient extends $grpc.Client {
  MerchantServiceClient($grpc.ClientChannel channel,
      {$grpc.CallOptions? options,
      $core.Iterable<$grpc.ClientInterceptor>? interceptors})
      : super(channel, options: options,
        interceptors: interceptors);

  $grpc.ResponseFuture<$0.MerchantSearchResponse> search($0.MerchantSearchRequest request, {$grpc.CallOptions? options}) {
    return $createUnaryCall(_$search, request, options: options);
  }
}

It defines a search method that is expected to be used by the users, but it also exposes methods from $grpc.Client that are not expected to be used by them.

How about to generate something like:

abstract class MerchantServiceClient {
  $grpc.ResponseFuture<$0.MerchantSearchResponse> search($0.MerchantSearchRequest request, {$grpc.CallOptions? options}) {
    return $createUnaryCall(_$search, request, options: options);
  }
}

class _MerchantServiceClient extends $grpc.Client implements MerchantServiceClient {
  MerchantServiceClient($grpc.ClientChannel channel,
      {$grpc.CallOptions? options,
      $core.Iterable<$grpc.ClientInterceptor>? interceptors})
      : super(channel, options: options,
        interceptors: interceptors);

  $grpc.ResponseFuture<$0.MerchantSearchResponse> search($0.MerchantSearchRequest request, {$grpc.CallOptions? options}) {
    return $createUnaryCall(_$search, request, options: options);
  }
}

MerchantServiceClient createMerchantServiceClient($grpc.ClientChannel channel,
    {$grpc.CallOptions? options,
    $core.Iterable<$grpc.ClientInterceptor>? interceptors}) {
  return MerchantServiceClient(channel,
      options: options, interceptors: interceptors);
}