version: current
platforms: all

https://github.com/akkadotnet/akka.net/blob/dev/src/core/Akka.Streams/Dsl/BidiFlow.cs#L281

Current signature:
BidiFlow<..., TMat> BidiFlow<..., TMat>.AtopMat(BidiFlow<..., TMat2>, Func<TMat, TMat2, TMat3> combine)

combine's result is TMat3, but it is used as TMat