It's been tried many many times, but as a network service you simply have no way to enforce what messages you are going to receive until you receive them. So y

It's been tried many many times, but as a network service you simply have no way to enforce what messages you are going to receive until you receive them. So you have to type check at runtime. You can build tooling to make it easier to produce conforming software at each end, but you can't guarantee that someone won't just go ahead and write any old thing. So in practice you still perform validation on each message. Put another way: distributed systems turn all type errors into runtime errors. The guarantees of compile-time checking are severely weakened.