There is already a distributed programming library on the system called XPC, so people already have experience with it, but you certainly can't program as if every method call might become remote. Mainly the problem is every call can fail, and sometimes retrying is correct and sometimes it isn't, but also the costs of passing a large function parameter become different cross-process and then more different cross-machine.
Note ObjC already had some language features for an older library (DO) like 'inout' parameters, but they were actually removed because XPC instead only uses callbacks.
There is already a distributed programming library on the system called XPC, so people already have experience with it, but you certainly can't program as if every method call might become remote. Mainly the problem is every call can fail, and sometimes retrying is correct and sometimes it isn't, but also the costs of passing a large function parameter become different cross-process and then more different cross-machine.
Note ObjC already had some language features for an older library (DO) like 'inout' parameters, but they were actually removed because XPC instead only uses callbacks.