UINTERFACE type

# Just decorate the ufuncs to be implemented with BlueprintImplementableEvent
uClass UMyInterface of UInterface:
  ufuncs(BlueprintImplementableEvent):
    proc myFunc()

# And then implement it
uClass UMyUClass of UObject implements UMyInterface
   ufuncs:
     proc myFunc() =
       log "whatever"

Then you can do

let myInterface: UMyInterface = newUObject[UMyClass]()

Notice: implements will generate a converter for you. static checking will be added in the future.