Type mismatch when passing functional interface argument

1

If I have this method signature in Java: 

void execute(Handler<AsyncResult<Void>> callback) { ... }

In Kotlin I can just call the function and pass the argument with this code: 

execute { ... }

But, if I create the function with the same signature in Kotlin: 

fun execute(callback: Handler<AsyncResult<Unit>>) { ... }

I can't call the function with same code above, Kotlin won't compile and said this: 

Type mismatch.
Required: Handler<AsyncResult<Unit>> 
Found: () -> Unit ( or to be worse: (???) -> (???) )

Unless if I code like this then it won't be a problem: 

execute( Handler { ... } )

Just fyi, Handler is a functional interface (an interface with @FunctionalInterface annotation).

2

I complained about something similar, see Andrey's answer here:

https://devnet.jetbrains.com/thread/461516

3

Thanks for pointing me to the link.