Underscore for unused parameters in functions

Language Design
1

For lambdas we can use the underscore character for unused parameters which is very nice.

It would be also very nice to use this feature for normal function parameters:

fun(_ : Executor, query : RfidEntryQuery) {  }

Right now, if I try this syntax I get an error about ‘_’ is reserved for Kotlin which makes it possible to add this feature without much headache (I hope).

The use case that results in this is when I pass a function reference with ‘::’

fun attach(on : HTMLElement, callback : (event : Event) -> Unit)) {  }

fun setup() {
    attach(myElement, ::handler)
}

fun handler(event : Event) {
}

If I don’t use the event in handler I get a warning which is actually useful.

However, to remove the warning, I have to add an annotation which has it’s own problems:

  • depending where the programmer puts the suppress may lead to future errors (to wide suppress means possible problems remain hidden)
  • it hurts readability
2

It looks kind of similar to the ticket I posted before: KT-17746.

1 Like
3

Yes, it is basically the same.