Given a `reified R` I would like to return a defau...

# announcements

[hudsonb]

Given a reified R I would like to return a default comparator to use based on `R`s type. Is there any way to do something like this?

inline fun <reified R> defaultComparator(): Comparator<R>? = when {
    R::class.isSubclassOf(Comparable::class) -> naturalOrder<R>()  // Error: Type arg not within bounds
    // ... others
    else -> null
}

[diesieben07]

You'll have to do an unchecked cast here

[hudsonb]

naturalOrder expects a Comparable<R> but AFAIK there's no way to indicate that R is Comparable<R>?

[diesieben07]

naturalOrder<Nothing>() as Comparator<R>

[hudsonb]

Thanks! Never would have thought to try that

[diesieben07]

Nothing is a great tool if you're trying to fight the type system 😄

[Katya Yurukova]

Or you could bound R to Comparable<R> if you want to operate only on comparable types

[hudsonb]

Can't do that unfortunately, it's possible R is not Comparable<R>.