How does default parameters in interfaces work? The IDE complains if you try to implement the interface function with the default parameter but it doesn’t seem to mind if you leave it out

would you mind sharing a minimal snippet demonstrating the behavior you’re seeing?

It's because by defining default params you violate abstraction which interfaces provide. For example:

interface Interface {
    fun someFun(p: Int)
}

class Impl: Interface {
    override fun someFun(p: Int = 1) {
        ...
    }
}

val i: Interface = Impl()
i.someFun()

You expect that in the last statement

someFun

will be invoked with default parameter value (that is,

1

), but

i

is of type

Interface

and thus its function needs to be supplied with some value, because compiler uses definition from

Interface

, not

Impl

.

@Shawn https://gist.github.com/luke-c/20bfdd2d9b04e3106ffb38fc722bc927

Yeah, the compiler doesn't allow any default values when overriding a function – even when you attempt to override with the same value.

It works as I would expect to be fair, the default value still works, it’s just a bit confusing when you look at the method signatures