I don't understand interfaces with extension functions. say I have ```class Foo(val s: String) inte...

# getting-started

[y]

I don't understand interfaces with extension functions.
say I have

class Foo(val s: String)

interface MyInterface {
    fun Foo.bar(): String
}

object MyImpl : MyInterface {
    override fun Foo.bar(): String = this.s
}

then given val myImpl = MyImpl and an instance of Foo, how/when can I call `MyImpl`'s implementation of bar()?

[Paul Griffith]

with(MyImpl) {
  someFooInstance.bar()
}

[y]

oh! that's really cool. so the when block brings all the extension functions of MyImpl into scope?

[y]

just wanted to say again that this is really cool

[Paul Griffith]

per https://github.com/Kotlin/KEEP/blob/master/proposals/context-receivers.md#introduction (recommended reading, especially w.r.t the future of multiple receivers in Kotlin)
in this example, MyInterface/MyImpl is the ‘dispatch receiver’ and Foo.bar is the ‘extension receiver’