An example with

::

(bound callable reference?). Any way to properly import

Companion

so I don't see it in the code?

class Foo(bar: () -> Bar)

class Bar {
    companion object {
        fun newInstance() = Bar()
    }
}
....
Foo(Bar.Companion::newInstance) //<--- works
Foo(Bar::newInstance) //<--- doesn't work

No, as those have different meaning.

Bar::newInstance

is a reference to a function on

Bar

.

probably won't use it but I'm glad I've seen it)