What does

if (current is Set<*> && ...)

even do? Check whether it isn't null?

Correct

Then just do

!= null

, this is just obvustication ☺️.

why not just

!= null

, or better yet,

?.let {}

using

is

gives a smart cast

The null check also does that.

So instead do the following?

filterStates[requested]?.takeIf { it.isNotEmpty() }?.let { additional ->
    filters[property]?.let { current ->
        if (current.isNotEmpty()) {
            filters[property] = current.plus(additional)
        } else {
            filters[property] = additional
        }
    }
}

I'm not a fan of nested `let`s, I'd go with

!= null

.

yea I guess if you're doing

if()

anyway, you can combine the

!=null

in there to make it a little shorter

Don’t forget that the

if

also contains additional conditions. Is the suggestion there to do

value!!.isNotEmpty()

instead of using the smart cast?

Smart casting works within boolean expressions too:

fun foo(x: String?) {
	if(x != null && x.length == 2)
	    println("hey")
}

compiles.