``` fun fromActivity(activity: Activity?): Source ...

# getting-started

[aphex]

fun fromActivity(activity: Activity?): Source = when {
                activity != null && activity is FooActivity -> Source.FOO
                else -> Source.UNKNOWN
            }

Something tells me I don’t need the null check in the above code. Can I get rid of it and have the same exact behavior?

[aphex]

(feel free to respond in a thread so both of our questions don’t collide)

[robin]

Yeah, you can just remove the null check. The is check won't succeed if activity is null.

[robin]

You can even have activity as a parameter to the when expression then.

[aphex]

AWESOME K❤️

[robin]

Actually, if you flip the && expression in your code so that it looks like this:
activity is FooActivity && activity != null
intelliJ will even tell you that the null-check is unnecessary 😉

[aphex]

Hahah yeah, and then it suggests I introduce activity as an argument to when. Fix this lint-check, @jetbrains 😆

[robin]

Why fix it? Works as it should 😄

[robin]

If you mean that it doesn't catch your original situation, that's intended - there are legit cases where you actually want both checks, for example if the second check is much more expensive and you want to short-circuit it if the first check already passes, even if it was technically covered by the second one.