False positive in UnnecessaryApply

[BraisGabin]

Expected Behavior

If we use the return value of apply, the UnnecessaryApply rule should never flag that usage.

Observed Behavior

UnnecessaryApply flags some of those.

Steps to Reproduce

val a = listOf(mutableListOf(""))
    .map { it.apply { add("") } }

Context

Reported by zmunm in slack: https://kotlinlang.slack.com/archives/C88E12QH4/p1596599789239000

I really don't like this code because it goes agains immutability. But it's legit code so we should not flag it in this rule.

Your Environment

• Version of detekt used: master, 1.11.0-RC1

[zsmoore]

I'll jump into this one that we are also seeing this when doing a

object = data?.let { data -> new Object().apply { setData(data) } }
swapped to also temporarily to avoid checkstyle error

[BraisGabin]

Yes, I think this is the same case. You are using the return of apply as the return of let. And UnnecessaryApply doesn't check that.

[cortinico]

If we use the return value of apply, the UnnecessaryApply rule should never flag that usage.

Turns out we already have the logic to do this, but only if type resolution is active. I'm restricting UnnecessaryApply to run only when type resolution is active to avoid this false positive here #2963