CanBeNonNullable false-negative

[BraisGabin]

Expected Behavior

assignedExpression violates CanBeNonNullable.

private fun visitAssignment(assignedExpression: KtExpression?) {
    if (assignedExpression == null) return
    val name = if (assignedExpression is KtQualifiedExpression) {
        assignedExpression.selectorExpression
    } else {
        assignedExpression
    }?.text ?: return
    assignments.getOrPut(name) { mutableSetOf() }.add(assignedExpression)
}

Observed Behavior

detekt is fine with that code

Context

If a function returns Unit any null check to exit the function if the parameter is null should be consider as a parameter that could be non-null.

I saw this false-negative while working on this PR: #4491

Your Environment

• Version of detekt used: main
• Link to your project (if it's a public repository): detekt.

[cortinico]

Isn't #4431 supposed to catch this actually?

[BraisGabin]

Yes, but it is not.

[VitalyVPinchuk]

Hi!
Can I work on this?

[BraisGabin]

Please go ahead :)

[VitalyVPinchuk]

Should !is in if / when statements also be reported?
e.g.

fun foo(a: Int?) {
    if (a !is Int) return
    println(a)
}

[BraisGabin]

Never though of someone writing something like that. But if it's not too difficult to control that case I don't see why not.

[VitalyVPinchuk]

I'm just looking through the tests for the rule and there are such cases
Yes, I'd rather stick to more common ways of null checking. At least for now.