Hello, World! Hey I was looking at contracts again (even though they're still experimental), and couldn't find a way to do what I want, so I'm wondering if it's possible. I have a

fun parseDate(dateStr: String?): Date?

and want to express that if

dateStr

is

null

then the result will be

null

- and also the opposite. Possible?

When you say "the opposite", does it mean that "if dateStr is not null then the result will not be null" ? If yes it seems risky since dateStr could be malformed

Yes that's what I mean. Let's ignore the malformed case for now (I think this will be handled by throwing, not by returning

null

)

Something like returnsNotNull() implies dateStr != Null maybe ?

I've tried, but it's still red if I do something like

val d: Date = parseDate(nonNullStr)

Contracts works in opposite way. Contract

returnsNotNull() implies dateStr != Null

means that "if call

parseDate(str)

returned not null than `str != null`" There is no support of contracts that you want but we are considering support this case

Thanks a lot for chiming in. It may be just me but I have the impression that this use-case would be one of the most common ones.