```fun dummy(input: List<Any>): Stream<So...

# announcements

[Czar]

fun dummy(input: List<Any>): Stream<SomeSpecificType> =
		input.parallelStream().map {
			when {
				it is String -> SomeSpecificType(it)
				else -> performActionWhichReturnsBoolean(it)
			}
		}.filter { it is SomeSpecificType }

This is colored red and shows following error:

Type mismatch.
Required: Stream<SomeSpecificType>
Found: Stream<Serializable!>!

Is this a known issue? I googled around but couldn't find it.
This is not my real code of course, just something syntactically identical.