could anyone explain why smart-cast doesn’t work f...

# announcements

[david-wg2]

could anyone explain why smart-cast doesn’t work for range checks?

if (pin?.length != 36) throw UnauthorizedResponse()
// pin is smart cast here

if (pin?.length !in (8..36)) throw UnauthorizedResponse()
// pin is not smart cast here

[gildor]

Yes, it doesn’t work

[david-wg2]

but shouldn’t it? 🤔

[gildor]

nope

[david-wg2]

it’s smart cast because you know it’s 36 in the first example
in the second example you know it’s in the range 8 to 36

[david-wg2]

which is just as non-nullable

[gildor]

In theory it’s possible to implement in compiler, but it just doesn’t work now

[david-wg2]

that i understand

[gildor]

also in second case compiler should understand range implementation detail which doesn’t look feasible (only by coupling stdlib implementation details to compiler)

[gildor]

also in general such code looks a bit messy for me. Better to make pin non nullable and handle it properly than combine null and range check, but it’s just my opinion

[david-wg2]

that’s what i ended up doing, i was just curious why it didn’t work

[gildor]

it’s just matter of compiler’s complexity imo

[gildor]

so example with 36 may be handled, probably make sense to create an issue.
But I don’t think that it make sense for range (or even possible for generic implementation)

[christophsturm]

it can’t hurt to file a ticket

[Kroppeb]

Can't a contract help here?

[Kroppeb]

private fun Int?.notInRange(range: IntRange): Boolean {
	contract {
		returns(false) implies (this@notInRange != null)
	}
	return this !in range
}

[Kroppeb]

I tried this before but it seems contracts don't work on infix operators?