var x = ...

when (x) is X ->

// cannot use x as X unless use

x as X

Is there any other way apart from make

val x

?

Could you show some self contained sample, it’s not clear what you want to do

If you pass a

val

into

when

, then smartcasting is available. Otherwise it is not and so you have to do

x as X

. It’s not an unreasonably workaround, but just curious if there is a better way.

I still don’t understand the problem. Smartcast available after any type check or unsafe type cast and not related directly to

when

not when the type being checked is a

var

. True that this issue is not specific to

when

but workaround/solution may be specific to

when

this is why I asked about some complete example

It’s a shame (no pun intended).

there is new syntax in 1.3, maybe can help you somehow:

when (val x = doTypeCheckOrCast()) {
   x // here is val and type safe
}

Oh interesting, thanks!

I really would like to see some real code snippet, maybe it can be solved in a different way

Is

x

an open property or has custom getter?

More details about new when syntax: https://kotlinlang.org/docs/reference/whatsnew13.html#capturing-when-subject-in-a-variable

just a local

var =

smart cast works for local

var

Hmmm, doesn’t seem to for me

If would be helpful if you could show us the code in pl.kotl.in

see example https://pl.kotl.in/HJzLNTU2Q

Ok I see now. The reason because “is a local variable that is captured by a changing closure”

what is your use case for

let

in this example?

Better example: https://pl.kotl.in/BkHUDpI3m

still usage of

let

not clear for me and probably can be avoided

For sure the

Any().let

is just to show the impact of

let

but you can imagine something useful in there

Yes, in this sample, but probably original code can be rewritten in the way when it is not needed

Okay thanks, so in this case what is the best workaround? is it to put

val x = x

before the

let

?

Imo the best workaround to rewrite code and make x immutable

Ok. I think in the case of

when

I quite like

when(val x = x)

I’m not sure I understand this. How could the code be modified to take advantage of this: https://pl.kotl.in/S1fDdaI2m

Actually in think KT-7186 should be extended to contracts, because in case of let there is also contract that already used by compiler, but not in this case

Actually in think KT-7186 should be extended to contracts, because in case of let there is also contract that already used by compiler, but not in this case

Yes, we have it on the table. It requires a bit more work than it may appear, though.

Good to hear 👍