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```var x = ...``` ```when (x) is X ->``` // can...
# announcements
m
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var x = ...
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when (x) is X ->
// cannot use x as X unless use
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x as X
Is there any other way apart from make
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val x
?
g
Could you show some self contained sample, it’s not clear what you want to do
m
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.
g
I still don’t understand the problem. Smartcast available after any type check or unsafe type cast and not related directly to 
when
m
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
Essentially, I’m asking is there something like 
it
to avoid the recast?
g
this is why I asked about some complete example
it
cannot be used with 
when
it would be backward incompatible change
m
It’s a shame (no pun intended).
g
there is new syntax in 1.3, maybe can help you somehow:
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when (val x = doTypeCheckOrCast()) {
   x // here is val and type safe
}
m
Oh interesting, thanks!
g
I really would like to see some real code snippet, maybe it can be solved in a different way
also smart cast works with 
var
if it’s local variable and cannot be changed by some other part of your code
s
Is 
x
an open property or has custom getter?
g
m
just a local 
var =
g
smart cast works for local 
var
m
Hmmm, doesn’t seem to for me
when(val x = x)
seems to do the trick
but for exactly the same code 
when(x)
does not allow smartcast
s
If would be helpful if you could show us the code in pl.kotl.in
g
maybe you also could share your sample there
This example using 
when
, smartcast also works https://pl.kotl.in/HyqoVpU3X
👍 1
m
Ok I see now. The reason because “is a local variable that is captured by a changing closure”
Presumably from one of the `let`s thats surrounding what needs to be smart casted.
g
what is your use case for 
let
in this example?
Maybe you also could avoid usage of 
var
hard to tell something on this too synthetic code snippet
m
g
still usage of 
let
not clear for me and probably can be avoided
same for 
var
m
For sure the 
Any().let
is just to show the impact of 
let
but you can imagine something useful in there
The 
var
is necessary because it’s reassigned later
g
Yes, in this sample, but probably original code can be rewritten in the way when it is not needed
Sure, this works, because you make x immutable
To be honest I’m not sure why smart cast doesn’t work in this case
because 
let
uses contracts
and have contract to be called exactly once
m
Okay thanks, so in this case what is the best workaround? is it to put 
val x = x
before the 
let
?
g
Imo the best workaround to rewrite code and make x immutable
👍 1
val x = x
also fine
I use this approach a lot
m
Ok. I think in the case of 
when
I quite like 
when(val x = x)
but yes it seems like it should be nearer the 
let
because that is what is causing the issue
s
m
I’m not sure I understand this. How could the code be modified to take advantage of this: https://pl.kotl.in/S1fDdaI2m
s
So I guess we have to wait until KT-7186 got fixed.
g
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
d
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.
👍 2
g
Good to hear 👍
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