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kotlinlang

hey so, contracts have been around for a while, but the `single()` extension functions dont have htem. I thought that something like

```val myList: List&lt;GeneralType&gt; = ...
val x = myList.single { it is SpecificType }```
would start to smartcast `x` to `SpecificType` instead of `GeneralType` during some upgrade given that we have contracts. But it hasnt. Is there a discussion about this somewhere? I was looking forward to it :(

I don't think contracts are able to express that, currently

```.firstNotNullOf { it as? SpecificType }
```
is close but a little different

i mean `firstIsInstance` is like a combination of `first` and `filterIsInstance`

but i would have thought that a contract would let you say that the condition is true about the return value.... but i guess its an issue of changing the subject? I need to get in to contracts a bit more

<https://youtrack.jetbrains.com/issue/KT-19329/Contracts-to-express-the-effect-of-checks-in-the-filter-lambda-on-the-return-type>