A modern programming language that makes developers happier.

kotlinlang

The "no warning" behavior is not specific to numeric values. Other impossible casts behave similarly (e.g. `"" as Int`). All you get at the moment is IDEA highlighting `as` yellow and showing a popup "This cast can never succeed". Not sure why.
I don't think we should make `x` hold `0` though. If anything, an exception should be thrown to make it consistent with Kotlin/JVM and Kotlin/Native
IMHO we might have to introduce boxing for numeric types at some point. Otherwise the subtle differences in behaviour might get really painful with multiplatform projects.