Is there a way to cause compilation to fail if the deployment target is iOS 12 and the Kotlin native code references a class or method from a later os version? I have tried this with no success, code compiles and the app crashes on launch.

If you are using cocoapods integration - the easiest way will be to specify at your podspec

deployment_target

. In original ruby DSL of cocoapods it looks like this -

spec.ios.deployment_target = '13.0'

. In kotlin dsl it is not documented, as far as I can see - https://kotlinlang.org/docs/native-cocoapods.html#add-and-configure-kotlin-cocoapods-gradle-plugin, but when you take look at sources - https://github.com/JetBrains/kotlin/blob/master/libraries/tools/kotlin-gradle-plug[…]ns/kotlin/gradle/targets/native/cocoapods/CocoapodsExtension.kt - you’ll find

PodspecPlatformSettings

responsible for configuring exactly that.

Unfortunately we aren’t using the Cocoapods integration. We have multiple frameworks and shared deps which results in some bad behaviour when xcode starts building the targets in parallel.