Component used: Navigation Version used: 2.8.0-beta03 Devices/Android versions reproduced on:

Simply make a class with a nullable primitive like an Int?

@Serializable data class ExampleRoute(val accountMethod: Int?)

and runtime crash:

java.lang.IllegalArgumentException: integer does not allow nullable values
at androidx.navigation.NavArgument.<init>(NavArgument.kt:210)
at androidx.navigation.NavArgument$Builder.build(NavArgument.kt:199)
at androidx.navigation.NavArgumentBuilder.build(NavDestinationBuilder.kt:394)
at androidx.navigation.NamedNavArgumentKt.navArgument(NamedNavArgument.kt:21)
at androidx.navigation.serialization.RouteSerializerKt.generateNavArguments(RouteSerializer.kt:109)
at androidx.navigation.NavDestinationBuilder.<init>(NavDestinationBuilder.kt:94)
at androidx.navigation.compose.ComposeNavigatorDestinationBuilder.<init>(ComposeNavigatorDestinationBuilder.kt:95)

In the IDE, there is no indication this is wrong, and is perfectly valid in Kotlinx serialization. I understand complex types requiring a barrier, but a nullable primitive seems logical in kotlin. A lint warning or error would be also highly helpful to prevent this from potentially crashing at runtime.