Experimental(level: Level = Level.ERROR)

Signals that the annotated annotation class is a marker of an experimental API. Any declaration annotated with that marker is thus considered an experimental declaration and its call sites should accept the experimental aspect of it either by using UseExperimental, or by being annotated with that marker themselves, effectively causing further propagation of that experimental aspect.

This class is experimental itself and can only be used with the compiler argument -Xuse-experimental=kotlin.Experimental.