Like enum, a sealed class works well with when(). We know all possible objects and subclasses of the sealed class when we compile the code, so we know whether the when is "exhaustive", even without an else branch.

You can learn more about this in:
Tags:
Abstract Classes Adding Functions to Classes Adding Properties to Classes Chaining to Superclass Functions Checking Inheritance Via is Classes and Instances Constructor Init-Only Parameters Constructors Data Class enum and Functions enum and when() enum Class enum name and ordinal enum valueOf() enum values() Formal Constructor Declaration Hello, World! (In a Class) Inheritance Inheritance and Constructors Inheritance and Functions Inheritance and Overriding Functions Init Block Inner Classes Inner Classes and Outer this Inner Classes and this is and when Manual Casts Nested Classes Nested Classes and Private Access Non-Nested Sealed Classes override is Transitive Overriding Properties Passing this as a Parameter Printing the Class of Numbers Sealed Classes Sealed Classes and when Secondary Constructors Smart Casts The this Pseudo-Property
Non-Nested Sealed Classes Sealed Classes Sealed Classes and when
Run Edit