For when() to be used as an expression, it needs to be "exhaustive", guaranteeing that there is a branch for each possible situation. Frequently, this means you need an else branch.

However, with enum, we know all possible values up front. So, if you have a branch for each enum constant, you will not need an else branch.

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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
enum and Functions enum and when() enum Class enum name and ordinal enum valueOf() enum values()
Capturing Values in when enum and when() when when as an Expression when with Commas when with Expressions for Branches when with Ranges when Without an Expression when Works with Any Type
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