Once a function is marked with open, it is open for all subclasses, even if an intermediate class (e.g., Intermezzo) does not override that function.

However, a class can mark an inherited open function as final, to prevent its own subclasses from overriding it.

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
Assigning Function Results Chaining to Superclass Functions Default Parameter Values Expression Bodies Expression Bodies and Return Types Functions with Parameters Functions with Return Types Hello, World! (In a Function) Infix Functions Inheritance and Functions Inheritance and Overriding Functions Local Variables Named Parameter Values override is Transitive Spread Operator Spread Operator with Primitive Types Values for Varargs Varargs
Chaining to Superclass Functions Checking Inheritance Via is Inheritance Inheritance and Constructors Inheritance and Functions Inheritance and Overriding Functions is and when Manual Casts override is Transitive Overriding Properties Smart Casts
Run Edit