Void is just another name for the empty set. It's not an empty set, it's the empty set. Since it has no members it indeed cannot be instantiated. As a Rust lib

Void is just another name for the empty set. It's not an empty set, it's the empty set. Since it has no members it indeed cannot be instantiated. As a Rust library: https://docs.rs/void/1.0.2/void/enum.Void.html https://docs.rs/void/1.0.2/void/enum.Void.html Notice how the empty enum is called... Void. In Rust you have "!" (never) too, which cannot be instantiated either but coerces into any other type. > What is the problem with C++/Java/C#/etc? Is-a polymorphism.