enums.md

Enums

Enum definition

enum Enum1<A, B>
  case Case1(a: A)
  case Case2(b: B)
  case Case3
end

This defines these classes,

• class Enum1<A, B> : Object
• class Enum1::Case1<A> : Enum1<A, Never>
• class Enum1::Case2<B> : Enum1<Never, B>
• class Enum1::Case3 : Enum1<Never, Never>

these methods

• Enum1::Case1<A>.new(a: A) -> Enum1::Case1<A>
• Enum1::Case1<A>#a -> A
• Enum1::Case2<B>.new(b: B) -> Enum1::Case2<B>
• Enum1::Case2<B>#b -> B

and these constants.

• ::Enum1 : Meta:Enum1
• ::Enum1::Case1 : Meta:Enum1::Case1
• ::Enum1::Case2 : Meta:Enum1::Case2
• ::Enum1::Case3 : Enum1::Case3

Note that enum case with no parameters (Case3 here) is special.

• They have no type parameters.
• Never is used for superclass type arguments.
• The constant ::Enum1::Case3 holds the (only) instance, not the class.

Enum classes

The class Enum1 is called an Enum class. The classes Enum1::Case1, Enum1::Case2, Enum1::Case3, are called Enum case classses.

Enum classes and enum case classes cannot be an explicit superclass.

# error
class A<T> : Enum1<T, T>
end