src/doc/reference/src/types/enum.md

   1 # Enumerated types
   2
   3 An *enumerated type* is a nominal, heterogeneous disjoint union type, denoted
   4 by the name of an [`enum` item]. [^enumtype]
   5
   6 An [`enum` item] declares both the type and a number of *variants*, each of
   7 which is independently named and has the syntax of a struct, tuple struct or
   8 unit-like struct.
   9
  10 New instances of an `enum` can be constructed with a [struct expression].
  11
  12 Any `enum` value consumes as much memory as the largest variant for its
  13 corresponding `enum` type, as well as the size needed to store a discriminant.
  14
  15 Enum types cannot be denoted *structurally* as types, but must be denoted by
  16 named reference to an [`enum` item].
  17
  18 [^enumtype]: The `enum` type is analogous to a `data` constructor declaration in
  19              ML, or a *pick ADT* in Limbo.
  20
  21 [`enum` item]: ../items/enumerations.md
  22 [struct expression]: ../expressions/struct-expr.md