Enumerated types
An enumerated type is a nominal, heterogeneous disjoint union type, denoted
by the name of an enum
item. 1
An enum
item declares both the type and a number of variants, each of
which is independently named and has the syntax of a struct, tuple struct or
unit-like struct.
New instances of an enum
can be constructed with a struct expression.
Any enum
value consumes as much memory as the largest variant for its
corresponding enum
type, as well as the size needed to store a discriminant.
Enum types cannot be denoted structurally as types, but must be denoted by
named reference to an enum
item.
1
The enum
type is analogous to a data
constructor declaration in
ML, or a pick ADT in Limbo.