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.
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The
enumtype is analogous to adataconstructor declaration in Haskell, or a pick ADT in Limbo. ↩