struct EnumTraits

Compile-time metadata about an enum type.

The primary template is undefined. Specializations are generated

automatically for enums registered with `PW_ENUM`.

Specializations provide the following members. Enumerators that share a

value (aliases) are treated as a single *distinct value*.

- `enum_type` --- the enum type itself.

- `underlying_type` --- `std::underlying_type_t

<enum

_type>`.

- `kName` --- unqualified enum name, e.g. `"MyEnum"`.

- `kFullyQualifiedName` --- fully qualified enum name, e.g.

`"::my::ns::MyEnum"`.

- `kTokenDomain` --- the `pw_tokenizer` domain the enum is tokenized in.

- `kDistinctValueCount` --- number of distinct values; equals

`kValues.size()`.

- `kIsContiguous` --- whether the distinct values cover every integer from

`kMin` to `kMax` with no gaps.

- `kMin` / `kMax` --- smallest and largest enumerator values.

- `kValues` --- `std::array

<enum

_type, kDistinctValueCount>` of the distinct

values in ascending order.

- `IsValid(value)` --- returns whether an enumerator or integer value is a

valid enumerator; see `pw::IsValidEnum`.

- `ToString(value)` --- returns the string representation of `value`; see

`pw::EnumToString`.