Specify the underlying type of an enumeration only when necessary

Reason

The default is the easiest to read and write. int is the default integer type. int is compatible with C enums.

Example

enum class Direction : char { n, s, e, w,
                              ne, nw, se, sw };  // underlying type saves space

enum class Web_color : int32_t { red   = 0xFF0000,
                                 green = 0x00FF00,
                                 blue  = 0x0000FF };  // underlying type is redundant

Note

Specifying the underlying type is necessary to forward-declare an enum or enum class:

enum Flags : char;

void f(Flags);

// ....

enum Flags : char { /* ... */ };

or to ensure that values of that type have a specified bit-precision:

enum Bitboard : uint64_t { /* ... */ };

Enforcement

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