The following may be used in an expression wherever an int or unsigned int may
be used:
— An object or expression with an integer type whose integer conversion rank is less
than the rank of int and unsigned int.
— A bit-field of type _Bool, int, signed int, or unsigned int.
If an int can represent all values of the original type, the value is converted to an int;
otherwise, it is converted to an unsigned int. These are called the integer
promotions.48) All other types are unchanged by the integer promotions.