For the purposes of [conv.prom],
a *converted bit-field* is a prvalue that is the result of
an lvalue-to-rvalue conversion ([conv.lval]) applied to
a bit-field ([class.bit]).

A prvalue that is not a converted bit-field and has an integer type other than
bool, char8_t, char16_t,
char32_t, or wchar_t whose integer conversion
rank ([conv.rank]) is less than the rank of int can be
converted to a prvalue of type int if int can represent
all the values of the source type; otherwise, the source prvalue can be
converted to a prvalue of type unsigned int.

A prvalue of an unscoped enumeration type whose underlying type is not
fixed can be converted to a prvalue of the first of the following
types that can represent all the values of the enumeration ([dcl.enum]): int,
unsigned int, long int, unsigned long int,
long long int, or unsigned long long int.

If none of the types in that
list can represent all the values of the enumeration, a prvalue of an unscoped
enumeration type can be converted to a prvalue of the extended integer type with lowest
integer conversion rank ([conv.rank]) greater than the rank of long long
in which all the values of the enumeration can be represented.

If there are
two such extended types, the signed one is chosen.

A prvalue of an unscoped enumeration type whose underlying type is
fixed ([dcl.enum]) can be converted to a prvalue of its underlying type.

Moreover,
if integral promotion can be applied to its underlying type, a prvalue of an unscoped
enumeration type whose underlying type is fixed can also be converted to a prvalue of
the promoted underlying type.

A converted bit-field of integral type can be converted
to a prvalue of type int if int can represent all the
values of the bit-field; otherwise, it can be converted to
unsigned int if unsigned int can represent all the
values of the bit-field.

A prvalue of type
char8_t, char16_t, char32_t, or
wchar_t ([basic.fundamental])
(including a converted bit-field that was not
already promoted to int or unsigned int
according to the rules above)
can be converted to a prvalue
of the first of the following types that can represent all the values of
its underlying type:
int,
unsigned int,
long int,
unsigned long int,
long long int,
unsigned long long int, or
its underlying type.

A prvalue of type bool can be converted to a prvalue of type
int, with false becoming zero and true becoming
one.