<xstd/ints/type_traits/promoted.hpp>

xstd::promoted_t

template<class T>
using promoted_t = see below;

The type of a T operand after integral promotion.

promoted_t<T> is the type of +a for an lvalue a of type const T where T is std::integral, which is what [conv.prom] gives, and T otherwise. Narrow built-ins promote to int, or to int or unsigned as the platform decides, bool to int, and int and wider are their own; a cv-qualified type promotes as the unqualified type does, short const to int.

Notes

• A non-integral type's own operator+ is never asked: decltype(+a) is formed only for an integral T.
• For an integer-class type it is the type itself, which the closure requirements of integer_class rely on, and so it is for a bit-precise type, which is exempt from integral promotion whichever branch it takes: uint128, absl::uint128, bit_uint<17> and bit_int<9> are their own.
• It keeps every signed exact-width type signed.

See also

Entity	Relation
integer_class	states its closure requirements against it
bit_mask	states its operators' results against it
boost::integral_promotion_t	Boost.TypeTraits' counterpart, which keeps cv-qualifiers, promotes enumerations and leaves char8_t, char16_t and char32_t alone