A value of integral or enumeration type can be explicitly converted to a complete enumeration type. If the enumeration type has a fixed underlying type, the value is first converted to that type by integral conversion, if necessary, and then to the enumeration type.

Consider this example

enum A:int{};
char c = 0;
A a = static_cast<A>(c);

One integral type with a less integer conversion rank converts to another integral type with a greater integer conversion rank is considered Integral promotion, while Integral conversion does explicitly state that

The conversions allowed as integral promotions are excluded from the set of integral conversions.

I think we should need to add Integral promotion into [expr.static.cast#10] if such a conversion is necessary. It also should be the intent here.