The prefix of the Has_Access_Values attribute is a type. The result
is a Boolean value which is True if the is an access type, or is a composite
type with a component (at any nesting depth) that is an access type, and is
False otherwise.
The intended use of this attribute is in conjunction with generic
definitions. If the attribute is applied to a generic private type, it
indicates whether or not the corresponding actual type has access values.