12.5.4 Formal Access Types

The class determined for a formal access type is the class of all access types.
Syntax

formal_access_type_definition ::= access_type_definition

Legality Rules

For a formal access-to-object type, the designated subtypes of the formal and actual types shall statically match.
If and only if the general_access_modifier constant applies to the formal, the actual shall be an access-to-constant type. If the general_access_modifier all applies to the formal, then the actual shall be a general access-to-variable type, See section 3.10 Access Types.
For a formal access-to-subprogram subtype, the designated profiles of the formal and the actual shall be mode-conformant, and the calling convention of the actual shall be protected if and only if that of the formal is protected.
Examples
Example of formal access types:

--  the formal types of the generic package

generic
   type Node is private;
   type Link is access Node;
package P is
   ...
end P;

type Car is
   record
      Pred, Succ : Car_Name;
      Number     : License_Number;
      Owner      : Person;
   end record;

--  in the following generic instantiation

package R is new P(Node => Car, Link => Car_Name);