Rough proposal to make some generic types static

[Victor Porton <porton@narod.ru>]

What in the RM signifies that Enum_Type (below) is not a static scalar
type?

We should work on an amendment for a future version of Ada to make
Enum_Type static.

Is it difficult to implement this?

Rationale is that the below code is useful in practice.

gnatmake -q -c -gnatc -u -P/home/porton/Projects/redland-bindings/ada/test.gpr -XRUNTIME=full -XMODE=Install rdf-auxilary.adb
rdf-auxilary.adb:7:25: non-static expression used for modular type bound
rdf-auxilary.adb:7:38: size attribute is only static for static scalar type (RM 4.9(7,8))

-- rdf.ads
package RDF is
end RDF;

-- rdf-auxilary.ads
with Interfaces.C;

package RDF.Auxilary is

   generic
      type Enum_Type is (<>);
   package Convert_Enum is
      function To_C(Argument: Enum_Type) return Interfaces.C.int;
      function From_C(Argument: Interfaces.C.int) return Enum_Type;
   end;

end RDF.Auxilary;

-- rdf-auxilary.adb
with Ada.Unchecked_Conversion;

package body RDF.Auxilary is

   package body Convert_Enum is

      type Small is mod 2**(Enum_Type'Size);

      function To_C_Internal is
        new Ada.Unchecked_Conversion (Source => Enum_Type, Target => Small);

      function From_C_Internal is
        new Ada.Unchecked_Conversion (Source => Small, Target => Enum_Type);

      function To_C(Argument: Enum_Type) return Interfaces.C.int is
      begin
         return Interfaces.C.int(To_C_Internal(Argument));
      end;

      function From_C(Argument: Interfaces.C.int) return Enum_Type is
      begin
         return From_C_Internal(Small(Argument));
      end;

   end;

end RDF.Auxilary;


-- 
Victor Porton - http://portonvictor.org