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From: =?utf-8?Q?Yannick_Duch=C3=AAne_=28Hibou57?=
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Date: Fri, 19 Oct 2012 01:44:29 +0200
Organization: Ada @ Home
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Date: 2012-10-19T01:44:29+02:00
List-Id: <comp.lang.ada>

Is this GNAT doing macro=E2=80=91expansion for generics, or me missing s=
ome trick  =

of Ada 2012?

Small snippet first, then comments below (not Ada comments).


     -- g.ads

     package G is

        pragma Pure;

        type E
           is (E1, E2, E3);

        type I_Type
           is interface;

        function F
          (I : I_Type)
           return E
           is abstract;

        procedure P
          (I : I_Type)
           is abstract
           with Pre'Class =3D> F (I) =3D E1;

     end;


     -- m.adb

     with G;

     procedure M is

        type I_Type
           is new G.I_Type
           with null record;

        overriding function F (I : I_Type) return G.E;
        overriding procedure P (I : I_Type);

        -- subtype E is G.E;
        -- E1 : constant E :=3D G.E1;
        -- use type E;

        function F (I : I_Type) return G.E
           is (G.E1);

        procedure P (I : I_Type) is
           begin null; end;

     begin
        null;
     end;


GNAT can compile package `G`, but while compiling `M`, complains `E1`  =

(from the precondition of `P` in `G`) is not visible in `M`. Un=E2=80=91=
commenting  =

the three initially commented lines solves the issue, but still leave me=
  =

with a feeling, things are going here as if a kind of macro=E2=80=91expa=
nsion was  =

applying. The precondition should be compiled in the context of its  =

definition, isn't it?

Other funny stuff: in the precondition of P, substitute `P (I)` to `F  =

(I)`. GNAT will compile `G` without a complain, and will only figure  =

something is wrong while compiling `M`. Is this GNAT's fault, or mine  =

missing something?

Note: both occur using FSF GNAT 4.6


-- =

=E2=80=9CSyntactic sugar causes cancer of the semi-colons.=E2=80=9D [1]
=E2=80=9CStructured Programming supports the law of the excluded muddle.=
=E2=80=9D [1]
[1]: Epigrams on Programming =E2=80=94 Alan J. =E2=80=94 P. Yale Univers=
ity