CVS difference for ai05s/ai05-0164-1.txt

--- ai05s/ai05-0164-1.txt	2009/10/22 04:25:37	1.1
+++ ai05s/ai05-0164-1.txt	2009/10/23 06:06:31	1.2
@@ -1,4 +1,4 @@
-!standard 3.4(xx)                                   09-10-21  AI05-0164-1/01
+!standard 3.4(18/2)                                   09-10-21  AI05-0164-1/01
 !standard 6.1(27.1/2)
 !class binding interpretation 09-10-21
 !status work item 09-10-21
@@ -237,6 +237,73 @@
 the overriding procedure Pack2.Op is called, and that procedure thinks it's
 calling a function that returns something of type T1 when it isn't.  This cannot
 be good.
+
+****************************************************************
+
+From: Christoph Grein
+Sent: Wednesday, June 24, 2009  2:37 AM
+
+        overriding
+        procedure Op (Obj   : in out T1;
+                      Count : in Integer;
+                      Func  : access function (Obj : in T1) return T1);
+
+GNAT Pro 6.2.1 says: subprogram Op is not overriding.
+
+This is accepted as overriding, but it leads of course to problems in the body:
+
+  procedure Op (Obj  : in out T1;
+                Count: in Integer;
+                Func : access function (Obj: in Pack_0.Root) return Pack_0.Root);
+
+****************************************************************
+
+From: Adam Beneschan
+Sent: Wednesday, June 24, 2009  9:40 AM
+
+>         overriding
+>         procedure Op (Obj   : in out T1;
+>                       Count : in Integer;
+>                       Func  : access function (Obj : in T1) return T1);
+> 
+> GNAT Pro 6.2.1 says: subprogram Op is not overriding.
+
+I'm not surprised.  I'm guessing that T1 is derived from Root, and GNAT
+implicitly declares the subprogram inherited from this one:
+
+        procedure Op (Obj   : in out Root;
+                      Count : in Integer;
+                      Func  : access function (Obj : in Root) return Root);
+
+it replaces "Root" by "T1" in the profile, but when doing so, it fails to go
+into the profile of the access-subprogram parameter, resulting in this inherited
+subprogram:
+
+        procedure Op (Obj   : in out T1;
+                      Count : in Integer;
+                      Func  : access function (Obj : in Root) return Root);
+
+So then of course it would reject the above declaration as "overriding" (and
+accept this one:)
+
+
+> This is accepted as overriding, but it leads of course to problems in 
+> the body:
+> 
+>   procedure Op (Obj  : in out T1;
+>                 Count: in Integer;
+>                 Func : access function (Obj: in Pack_0.Root) return 
+> Pack_0.Root);
+
+Our compiler has the same behavior.
+
+However, I believe GNAT (like our compiler) is doing the wrong thing, based on the
+wording of the RM.  It could be that the wording of the RM doesn't reflect what is
+intended, and that "systematically replacing subtypes of the profile" isn't supposed
+to include subtypes in an access-subprogram-parameter profile.  If that's the case,
+the RM needs to be changed, and then GNAT will be right without making any changes.
+But as it currently stands, unless there is some other applicable rule I missed, the
+compilers are not following the RM.
 
 ****************************************************************