[gcc r13-1448] [Ada] Fix dispatching call to primitive function with controlling tagged result

[gcc r13-1448] [Ada] Fix dispatching call to primitive function with controlling tagged result

[Pierre-Marie de Rodat]

https://gcc.gnu.org/g:1f03b43fc7552fe105d33612b3b89b4f0b222798

commit r13-1448-g1f03b43fc7552fe105d33612b3b89b4f0b222798
Author: Eric Botcazou <ebotcazou@adacore.com>
Date:   Thu Jun 2 00:45:14 2022 +0200

    [Ada] Fix dispatching call to primitive function with controlling tagged result
    
    When a dispatching call is made to a primitive function with a controlling
    tagged result, the call is dispatching on result and thus must return the
    class-wide type of the tagged type to accommodate all possible results.
    
    This was ensured by Expand_Dispatching_Call only in the common case where
    the result type is the type of the controlling argument, which does not
    cover the case of a primitive function inherited from an ancestor type.
    
    gcc/ada/
    
            * exp_disp.adb (Expand_Dispatching_Call): Fix detection of calls
            that are dispatching on tagged result.

Diff:
---
 gcc/ada/exp_disp.adb | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/gcc/ada/exp_disp.adb b/gcc/ada/exp_disp.adb
index 17043d15510..3ac4b3b4398 100644
--- a/gcc/ada/exp_disp.adb
+++ b/gcc/ada/exp_disp.adb
@@ -896,8 +896,14 @@ package body Exp_Disp is
       Copy_Strub_Mode (Subp_Typ, Subp);
       Set_Convention  (Subp_Typ, Convention (Subp));
 
-      if Etype (Subp) = Typ then
-         Set_Etype          (Subp_Typ, CW_Typ);
+      --  If this is a function and it has a controlling tagged result, then
+      --  the call is dispatching on result and returns the class-wide type.
+
+      if Ekind (Subp) = E_Function
+        and then Has_Controlling_Result (Subp)
+        and then Is_Tagged_Type (Etype (Subp))
+      then
+         Set_Etype          (Subp_Typ, Class_Wide_Type (Etype (Subp)));
          Set_Returns_By_Ref (Subp_Typ, True);
       else
          Set_Etype          (Subp_Typ, Etype (Subp));