[Ada] Fix bogus component visibility error for class-wide type in generic

[Eric Botcazou]

The problem is that Analyze_Overloaded_Selected_Component does:

            --  If the prefix is a class-wide type, the visible components are
            --  those of the base type.

            if Is_Class_Wide_Type (T) then
               T := Etype (T);
            end if;

and Resolve_Selected_Component does:

               --  The visible components of a class-wide type are those of
               --  the root type.

               if Is_Class_Wide_Type (T) then
                  T := Etype (T);
               end if;

while Analyze_Selected_Component does:

      --  For class-wide types, use the entity list of the root type

      if Is_Class_Wide_Type (Prefix_Type) then
         Type_To_Use := Root_Type (Prefix_Type);
      end if;

when faced with a selected component.  So the 3rd goes to the root type, the 
1st to the base type, and the 2nd wants to do like the 3rd but ends up doing 
like the 1st!  This does not change anything for the class-wide type itself, 
but does for its class-wide subtypes.  The correct processing is the 3rd.

Tested on x86-64/Linux, applied on the mainline.


2025-12-22  Eric Botcazou  <ebotca...@adacore.com>

        PR ada/123185
        * sem_ch4.adb (Analyze_Overloaded_Selected_Component): Go to the
        root when the prefix has a class-wide type.
        * sem_res.adb (Resolve_Selected_Component): Likewise.


2025-12-22  Eric Botcazou  <ebotca...@adacore.com>

        * gnat.dg/specs/class_wide1.ads: New test.

-- 
Eric Botcazou
diff --git a/gcc/ada/sem_ch4.adb b/gcc/ada/sem_ch4.adb
index 8d9270dab50..fa98d120a74 100644
--- a/gcc/ada/sem_ch4.adb
+++ b/gcc/ada/sem_ch4.adb
@@ -4479,16 +4479,16 @@ package body Sem_Ch4 is
             T := It.Typ;
          end if;
 
-         --  Locate the component. For a private prefix the selector can denote
-         --  a discriminant.
+         --  Find the selected component. For a private prefix, the selector
+         --  can denote a discriminant.
 
          if Is_Record_Type (T) or else Is_Private_Type (T) then
 
-            --  If the prefix is a class-wide type, the visible components are
-            --  those of the base type.
+            --  If the prefix has a class-wide type, the visible components are
+            --  those of the root type.
 
             if Is_Class_Wide_Type (T) then
-               T := Etype (T);
+               T := Root_Type (T);
             end if;
 
             Comp := First_Entity (T);
diff --git a/gcc/ada/sem_res.adb b/gcc/ada/sem_res.adb
index 14dd9ade235..bfbfc109944 100644
--- a/gcc/ada/sem_res.adb
+++ b/gcc/ada/sem_res.adb
@@ -11454,16 +11454,16 @@ package body Sem_Res is
                T := It.Typ;
             end if;
 
-            --  Locate selected component. For a private prefix the selector
+            --  Find the selected component. For a private prefix, the selector
             --  can denote a discriminant.
 
             if Is_Record_Type (T) or else Is_Private_Type (T) then
 
-               --  The visible components of a class-wide type are those of
-               --  the root type.
+               --  If the prefix has a class-wide type, the visible components
+               --  are those of the root type.
 
                if Is_Class_Wide_Type (T) then
-                  T := Etype (T);
+                  T := Root_Type (T);
                end if;
 
                Comp := First_Entity (T);

-- { dg-do compile }

with Ada.Containers.Indefinite_Vectors;

generic
package Class_Wide1 is

   type R is tagged record
      X : Integer;
   end record;

   package V is new Ada.Containers.Indefinite_Vectors (Positive, R);
   package V_CW is new Ada.Containers.Indefinite_Vectors (Positive, R'Class);

   function F1 (VV : V.Vector) return Integer is (VV (1).X);
   function F2 (VV : V_CW.Vector) return Integer is (VV (1).Element.X);
   function F3 (VV : V_CW.Vector) return Integer is (VV (1).X);

end Class_Wide1;