[gcc r13-502] [Ada] Fix fallout of change in equality for untagged record types

[Pierre-Marie de Rodat <pmderodat@gcc.gnu.org>]

https://gcc.gnu.org/g:b90e43dbbb2ba00ef2f8b2468fb09b43a12ae13d

commit r13-502-gb90e43dbbb2ba00ef2f8b2468fb09b43a12ae13d
Author: Eric Botcazou <ebotcazou@adacore.com>
Date:   Wed Mar 16 14:50:24 2022 +0100

    [Ada] Fix fallout of change in equality for untagged record types
    
    The problem is that the resolution of expanded names implicitly assumes
    that the visible and private homonyms in a given scope are segregated on
    the homonym chain, and this was no longer the case for equality operators
    in the specific case at stake.
    
    gcc/ada/
    
            * sem_ch7.adb (Inspect_Untagged_Record_Completion): Also move the
            equality operator on the homonym chain if there is another equality
            operator in the private part.

Diff:
---
 gcc/ada/sem_ch7.adb | 30 +++++++++++++++++++++++++++---
 1 file changed, 27 insertions(+), 3 deletions(-)

diff --git a/gcc/ada/sem_ch7.adb b/gcc/ada/sem_ch7.adb
index 4ba1d32cf7c..0b11176793c 100644
--- a/gcc/ada/sem_ch7.adb
+++ b/gcc/ada/sem_ch7.adb
@@ -1491,6 +1491,7 @@ package body Sem_Ch7 is
                   Prim_List : constant Elist_Id :=
                      Collect_Primitive_Operations (Defining_Identifier (Decl));
 
+                  E       : Entity_Id;
                   Ne_Id   : Entity_Id;
                   Op_Decl : Node_Id;
                   Op_Id   : Entity_Id;
@@ -1517,16 +1518,39 @@ package body Sem_Ch7 is
                         pragma Assert (Ekind (Ne_Id) = E_Function
                           and then Corresponding_Equality (Ne_Id) = Op_Id);
 
+                        E := First_Private_Entity (Id);
+
                         --  Move them from the private part of the entity list
                         --  up to the end of the visible part of the same list.
 
                         Remove_Entity (Op_Id);
                         Remove_Entity (Ne_Id);
 
-                        Link_Entities
-                          (Prev_Entity (First_Private_Entity (Id)), Op_Id);
+                        Link_Entities (Prev_Entity (E), Op_Id);
                         Link_Entities (Op_Id, Ne_Id);
-                        Link_Entities (Ne_Id, First_Private_Entity (Id));
+                        Link_Entities (Ne_Id, E);
+
+                        --  And if the private part contains another equality
+                        --  operator, move the equality operator to after it
+                        --  in the homonym chain, so that all its next homonyms
+                        --  in the same scope, if any, also are in the visible
+                        --  part. This is relied upon to resolve expanded names
+                        --  in Collect_Interps for example.
+
+                        while Present (E) loop
+                           exit when Ekind (E) = E_Function
+                             and then Chars (E) = Name_Op_Eq;
+
+                           Next_Entity (E);
+                        end loop;
+
+                        if Present (E) then
+                           Remove_Homonym (Op_Id);
+
+                           Set_Homonym (Op_Id, Homonym (E));
+                           Set_Homonym (E, Op_Id);
+                        end if;
+
                         exit;
                      end if;