[Bug ada/123289] New: Overloaded subprograms are not correctly resolved within container aggregates

[liam at liampwll dot com via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=123289

            Bug ID: 123289
           Summary: Overloaded subprograms are not correctly resolved
                    within container aggregates
           Product: gcc
           Version: 15.2.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: ada
          Assignee: unassigned at gcc dot gnu.org
          Reporter: liam at liampwll dot com
                CC: dkm at gcc dot gnu.org
  Target Milestone: ---

Within a container aggregate, the Add_Named procedure (and likely all others)
always resolve to the last defined subprogram rather than the subprogram which
matches the argument types. I have tested this on 15.2.1 and the current trunk.
This can be observed using the following test program:

------  json.ads

pragma Ada_2022;

package JSON is
   type JSON_Value is tagged null record;
   type JSON_Object is new JSON_Value with null record
   with Aggregate => (Empty => Empty, Add_Named => Insert);
   type JSON_Integer is new JSON_Value with null record
   with Integer_Literal => From_Universal_Image;

   function Empty return JSON_Object
   is (null record);

   procedure Insert
      (O : in out JSON_Object; Key : String; Value : JSON_Integer'Class)
   is null;
   --  JSON_Integer'Class may be replaced with Integer and the same bug still
occurs.

   procedure Insert (O : in out JSON_Object; Key : String; Value : String)
   is null;

   function From_Universal_Image (Value : String) return JSON_Integer
   is (null record);
end JSON;

-----  example.adb

with JSON; use JSON;

procedure Example is
   A : JSON_Object := ["a" => "b"];
   --  Works if Insert for String is last.

   B : JSON_Object := ["a" => 1];
   --  Works if Insert for JSON_Integer'Class is last.
begin
   A.Insert ("c", 1);
   A.Insert ("d", "e");
   --  Both of these always work.
end Example;