https://gcc.gnu.org/g:e94fe9439a690912e79e4cdb9ba4a8287e0749f7
commit r16-2340-ge94fe9439a690912e79e4cdb9ba4a8287e0749f7
Author: Steve Baird <ba...@adacore.com>
Date: Thu Jun 26 12:23:53 2025 -0700
ada: Spurious actual/formal matching check failure for formal derived type.
In some cases involving a generic with two formal parameters, a formal
package
and a formal derived type that is derived from an interface type declared in
the formal package, a legal instantiation of that generic is rejected with a
message incorrectly stating that the second actual parameter does not
implement
the required interface.
gcc/ada/ChangeLog:
* sem_ch12.adb (Validate_Derived_Type_Instance): Cope with the case
where the ancestor type for a formal derived type is declared in
an earlier formal package but Get_Instance_Of does not return the
corresponding type from the corresponding actual package.
Diff:
---
gcc/ada/sem_ch12.adb | 17 +++++++++++++++--
1 file changed, 15 insertions(+), 2 deletions(-)
diff --git a/gcc/ada/sem_ch12.adb b/gcc/ada/sem_ch12.adb
index e80aea5fe762..1cb9d115cc58 100644
--- a/gcc/ada/sem_ch12.adb
+++ b/gcc/ada/sem_ch12.adb
@@ -14371,8 +14371,21 @@ package body Sem_Ch12 is
elsif
Scope (Scope (Base_Type (Etype (A_Gen_T)))) = Scope (A_Gen_T)
then
- Ancestor :=
- Get_Instance_Of (Base_Type (Etype (A_Gen_T)));
+ declare
+ Formal_Ancestor : constant Entity_Id :=
+ Base_Type (Etype (A_Gen_T));
+ begin
+ Ancestor := Get_Instance_Of (Formal_Ancestor);
+
+ -- Handle (rare) case where Get_Instance_Of found nothing in
+ -- the map.
+
+ if Ancestor = Formal_Ancestor then
+ Ancestor :=
+ Get_Instance_Of
+ (Base_Type (Etype (Get_Instance_Of (A_Gen_T))));
+ end if;
+ end;
-- The type may be a local derivation, or a type extension of a
-- previous formal, or of a formal of a parent package.
