ada: Private extensions with the keyword "synchronized" are always limited.

GNAT was relying on synchronized private type extensions deriving from a
concurrent interface to determine its limitedness. This does not cover the case
where such an extension derives a limited interface. RM-7.6(6/2) makes is clear
that "synchronized" in a private extension implies the derived type is limited.
GNAT should explicitly check for the presence of "synchronized" in a private
extension declaration, and it should have the same effect as the presence of
“limited”.

gcc/ada/ChangeLog:

	* sem_ch3.adb (Build_Derived_Record_Type): Treat presence of
	keyword "synchronized" the same as "limited" when determining if a
	private extension is limited.

gcc/testsuite/ChangeLog:

	* gnat.dg/sync_tag_discriminals.adb: New test.
	* gnat.dg/sync_tag_limited.adb: New test.

Signed-off-by: Richard Wai <richard@annexi-strayline.com>

1 files changed, 9 insertions, 3 deletions

diff --git a/gcc/ada/sem_ch3.adb b/gcc/ada/sem_ch3.adb
index 3262236..92902a7 100644
--- a/gcc/ada/sem_ch3.adb
+++ b/gcc/ada/sem_ch3.adb
@@ -9599,9 +9599,15 @@ package body Sem_Ch3 is
 
       --  AI-419: Limitedness is not inherited from an interface parent, so to
       --  be limited in that case the type must be explicitly declared as
-      --  limited. However, task and protected interfaces are always limited.
-
-      if Limited_Present (Type_Def) then
+      --  limited, or synchronized. While task and protected interfaces are
+      --  always limited, a synchronized private extension might not inherit
+      --  from such interfaces, and so we also need to recognize the
+      --  explicit limitedness implied by a synchronized private extension
+      --  that does not derive from a synchronized interface (see RM-7.3(6/2)).
+
+      if Limited_Present (Type_Def)
+        or else Synchronized_Present (Type_Def)
+      then
          Set_Is_Limited_Record (Derived_Type);
 
       elsif Is_Limited_Record (Parent_Type)