[COMMITTED] ada: Fix assertion failure on very peculiar enumeration type

["Marc Poulhiès" <poulhies@adacore.com>]

From: Eric Botcazou <ebotcazou@adacore.com>

The compiler currently does not support the combination of a representation
clause on an enumeration type with a size clause whose value is greater than
the size of the largest machine scalar supported by the target.

Given that such a type would have little practical value, this change causes
the compiler to give a proper error message instead of aborting.

gcc/ada/

	* freeze.adb (Freeze_Enumeration_Type): Give an error on a type with
	both representation clause and too large size.

Tested on x86_64-pc-linux-gnu, committed on master.

---
 gcc/ada/freeze.adb | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/gcc/ada/freeze.adb b/gcc/ada/freeze.adb
index 38aeb2456ff..0fc33a420c2 100644
--- a/gcc/ada/freeze.adb
+++ b/gcc/ada/freeze.adb
@@ -8023,6 +8023,20 @@ package body Freeze is
 
          Adjust_Esize_For_Alignment (Typ);
       end if;
+
+      --  Reject a very large size on a type with a non-standard representation
+      --  because Expand_Freeze_Enumeration_Type cannot deal with it.
+
+      if Has_Non_Standard_Rep (Typ)
+        and then Known_Esize (Typ)
+        and then Esize (Typ) > System_Max_Integer_Size
+      then
+         Error_Msg_N
+           ("enumeration type with representation clause too large", Typ);
+         Error_Msg_Uint_1 := UI_From_Int (System_Max_Integer_Size);
+         Error_Msg_N
+           ("\the size of such a type cannot exceed ^ bits", Typ);
+      end if;
    end Freeze_Enumeration_Type;
 
    -----------------------
-- 
2.40.0