[Ada] Bit_Order cannot be defined for record extensions

This patch allows the compiler to report an error on Bit_Order when
defined for a record extension.

2018-07-16  Javier Miranda  <miranda@adacore.com>

gcc/ada/

	* sem_ch13.adb (Analyze_Attribute_Definition_Clause): Report an error
	on Bit_Order when defined for a record extension.

gcc/testsuite/

	* gnat.dg/bit_order1.adb: New testcase.

From-SVN: r262712

gcc/ada/ChangeLog

+2018-07-16  Javier Miranda  <miranda@adacore.com>
+
+	* sem_ch13.adb (Analyze_Attribute_Definition_Clause): Report an error
+	on Bit_Order when defined for a record extension.
+
 2018-07-16  Arnaud Charlet  <charlet@adacore.com>
 
 	* libgnat/s-objrea.ads: Minor code clean up.

gcc/ada/sem_ch13.adb

@@ -5331,6 +5331,12 @@ package body Sem_Ch13 is
                Error_Msg_N
                  ("Bit_Order can only be defined for record type", Nam);
 
+            elsif Is_Tagged_Type (U_Ent)
+               and then Is_Derived_Type (U_Ent)
+            then
+               Error_Msg_N
+                 ("Bit_Order cannot be defined for record extensions", Nam);
+
             elsif Duplicate_Clause then
                null;
 

gcc/testsuite/ChangeLog

 2018-07-16  Javier Miranda  <miranda@adacore.com>
 
+	* gnat.dg/bit_order1.adb: New testcase.
+
+2018-07-16  Javier Miranda  <miranda@adacore.com>
+
 	* gnat.dg/iter2.adb, gnat.dg/iter2.ads: New testcase.
 
 2018-07-16  Richard Biener  <rguenther@suse.de>

gcc/testsuite/gnat.dg/bit_order1.adb

+--  { dg-do compile }
+
+with System;
+
+procedure Bit_Order1 is
+
+   type Sample_Ttype is tagged record
+      Data : Natural;
+   end record;
+
+   type Other_Type is new Sample_Ttype with record
+      Other_Data : String (1 .. 100);
+   end record;
+
+   for Other_Type'Bit_Order use System.High_Order_First; --  { dg-error "Bit_Order cannot be defined for record extensions" }
+begin
+   null;
+end;