[Ada] Avoid compiler crash for body in non Ada 2012 mode

2018-05-21  Javier Miranda  <miranda@adacore.com>

gcc/ada/

	* sem_ch4.adb (Analyze_Membership_Op): Avoid compiler crash when the
	spec of a unit has Ada 2012 membership tests with multiple choices and
	the unit body is not compiled under Ada 2012 mode.

From-SVN: r260464

gcc/ada/ChangeLog

+2018-04-04  Javier Miranda  <miranda@adacore.com>
+
+	* sem_ch4.adb (Analyze_Membership_Op): Avoid compiler crash when the
+	spec of a unit has Ada 2012 membership tests with multiple choices and
+	the unit body is not compiled under Ada 2012 mode.
+
 2018-04-04  Doug Rupp  <rupp@adacore.com>
 
 	* sigtramp-vxworks-target.inc: Set cfa_reg properly from sigcontext

gcc/ada/sem_ch4.adb

@@ -3030,9 +3030,15 @@ package body Sem_Ch4 is
    begin
       Analyze_Expression (L);
 
-      if No (R) and then Ada_Version >= Ada_2012 then
-         Analyze_Set_Membership;
-         Check_Function_Writable_Actuals (N);
+      if No (R) then
+         if Ada_Version >= Ada_2012 then
+            Analyze_Set_Membership;
+            Check_Function_Writable_Actuals (N);
+         else
+            Error_Msg_N
+              ("multiple choices in membership tests only allowed in Ada 2012",
+               N);
+         end if;
 
          return;
       end if;