[Ada] Crash on Loop_Entry for while_loop involving substrings

When expanding a loop entry attribute for a while_loop we construct a
function that incorporates the expanded condition of the loop. The
itypes that may be generated in that expansion must carry the scope of
the constructed function for proper handling in the backend.

2019-08-20  Ed Schonberg  <schonberg@adacore.com>

gcc/ada/

	* exp_attr.adb (Expand_Loop_Entry_Attribute): When expanding a
	loop entry attribute for a while_loop we construct a function
	that incorporates the expanded condition of the loop. The itypes
	that may be generated in that expansion must carry the scope of
	the constructed function for proper handling in gigi.

gcc/testsuite/

	* gnat.dg/loop_entry2.adb: New testcase.

From-SVN: r274734

gcc/ada/ChangeLog

 2019-08-20  Ed Schonberg  <schonberg@adacore.com>
 
+	* exp_attr.adb (Expand_Loop_Entry_Attribute): When expanding a
+	loop entry attribute for a while_loop we construct a function
+	that incorporates the expanded condition of the loop. The itypes
+	that may be generated in that expansion must carry the scope of
+	the constructed function for proper handling in gigi.
+
+2019-08-20  Ed Schonberg  <schonberg@adacore.com>
+
 	* exp_disp.adb (Build_Class_Wide_Check, Replace_Formals): When a
 	dispatching call tp a subprogram with a class-wide precondition
 	occurrs in the same declarative part as the ancestor subprogram

gcc/ada/exp_attr.adb

@@ -1436,6 +1436,25 @@ package body Exp_Attr is
                Insert_Action (Loop_Stmt, Func_Decl);
                Pop_Scope;
 
+               --  The analysis of the condition may have generated itypes
+               --  that are now used within the function: Adjust their
+               --  scopes accordingly so that their use appears in their
+               --  scope of definition.
+
+               declare
+                  Ityp : Entity_Id;
+
+               begin
+                  Ityp := First_Entity (Loop_Id);
+
+                  while Present (Ityp) loop
+                     if Is_Itype (Ityp) then
+                        Set_Scope (Ityp, Func_Id);
+                     end if;
+                     Next_Entity (Ityp);
+                  end loop;
+               end;
+
                --  Transform the original while loop into an infinite loop
                --  where the last statement checks the negated condition. This
                --  placement ensures that the condition will not be evaluated

gcc/testsuite/ChangeLog

 2019-08-20  Ed Schonberg  <schonberg@adacore.com>
 
+	* gnat.dg/loop_entry2.adb: New testcase.
+
+2019-08-20  Ed Schonberg  <schonberg@adacore.com>
+
 	* gnat.dg/tagged5.adb, gnat.dg/tagged5.ads: New testcase.
 
 2019-08-20  Gary Dismukes  <dismukes@adacore.com>

gcc/testsuite/gnat.dg/loop_entry2.adb

+--  { dg-do compile }
+--  { dg-options "-gnata" }
+
+procedure Loop_Entry2 (S : String) is
+   J : Integer := S'First;
+begin
+   while S(J..J+1) = S(J..J+1) loop
+      pragma Loop_Invariant (for all K in J'Loop_Entry .. J => K <= J);
+      J := J + 1;
+   end loop;
+end;