This patch enforces the same semantics for the handling of loop parameters
in element iterators over formal containers, os those over formal containers:
the loop parameter cannot be assigned to in user code.
Compiling formal_test.adb must yield:
formal_test.adb:15:07: assignment to loop parameter not allowed
---
with Ada.Containers.Formal_Doubly_Linked_Lists;
procedure Formal_Test is
type E is range 1 .. 1000;
package My_List is new Ada.Containers.Formal_Doubly_Linked_Lists (E);
use My_List;
Thing : My_List.List (10);
C : Cursor;
begin
for I in 1 .. 10 loop
Append (Thing, E (I));
end loop;
for Element of Thing loop
null;
Element := Element * 3; -- ERROR
end loop;
end;
Tested on x86_64-pc-linux-gnu, committed on trunk
2014-10-10 Ed Schonberg <schonb...@adacore.com>
* exp_ch5.adb (Expand_Formal_Container_Element_Loop): Analyze
declaration for loop parameter before rest of loop, and set
entity kind to prevent assignments to it in the user code.
* sem_ch3.adb (Analyze_Object_Contract): No contracts apply to the
loop parameter in an element iteration over o formal container.
Index: exp_ch5.adb
===================================================================
--- exp_ch5.adb (revision 216063)
+++ exp_ch5.adb (working copy)
@@ -2889,7 +2889,17 @@
Statements => New_List (New_Loop)));
Rewrite (N, New_Loop);
- Analyze (New_Loop);
+
+ -- The loop parameter is declared by an object declaration, but within
+ -- the loop we must prevent user assignments to it, so we analyze the
+ -- declaration and reset the entity kind, before analyzing the rest of
+ -- the loop;
+
+ Analyze (Elmt_Decl);
+ Set_Ekind (Defining_Identifier (Elmt_Decl), E_Loop_Parameter);
+ Set_Assignment_OK (Name (Elmt_Ref));
+
+ Analyze (N);
end Expand_Formal_Container_Element_Loop;
-----------------------------
Index: sem_ch3.adb
===================================================================
--- sem_ch3.adb (revision 216063)
+++ sem_ch3.adb (working copy)
@@ -3062,6 +3062,12 @@
Error_Msg_N ("constant cannot be volatile", Obj_Id);
end if;
+ -- The loop parameter in an element iterator over a formal container
+ -- is declared with an object declaration but no contracts apply.
+
+ elsif Ekind (Obj_Id) = E_Loop_Parameter then
+ null;
+
else pragma Assert (Ekind (Obj_Id) = E_Variable);
-- The following checks are only relevant when SPARK_Mode is on as
