A subtype is created from the renamed object in an object renaming declaration
with an unconstrained nominal subtype. That subtype must be frozen ahead of
the renaming declaration, to prevent order of elaboration issues when the
nominal subtype of the object has unknown discriminants. The renamed object
itself has already frozen the type.
The following must compile quietly in ada 2012 mode:
with Q;
procedure P is
subtype Name is String
with Dynamic_Predicate => (for all C of Name => C not in 'a'..'z');
package My_Q is new Q (Name);
begin
null;
end;
---
generic
type Key_Type (<>) is private;
package Q is
type Key_Access is access Key_Type;
type Cursor is record
Key : Key_Access;
end record;
procedure Query_Element (Position : Cursor);
end Q;
---
package body Q is
procedure Query_Element (Position : Cursor) is
K : Key_Type renames Position.Key.all;
begin
null;
end;
end Q;
Tested on x86_64-pc-linux-gnu, committed on trunk
2013-04-11 Ed Schonberg <schonb...@adacore.com>
* sem_ch8.adb (Check_Constrained_Object): If a subtype is created
from the renamed object in an object renaming declaration with
an unconstrained nominal subtype, freeze the created subtype at
once, to prevent order of elaboration issues in the backend.
Index: sem_ch8.adb
===================================================================
--- sem_ch8.adb (revision 197746)
+++ sem_ch8.adb (working copy)
@@ -792,6 +792,12 @@
Make_Subtype_From_Expr (Nam, Typ)));
Rewrite (Subtype_Mark (N), New_Occurrence_Of (Subt, Loc));
Set_Etype (Nam, Subt);
+
+ -- Freeze subtype at once, to prevent order of elaboration
+ -- issues in the backend. The renamed object exists, so its
+ -- type is already frozen in any case.
+
+ Freeze_Before (N, Subt);
end if;
end if;
end Check_Constrained_Object;
