[Ada] Assertion failure on Default_Initial_Condition

[Pierre-Marie de Rodat]

This patch prevents the association of a Default_Initial_Condition with
an incomplete type whose full view is the private type or private
extension subject to the aspect/pragma.

Tested on x86_64-pc-linux-gnu, committed on trunk

2019-07-04  Hristian Kirtchev  <kirtc...@adacore.com>

gcc/ada/

        * sem_util.adb (Propagate_DIC_Attributes): Do not propagate the
        Default_Initial_Condition attributes to an incomplete type.

gcc/testsuite/

        * gnat.dg/default_initial_condition.adb,
        gnat.dg/default_initial_condition_pack.adb,
        gnat.dg/default_initial_condition_pack.ads: New testcase.
--- gcc/ada/sem_util.adb
+++ gcc/ada/sem_util.adb
@@ -23327,6 +23327,13 @@ package body Sem_Util is
 
          if From_Typ = Typ then
             return;
+
+         --  Nothing to do when the destination denotes an incomplete type
+         --  because the DIC is associated with the current instance of a
+         --  private type, thus it can never apply to an incomplete type.
+
+         elsif Is_Incomplete_Type (Typ) then
+            return;
          end if;
 
          DIC_Proc := DIC_Procedure (From_Typ);

--- /dev/null
new file mode 100644
+++ gcc/testsuite/gnat.dg/default_initial_condition.adb
@@ -0,0 +1,12 @@
+--  { dg-do run }
+--  { dg-options "-gnata" }
+
+with Default_Initial_Condition_Pack; use Default_Initial_Condition_Pack;
+
+procedure Default_Initial_Condition is
+   Obj : T;
+begin
+   if not DIC_Called then
+      raise Program_Error;
+   end if;
+end Default_Initial_Condition;

--- /dev/null
new file mode 100644
+++ gcc/testsuite/gnat.dg/default_initial_condition_pack.adb
@@ -0,0 +1,7 @@
+package body Default_Initial_Condition_Pack is
+   function Is_OK (Val : T) return Boolean is
+   begin
+      DIC_Called := True;
+      return True;
+   end Is_OK;
+end Default_Initial_Condition_Pack;

--- /dev/null
new file mode 100644
+++ gcc/testsuite/gnat.dg/default_initial_condition_pack.ads
@@ -0,0 +1,12 @@
+package Default_Initial_Condition_Pack is
+   type T;
+   type T is private
+     with Default_Initial_Condition => Is_OK (T);
+
+   function Is_OK (Val : T) return Boolean;
+
+   DIC_Called : Boolean := False;
+
+private
+   type T is null record;
+end Default_Initial_Condition_Pack;