re PR ada/29015 (Ada 2005 observer pattern with mutually dependent packages and containers produces compiler error)

gcc/ada/
	PR ada/29015
	* sem_ch12.adb (Instantiate_Type): Check whether the full view of
	the type is known instead of the underlying type.

    gcc/testsuite/
	PR ada/29015
	* gnat.dg/incomplete1.ads, gnat.dg/incomplete2.ads,
	gnat.dg/incomplete2.adb: New.

From-SVN: r134345

gcc/ada/ChangeLog

@@ -1,3 +1,9 @@
+2008-04-16  Samuel Tardieu  <sam@rfc1149.net>
+
+	PR ada/29015
+	* sem_ch12.adb (Instantiate_Type): Check whether the full view of
+	the type is known instead of the underlying type.
+
 2008-04-15  Ed Schonberg  <schonberg@adacore.com>
 
 	PR ada/22387

gcc/ada/sem_ch12.adb

@@ -9990,7 +9990,7 @@ package body Sem_Ch12 is
                          Ekind (Root_Type (Act_T)) = E_Incomplete_Type)
          then
             if Is_Class_Wide_Type (Act_T)
-              or else No (Underlying_Type (Act_T))
+              or else No (Full_View (Act_T))
             then
                Error_Msg_N ("premature use of incomplete type", Actual);
                Abandon_Instantiation (Actual);

gcc/testsuite/ChangeLog

@@ -1,3 +1,9 @@
+2008-04-16  Samuel Tardieu  <sam@rfc1149.net>
+
+	PR ada/29015
+	* gnat.dg/incomplete1.ads, gnat.dg/incomplete2.ads,
+	gnat.dg/incomplete2.adb: New.
+
 2008-04-16  Hans-Peter Nilsson  <hp@axis.com>
 
 	PR tree-optimization/35629

gcc/testsuite/gnat.dg/incomplete1.ads

@@ -0,0 +1,3 @@
+package Incomplete1 is
+   type T is null record;
+end Incomplete1;

gcc/testsuite/gnat.dg/incomplete2.adb

@@ -0,0 +1,4 @@
+-- { dg-do compile }
+-- { dg-excess-errors "instantiation abandoned" }
+with Incomplete1;
+package body Incomplete2 is end Incomplete2;

gcc/testsuite/gnat.dg/incomplete2.ads

@@ -0,0 +1,8 @@
+limited with Incomplete1;
+package Incomplete2 is
+   pragma Elaborate_Body;
+   generic
+      type T is private;
+   package G is end G;
+   package I1 is new G (Incomplete1.T); -- { dg-error "premature use" }
+end Incomplete2;