Ada: Fix spurious visibility issue with qualified aggregate in instantiation

Aggregates used as actuals of formal object parameters are handled specially
by Instantiate_Object in Sem_Ch12 and qualifying them is sufficient to block
this special processing.

gcc/ada/
	PR ada/54178
	* sem_ch12.adb (Instantiate_Object): Strip qualification to detect
	aggregates used as actuals.

gcc/testsuite/
	* gnat.dg/aggr32.adb: New test.
	* gnat.dg/aggr32_pkg.ads: New helper.
	* gnat.dg/aggr32_pkg-child.ads: Likewise.

Author: Eric Botcazou

gcc/ada/sem_ch12.adb

@@ -13223,7 +13223,7 @@ package body Sem_Ch12 is
                --  to capture local names that may be hidden if the generic is
                --  a child unit.
 
-               if Nkind (Actual) = N_Aggregate then
+               if Nkind (Unqualify (Actual)) = N_Aggregate then
                   Preanalyze_And_Resolve (Actual, Typ);
                end if;
 

gcc/testsuite/gnat.dg/aggr32.adb

@@ -0,0 +1,15 @@
+-- { dg-do compile }
+
+with Aggr32_Pkg.Child;
+
+procedure Aggr32 (W, H : Positive) is
+
+  use Aggr32_Pkg;
+
+  package Test_1 is new Child (Frame => (Width => W, Height => H));
+
+  package Test_2 is new Child (Frame => Rec'(Width => W, Height => H));
+
+begin
+  null;
+end;

gcc/testsuite/gnat.dg/aggr32_pkg-child.ads

@@ -0,0 +1,6 @@
+generic
+
+  Frame : Rec;
+
+package Aggr32_Pkg.Child is
+end Aggr32_Pkg.Child;

gcc/testsuite/gnat.dg/aggr32_pkg.ads

@@ -0,0 +1,8 @@
+package Aggr32_Pkg is
+
+  type Rec is record
+    Width  : Positive;
+    Height : Positive;
+  end record;
+
+end Aggr32_Pkg;