Fix internal error on function returning dynamically-sized type

This is a tree sharing issue for the internal return type synthesized for
a function returning a dynamically-sized type and taking an Out or In/Out
parameter passed by copy.

gcc/ada/
	* gcc-interface/decl.cc (gnat_to_gnu_subprog_type): Also create a
	TYPE_DECL for the return type built for the CI/CO mechanism.

gcc/testsuite/
	* gnat.dg/varsize4.ads, gnat.dg/varsize4.adb: New test.
	* gnat.dg/varsize4_pkg.ads: New helper.

3 files changed, 33 insertions, 0 deletions

diff --git a/gcc/testsuite/gnat.dg/varsize4.adb b/gcc/testsuite/gnat.dg/varsize4.adb
new file mode 100644
index 0000000..3d0430d
--- /dev/null
+++ b/gcc/testsuite/gnat.dg/varsize4.adb
@@ -0,0 +1,19 @@
+-- { dg-do compile }
+
+package body Varsize4 is
+
+   function Func (bytes_read : out Natural) return Arr is
+      Ret : Arr := (others => False);
+   begin
+      return Ret;
+   end;
+
+   function Get return Natural is
+      Data  : Arr;
+      Bytes : Natural;
+   begin
+      Data := Func (Bytes);
+      return Bytes;
+   end;
+
+end Varsize4;
diff --git a/gcc/testsuite/gnat.dg/varsize4.ads b/gcc/testsuite/gnat.dg/varsize4.ads
new file mode 100644
index 0000000..62b673f
--- /dev/null
+++ b/gcc/testsuite/gnat.dg/varsize4.ads
@@ -0,0 +1,9 @@
+with Varsize4_Pkg;
+
+package Varsize4 is
+
+   type Arr is array (1 .. Varsize4_Pkg.F) of Boolean;
+
+   function Get return Natural;
+
+end Varsize4;
diff --git a/gcc/testsuite/gnat.dg/varsize4_pkg.ads b/gcc/testsuite/gnat.dg/varsize4_pkg.ads
new file mode 100644
index 0000000..e07a6b0
--- /dev/null
+++ b/gcc/testsuite/gnat.dg/varsize4_pkg.ads
@@ -0,0 +1,5 @@
+package Varsize4_Pkg is
+
+   function F return Natural;
+
+end Varsize4_Pkg;