[C++ PATCH] Diagnose = delete override of a friend function defined earlier (PR c++/80259)

[Jakub Jelinek <jakub@redhat.com>]

Hi!

As the testcase shows, we weren't diagnosing the foo case in the testcase
and would just silently overwrite old DECL_INITIAL with error_mark_node
and ICE later on.  Fixed thusly, bootstrapped/regtested on x86_64-linux
and i686-linux, ok for trunk?

2017-12-01  Jakub Jelinek  <jakub@redhat.com>

	PR c++/80259
	* decl2.c (grokfield): Diagnose = delete redefinition of a friend.

	* g++.dg/cpp0x/pr80259.C: New test.

--- gcc/cp/decl2.c.jj	2017-11-21 08:43:50.000000000 +0100
+++ gcc/cp/decl2.c	2017-12-01 12:01:32.671514761 +0100
@@ -911,9 +911,18 @@ grokfield (const cp_declarator *declarat
 	{
 	  if (init == ridpointers[(int)RID_DELETE])
 	    {
-	      DECL_DELETED_FN (value) = 1;
-	      DECL_DECLARED_INLINE_P (value) = 1;
-	      DECL_INITIAL (value) = error_mark_node;
+	      if (friendp && decl_defined_p (value))
+		{
+		  error ("redefinition of %q#D", value);
+		  inform (DECL_SOURCE_LOCATION (value),
+			  "%q#D previously defined here", value);
+		}
+	      else
+		{
+		  DECL_DELETED_FN (value) = 1;
+		  DECL_DECLARED_INLINE_P (value) = 1;
+		  DECL_INITIAL (value) = error_mark_node;
+		}
 	    }
 	  else if (init == ridpointers[(int)RID_DEFAULT])
 	    {
--- gcc/testsuite/g++.dg/cpp0x/pr80259.C.jj	2017-12-01 12:06:54.611405404 +0100
+++ gcc/testsuite/g++.dg/cpp0x/pr80259.C	2017-12-01 12:06:19.000000000 +0100
@@ -0,0 +1,13 @@
+// PR c++/80259
+// { dg-do compile { target c++11 } }
+
+void foo () {}	// { dg-message "previously defined here" }
+void bar ();
+
+struct A
+{
+  friend void foo () = delete;	// { dg-error "redefinition of" }
+  friend void bar () = delete;	// { dg-message "previously defined here" }
+};
+
+void bar () {}	// { dg-error "redefinition of" }

	Jakub