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

[Jakub Jelinek]

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  <ja...@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