C++ PATCH for c++/61490 - qualified-id in friend function definition

[Marek Polacek]

[class.friend]/6 says that when we define a function in a friend declaration,
the function name must be unqualified.  But we never made sure that's so.

For good measure, I'm also improving the location of the related diagnostic.

Bootstrapped/regtested on x86_64-linux, ok for trunk?

2019-06-17  Marek Polacek  <pola...@redhat.com>

        PR c++/61490 - qualified-id in friend function definition.
        * decl.c (grokdeclarator): Diagnose qualified-id in friend function
        definition.  Improve location for diagnostics of friend functions.

        * g++.dg/diagnostic/friend2.C: New test.
        * g++.dg/diagnostic/friend3.C: New test.

diff --git gcc/cp/decl.c gcc/cp/decl.c
index 0a3ef452536..efc49137cdc 100644
--- gcc/cp/decl.c
+++ gcc/cp/decl.c
@@ -11605,13 +11605,29 @@ grokdeclarator (const cp_declarator *declarator,
                    friendp = 0;
                  }
                if (decl_context == NORMAL)
-                 error ("friend declaration not in class definition");
+                 error_at (declarator->id_loc,
+                           "friend declaration not in class definition");
                if (current_function_decl && funcdef_flag)
                  {
-                   error ("cannot define friend function %qs in a local "
-                          "class definition", name);
+                   error_at (declarator->id_loc,
+                             "cannot define friend function %qs in a local "
+                             "class definition", name);
                    friendp = 0;
                  }
+               /* [class.friend]/6: A function can be defined in a friend
+                  declaration if the function name is unqualified.  */
+               if (funcdef_flag && in_namespace)
+                 {
+                   if (in_namespace == global_namespace)
+                     error_at (declarator->id_loc,
+                               "friend function definition %qs cannot have "
+                               "a name qualified with %<::%>", name);
+                   else
+                     error_at (declarator->id_loc,
+                               "friend function definition %qs cannot have "
+                               "a name qualified with %<%D::%>", name,
+                               in_namespace);
+                 }
              }
            else if (ctype && sfk == sfk_conversion)
              {
diff --git gcc/testsuite/g++.dg/diagnostic/friend2.C 
gcc/testsuite/g++.dg/diagnostic/friend2.C
new file mode 100644
index 00000000000..4f4ada8bc16
--- /dev/null
+++ gcc/testsuite/g++.dg/diagnostic/friend2.C
@@ -0,0 +1,10 @@
+// PR c++/61490
+// { dg-do compile }
+
+namespace N { void f (); }
+void f2 ();
+
+struct A {
+  friend void N::f () { } // { dg-error "15:friend function definition 'f' 
cannot have a name qualified with 'N::'" }
+  friend void ::f2 () { } // { dg-error "15:friend function definition 'f2' 
cannot have a name qualified with '::'" }
+};
diff --git gcc/testsuite/g++.dg/diagnostic/friend3.C 
gcc/testsuite/g++.dg/diagnostic/friend3.C
new file mode 100644
index 00000000000..574d7caa5fb
--- /dev/null
+++ gcc/testsuite/g++.dg/diagnostic/friend3.C
@@ -0,0 +1,9 @@
+// { dg-do compile }
+
+void
+fn ()
+{
+  struct S {
+    friend void bar () { } // { dg-error "17:cannot define friend function 
'bar' in a local class definition" }
+  };
+}