Fix PR c++/68948 (wrong code generation due to invalid constructor call)

gcc/cp/ChangeLog:

	PR c++/68948
	* pt.c (tsubst_baselink): Diagnose an invalid constructor call
	if lookup_fnfields returns NULL_TREE and the name being looked
	up has the form A::A.

gcc/testsuite/ChangeLog:

	PR c++/68948
	* g++.dg/template/pr68948.C: New test.

From-SVN: r233176

gcc/cp/ChangeLog

+2016-02-05  Patrick Palka  <ppalka@gcc.gnu.org>
+
+	PR c++/68948
+	* pt.c (tsubst_baselink): Diagnose an invalid constructor call
+	if lookup_fnfields returns NULL_TREE and the name being looked
+	up has the form A::A.
+
 2016-02-04  Patrick Palka  <ppalka@gcc.gnu.org>
 
 	* constexpr.c (cxx_eval_binary_expression): Fold equality

gcc/cp/pt.c

@@ -13583,7 +13583,15 @@ tsubst_baselink (tree baselink, tree object_type,
       name = mangle_conv_op_name_for_type (optype);
     baselink = lookup_fnfields (qualifying_scope, name, /*protect=*/1);
     if (!baselink)
-      return error_mark_node;
+      {
+	if (constructor_name_p (name, qualifying_scope))
+	  {
+	    if (complain & tf_error)
+	      error ("cannot call constructor %<%T::%D%> directly",
+		     qualifying_scope, name);
+	  }
+	return error_mark_node;
+      }
 
     /* If lookup found a single function, mark it as used at this
        point.  (If it lookup found multiple functions the one selected

gcc/testsuite/ChangeLog

+2016-02-05  Patrick Palka  <ppalka@gcc.gnu.org>
+
+	PR c++/68948
+	* g++.dg/template/pr68948.C: New test.
+
 2016-02-05  Dominik Vogt  <vogt@linux.vnet.ibm.com>
 
 	* gcc.dg/tree-ssa/ssa-dom-cse-2.c: Remove -march=z13 for s390

gcc/testsuite/g++.dg/template/pr68948.C

+// PR c++/68948
+
+struct B { B (); B (int); };
+
+struct Time : B { };
+
+/* Here, A and B are unrelated types.  */
+
+template <typename>
+struct A
+{
+  void TestBody ()
+  {
+    B::B (); // { dg-error "cannot call constructor .B::B." }
+    B::B::B (); // { dg-error "cannot call constructor .B::B." }
+    B::B (0); // { dg-error "cannot call constructor .B::B." }
+  }
+};
+
+/* Here, C is (indirectly) derived from B.  */
+
+template <typename g>
+struct C : Time
+{
+  void TestBody ()
+  {
+    B::B (); // { dg-error "cannot call constructor .B::B." }
+    B::B::B (); // { dg-error "cannot call constructor .B::B." }
+    B::B (0); // { dg-error "cannot call constructor .B::B." }
+    Time::B (0);
+  }
+};
+
+int
+main (void)
+{
+  A<int> a;
+  C<int> c;
+  a.TestBody ();
+  c.TestBody ();
+}