PR c++/81236 - auto variable and auto function

	* pt.c (tsubst_baselink): Update the type of the BASELINK after
	mark_used.

From-SVN: r258547

gcc/cp/ChangeLog

 2018-03-14  Jason Merrill  <jason@redhat.com>
 
+	PR c++/81236 - auto variable and auto function
+	* pt.c (tsubst_baselink): Update the type of the BASELINK after
+	mark_used.
+
+2018-03-14  Jason Merrill  <jason@redhat.com>
+
 	PR c++/83916 - ICE with template template parameters.
 	* pt.c (convert_template_argument): Don't substitute into type of
 	non-type parameter if we don't have enough arg levels.

gcc/cp/pt.c

@@ -14700,9 +14700,16 @@ tsubst_baselink (tree baselink, tree object_type,
   /* If lookup found a single function, mark it as used at this point.
      (If lookup found multiple functions the one selected later by
      overload resolution will be marked as used at that point.)  */
-  if (!template_id_p && !really_overloaded_fn (fns)
-      && !mark_used (OVL_FIRST (fns), complain) && !(complain & tf_error))
-    return error_mark_node;
+  if (!template_id_p && !really_overloaded_fn (fns))
+    {
+      tree fn = OVL_FIRST (fns);
+      bool ok = mark_used (fn, complain);
+      if (!ok && !(complain & tf_error))
+	return error_mark_node;
+      if (ok && BASELINK_P (baselink))
+	/* We might have instantiated an auto function.  */
+	TREE_TYPE (baselink) = TREE_TYPE (fn);
+    }
 
   if (BASELINK_P (baselink))
     {

gcc/testsuite/g++.dg/cpp1y/auto-fn48.C

+// { dg-do compile { target c++14 } }
+
+template <class T> struct A
+{
+  static auto fn() { }
+  static void f()
+  {
+    auto x = fn;
+  }
+};
+
+int main()
+{
+  A<int>::f();
+}

gcc/testsuite/g++.dg/cpp1y/auto-fn49.C

+// CWG issue 2335
+// { dg-do compile { target c++14 } }
+
+template <class... Ts> struct partition_indices {
+  static auto compute_right () {}
+  static constexpr auto right = compute_right;
+};
+auto foo () -> partition_indices<>;
+void f() {
+  auto x = foo();
+  auto y = x.right;
+}