re PR c++/56208 (Some classic sfinae cases fail to work due to access problems)

	PR c++/56208
	* pt.c (fn_type_unification): Discard any access checks from
	substituting explicit args.

From-SVN: r195779

gcc/cp/ChangeLog

+2013-02-05  Jason Merrill  <jason@redhat.com>
+
+	PR c++/56208
+	* pt.c (fn_type_unification): Discard any access checks from
+	substituting explicit args.
+
 2013-01-31  Jason Merrill  <jason@redhat.com>
 
 	PR c++/56162

gcc/cp/pt.c

@@ -14989,6 +14989,12 @@ fn_type_unification (tree fn,
       if (fntype == error_mark_node)
 	goto fail;
 
+      /* Throw away these access checks; we'll see them again in
+	 instantiate_template and they might have the wrong
+	 access path at this point.  */
+      pop_deferring_access_checks ();
+      push_deferring_access_checks (dk_deferred);
+
       /* Place the explicitly specified arguments in TARGS.  */
       for (i = NUM_TMPL_ARGS (explicit_targs); i--;)
 	TREE_VEC_ELT (targs, i) = TREE_VEC_ELT (explicit_targs, i);

gcc/testsuite/g++.dg/cpp0x/sfinae43.C

+// PR c++/56208
+// { dg-options -std=c++11 }
+
+struct ostream {
+  ostream& operator<<(int);
+};
+
+struct sfinae_base {
+
+  typedef char one;
+  typedef char (&two)[2];
+
+  template<class T>
+  static T make();
+
+  template<unsigned> struct ok { typedef int type; };
+
+  template<class U, class T>
+  static one test(decltype((make<U>() << make<T>()), 0));
+
+  template<class, class>
+  static two test(...);
+};
+
+template<class T>
+struct is_printable : private sfinae_base
+{
+  enum { value = sizeof(test<ostream&, T>(0)) == sizeof(one) };
+};
+
+typedef int ok[is_printable<int>::value ? 1 : -1];