Fix incorrect comment about std::auto_ptr

	* include/backward/auto_ptr.h (dauto_ptr): Correct comment about
	conversions from auto_ptr<Derived> rvalues to auto_ptr<Base>.
	* testsuite/20_util/auto_ptr/assign_neg.cc: Remove redundant dg-error
	directives that only match notes, not errors.

From-SVN: r241349

libstdc++-v3/ChangeLog

 2016-10-19  Jonathan Wakely  <jwakely@redhat.com>
 
+	* include/backward/auto_ptr.h (dauto_ptr): Correct comment about
+	conversions from auto_ptr<Derived> rvalues to auto_ptr<Base>.
+	* testsuite/20_util/auto_ptr/assign_neg.cc: Remove redundant dg-error
+	directives that only match notes, not errors.
+
 	* testsuite/experimental/memory/shared_ptr/cons/unique_ptr_ctor.cc:
 	Add tests for valid and invalid conversions.
 	* testsuite/experimental/memory/shared_ptr/cons/weak_ptr_ctor.cc:

libstdc++-v3/include/backward/auto_ptr.h

@@ -249,13 +249,17 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
       /** 
        *  @brief  Automatic conversions
        *
-       *  These operations convert an %auto_ptr into and from an auto_ptr_ref
-       *  automatically as needed.  This allows constructs such as
+       *  These operations are supposed to convert an %auto_ptr into and from
+       *  an auto_ptr_ref automatically as needed.  This would allow
+       *  constructs such as
        *  @code
        *    auto_ptr<Derived>  func_returning_auto_ptr(.....);
        *    ...
        *    auto_ptr<Base> ptr = func_returning_auto_ptr(.....);
        *  @endcode
+       *
+       *  But it doesn't work, and won't be fixed. For further details see
+       *  http://cplusplus.github.io/LWG/lwg-closed.html#463
        */
       auto_ptr(auto_ptr_ref<element_type> __ref) throw()
       : _M_ptr(__ref._M_ptr) { }

libstdc++-v3/testsuite/20_util/auto_ptr/assign_neg.cc

@@ -47,6 +47,3 @@ main()
   test01();
   return 0;
 }
-// { dg-error "::auto_ptr|no known conversion" "" { target *-*-* } 136 } 
-// { dg-error "note" "" { target *-*-* } 154 }
-// { dg-error "::auto_ptr|no known conversion" "" { target *-*-* } 264 }