Add another workaround to std::variant for Clang bug 31852

	* include/std/variant (_VARIANT_RELATION_FUNCTION_TEMPLATE): Qualify
	__get calls to avoid ADL and avoid ambiguity due to Clang bug.

From-SVN: r259135

libstdc++-v3/ChangeLog

+2018-04-05  Jonathan Wakely  <jwakely@redhat.com>
+
+	* include/std/variant (_VARIANT_RELATION_FUNCTION_TEMPLATE): Qualify
+	__get calls to avoid ADL and avoid ambiguity due to Clang bug.
+
 2018-04-03  Jonathan Wakely  <jwakely@redhat.com>
 
 	PR libstdc++/85183
@@ -18,7 +23,7 @@
 	(less::__not_overloaded, greater_equal::__not_overloaded)
 	(less_equal::__not_overloaded): Fix ambiguous specializations.
 	* testsuite/20_util/function_objects/comparisons_pointer.cc: Add
-	tests for type with overlaoded operators.
+	tests for type with overloaded operators.
 
 2018-03-22  Rainer Orth  <ro@CeBiTec.Uni-Bielefeld.DE>
 

libstdc++-v3/include/std/variant

@@ -272,8 +272,8 @@ namespace __variant
     constexpr bool \
     __erased_##__NAME(const _Variant& __lhs, const _Variant& __rhs) \
     { \
-      return __get<_Np>(std::forward<_Variant>(__lhs)) \
-	  __OP __get<_Np>(std::forward<_Variant>(__rhs)); \
+      return __variant::__get<_Np>(std::forward<_Variant>(__lhs)) \
+	  __OP __variant::__get<_Np>(std::forward<_Variant>(__rhs)); \
     }
 
   _VARIANT_RELATION_FUNCTION_TEMPLATE(<, less)