Add noexcept to std::integral_constant members

	* include/std/type_traits (integral_constant): Make member functions
	noexcept (LWG 2346).
	* include/std/utility (integer_sequence): Likewise.

From-SVN: r255312

libstdc++-v3/ChangeLog

+2017-12-01  Jonathan Wakely  <jwakely@redhat.com>
+
+	* include/std/type_traits (integral_constant): Make member functions
+	noexcept (LWG 2346).
+	* include/std/utility (integer_sequence): Likewise.
+
 2017-11-30  Jonathan Wakely  <jwakely@redhat.com>
 
 	PR libstdc++/65927

libstdc++-v3/include/std/type_traits

@@ -71,12 +71,12 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
       static constexpr _Tp                  value = __v;
       typedef _Tp                           value_type;
       typedef integral_constant<_Tp, __v>   type;
-      constexpr operator value_type() const { return value; }
+      constexpr operator value_type() const noexcept { return value; }
 #if __cplusplus > 201103L
 
 #define __cpp_lib_integral_constant_callable 201304
 
-      constexpr value_type operator()() const { return value; }
+      constexpr value_type operator()() const noexcept { return value; }
 #endif
     };
 

libstdc++-v3/include/std/utility

@@ -321,7 +321,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
     struct integer_sequence
     {
       typedef _Tp value_type;
-      static constexpr size_t size() { return sizeof...(_Idx); }
+      static constexpr size_t size() noexcept { return sizeof...(_Idx); }
     };
 
   /// Alias template make_integer_sequence