is_trivially_move_assignable doesn't exist in libstdc++ 4.x

test/variant_valueless.cpp

@@ -14,6 +14,7 @@
 #include <stdexcept>
 
 using namespace boost::variant2;
+namespace v2d = boost::variant2::detail;
 
 #define STATIC_ASSERT(...) static_assert(__VA_ARGS__, #__VA_ARGS__)
 
@@ -34,7 +35,7 @@ STATIC_ASSERT( std::is_nothrow_default_constructible<X1>::value );
 STATIC_ASSERT( std::is_nothrow_copy_constructible<X1>::value );
 STATIC_ASSERT( std::is_nothrow_move_constructible<X1>::value );
 STATIC_ASSERT( std::is_trivially_destructible<X1>::value );
-STATIC_ASSERT( std::is_trivially_move_assignable<X1>::value );
+STATIC_ASSERT( v2d::is_trivially_move_assignable<X1>::value );
 STATIC_ASSERT( std::is_nothrow_constructible<X1, E1>::value );
 STATIC_ASSERT( !std::is_nothrow_constructible<X1, E1x>::value );
 
@@ -83,7 +84,7 @@ STATIC_ASSERT( !std::is_nothrow_default_constructible<X3>::value );
 STATIC_ASSERT( !std::is_nothrow_copy_constructible<X3>::value );
 STATIC_ASSERT( !std::is_nothrow_move_constructible<X3>::value );
 STATIC_ASSERT( std::is_trivially_destructible<X3>::value );
-STATIC_ASSERT( std::is_trivially_move_assignable<X3>::value );
+STATIC_ASSERT( v2d::is_trivially_move_assignable<X3>::value );
 STATIC_ASSERT( std::is_nothrow_constructible<X3, E3>::value );
 STATIC_ASSERT( !std::is_nothrow_constructible<X3, E3x>::value );