Put std::monostate in C++26 and above

Author: AmrDeveloper

libcxx/include/utility

@@ -267,7 +267,6 @@ template <class T>
 #  if _LIBCPP_STD_VER >= 17
 #    include <__utility/as_const.h>
 #    include <__utility/in_place.h>
-#    include <__variant/monostate.h>
 #  endif
 
 #  if _LIBCPP_STD_VER >= 20
@@ -280,6 +279,10 @@ template <class T>
 #    include <__utility/unreachable.h>
 #  endif
 
+#  if _LIBCPP_STD_VER >= 26
+#    include <__variant/monostate.h>
+#  endif
+
 #  include <version>
 
 // standard-mandated includes

libcxx/test/libcxx/transitive_includes/cxx17.csv

@@ -640,7 +640,6 @@ experimental/utility compare
 experimental/utility cstddef
 experimental/utility cstdint
 experimental/utility cstdlib
-experimental/utility cstring
 experimental/utility initializer_list
 experimental/utility iosfwd
 experimental/utility limits
@@ -2390,7 +2389,6 @@ tuple compare
 tuple cstddef
 tuple cstdint
 tuple cstdlib
-tuple cstring
 tuple exception
 tuple initializer_list
 tuple iosfwd
@@ -2407,7 +2405,6 @@ typeindex compare
 typeindex cstddef
 typeindex cstdint
 typeindex cstdlib
-typeindex cstring
 typeindex initializer_list
 typeindex iosfwd
 typeindex limits
@@ -2504,7 +2501,6 @@ utility compare
 utility cstddef
 utility cstdint
 utility cstdlib
-utility cstring
 utility initializer_list
 utility iosfwd
 utility limits

libcxx/test/libcxx/transitive_includes/cxx20.csv

@@ -636,7 +636,6 @@ experimental/utility compare
 experimental/utility cstddef
 experimental/utility cstdint
 experimental/utility cstdlib
-experimental/utility cstring
 experimental/utility initializer_list
 experimental/utility iosfwd
 experimental/utility limits
@@ -2418,7 +2417,6 @@ tuple compare
 tuple cstddef
 tuple cstdint
 tuple cstdlib
-tuple cstring
 tuple exception
 tuple initializer_list
 tuple iosfwd
@@ -2435,7 +2433,6 @@ typeindex compare
 typeindex cstddef
 typeindex cstdint
 typeindex cstdlib
-typeindex cstring
 typeindex initializer_list
 typeindex iosfwd
 typeindex limits
@@ -2532,7 +2529,6 @@ utility compare
 utility cstddef
 utility cstdint
 utility cstdlib
-utility cstring
 utility initializer_list
 utility iosfwd
 utility limits

libcxx/test/libcxx/transitive_includes/cxx23.csv

@@ -301,7 +301,6 @@ experimental/type_traits type_traits
 experimental/type_traits version
 experimental/utility compare
 experimental/utility cstdint
-experimental/utility cstring
 experimental/utility initializer_list
 experimental/utility limits
 experimental/utility utility
@@ -1117,7 +1116,6 @@ unordered_set tuple
 unordered_set version
 utility compare
 utility cstdint
-utility cstring
 utility initializer_list
 utility limits
 utility version