VS 2019 support

Author: gershnik

lib/inc/sys_string/config.h

@@ -111,6 +111,12 @@
     #define SYS_STRING_LIBCPP_AT_LEAST(v) 0
 #endif
 
+#if defined(__GLIBCXX__)
+    #define SYS_STRING_GLIBCXX_AT_LEAST(v) (_GLIBCXX_RELEASE >= (v))
+#else
+    #define SYS_STRING_GLIBCXX_AT_LEAST(v) 0
+#endif
+
 #if __cpp_lib_endian < 201907
     #error Your standard library does not support std::endian
 #endif
@@ -128,10 +134,21 @@
 #endif
 
 
-#if __cpp_lib_format >= 201907L || (SYS_STRING_LIBCPP_AT_LEAST(170000) && __has_include(<format>))
+#if __cpp_lib_format >= 202207L \
+    || (SYS_STRING_LIBCPP_AT_LEAST(170000) && __has_include(<format>)) \
+    || (SYS_STRING_GLIBCXX_AT_LEAST(13) && __has_include(<format>))
 
     #define SYS_STRING_SUPPORTS_STD_FORMAT 1
 
 #endif
 
+// True iff the compiler reliably matches trailing requires-clauses on
+// out-of-line definitions of constrained member templates.
+#if (defined(__apple_build_version__) && __apple_build_version__ < 14030022) \
+    || (defined(_MSC_VER) && _MSC_VER < 1930)
+    #define SYS_STRING_HAS_TRAILING_REQUIRES_BUG 1
+#else
+    #define SYS_STRING_HAS_TRAILING_REQUIRES_BUG 0
+#endif
+
 #endif

lib/inc/sys_string/impl/misc.h

@@ -269,7 +269,7 @@ namespace sysstr
     template<class Storage>
     template<class Search, class OutIt>
     auto sys_string_t<Storage>::split(OutIt dest, Search search) const -> OutIt
-    #if !(defined(__apple_build_version__) && __apple_build_version__ < 14030022)
+    #if !SYS_STRING_HAS_TRAILING_REQUIRES_BUG
     requires(std::output_iterator<OutIt, sys_string_t> &&
              std::is_invocable_v<Search, typename sys_string_t::utf32_access::iterator, std::default_sentinel_t>)
     #endif
@@ -281,7 +281,7 @@ namespace sysstr
     template<class Storage>
     template<sys_string_or_char<Storage> StringOrChar, class OutIt>
     auto sys_string_t<Storage>::split(OutIt dest, const StringOrChar & sep, size_t max_split) const -> OutIt
-    #if !(defined(__apple_build_version__) && __apple_build_version__ < 14030022)
+    #if !SYS_STRING_HAS_TRAILING_REQUIRES_BUG
     requires(std::output_iterator<OutIt, sys_string_t>)
     #endif
     {

lib/inc/sys_string/sys_string.h

@@ -345,15 +345,15 @@ namespace sysstr
 
         template<class Search, class OutIt>
         auto split(OutIt dest, Search search) const -> OutIt
-        #if !(defined(__apple_build_version__) && __apple_build_version__ < 14030022)
+        #if !SYS_STRING_HAS_TRAILING_REQUIRES_BUG
         requires(std::output_iterator<OutIt, sys_string_t> &&
                  std::is_invocable_v<Search, typename sys_string_t::utf32_access::iterator, std::default_sentinel_t>)
         #endif         
         ;
 
         template<sys_string_or_char<Storage> StringOrChar, class OutIt>
         auto split(OutIt dest, const StringOrChar & sep, size_t max_split = std::numeric_limits<size_t>::max()) const -> OutIt
-        #if !(defined(__apple_build_version__) && __apple_build_version__ < 14030022)
+        #if !SYS_STRING_HAS_TRAILING_REQUIRES_BUG
         requires(std::output_iterator<OutIt, sys_string_t>)
         #endif
         ;