remove conditional `is_convertible_*` structs for wide chars

include/spdlog/common.h

@@ -130,30 +130,12 @@ struct is_convertible_to_basic_format_string
 #ifdef SPDLOG_WCHAR_TO_UTF8_SUPPORT
 #    ifndef _WIN32
 #        error SPDLOG_WCHAR_TO_UTF8_SUPPORT only supported on windows
-#    else
-template<typename T>
-struct is_convertible_to_wstring_view : std::is_convertible<T, wstring_view_t>
-{};
-
-template<class T>
-using is_convertible_to_wformat_string = is_convertible_to_basic_format_string<T, wchar_t>;
 #    endif // _WIN32
-#else
-template<typename>
-struct is_convertible_to_wstring_view : std::false_type
-{};
-template<class>
-struct is_convertible_to_wformat_string : std::false_type
-{};
 #endif     // SPDLOG_WCHAR_TO_UTF8_SUPPORT
 
 template<class T>
-struct is_convertible_to_any_string_view
-    : std::integral_constant<bool, std::is_convertible<T, string_view_t>::value || is_convertible_to_wstring_view<T>::value>
-{};
-template<class T>
-struct is_convertible_to_any_format_string
-    : std::integral_constant<bool, is_convertible_to_basic_format_string<T, char>::value || is_convertible_to_wformat_string<T>::value>
+struct is_convertible_to_any_format_string : std::integral_constant<bool, is_convertible_to_basic_format_string<T, char>::value ||
+                                                                              is_convertible_to_basic_format_string<T, wchar_t>::value>
 {};
 
 #if defined(SPDLOG_NO_ATOMIC_LEVELS)

include/spdlog/logger.h

@@ -102,10 +102,8 @@ public:
         log(loc, lvl, string_view_t{msg});
     }
 
-    // T cannot be statically converted to neither string_view, nor wstring_view and nor format string
-    template<class T,
-        typename std::enable_if<
-            !is_convertible_to_any_string_view<const T &>::value && !is_convertible_to_any_format_string<const T &>::value, int>::type = 0>
+    // T cannot be statically converted to format string (including string_view)
+    template<class T, typename std::enable_if<!is_convertible_to_any_format_string<const T &>::value, int>::type = 0>
     void log(source_loc loc, level::level_enum lvl, const T &msg)
     {
         log(loc, lvl, "{}", msg);