gcc 4.8 interprets inaccessible as a hard error (instead of... not available)

include/fmt/ostream.h

@@ -129,17 +129,22 @@ template <typename T> struct streamed_view { const T& value; };
 
 // Formats an object of type T that has an overloaded ostream operator<<.
 template <typename Char>
-struct basic_ostream_formatter
-    : private formatter<basic_string_view<Char>, Char> {
-  using basic_ostream_formatter::formatter::parse;
+struct basic_ostream_formatter {
+private:
+  formatter<basic_string_view<Char>, Char> underlying_;
+
+public:
+  template <typename ParseContext>
+  FMT_CONSTEXPR auto parse(ParseContext& ctx) -> decltype(ctx.begin()) {
+    return underlying_.parse(ctx);
+  }
 
   template <typename T, typename OutputIt>
   auto format(const T& value, basic_format_context<OutputIt, Char>& ctx) const
       -> OutputIt {
     auto buffer = basic_memory_buffer<Char>();
     format_value(buffer, value, ctx.locale());
-    return formatter<basic_string_view<Char>, Char>::format(
-        {buffer.data(), buffer.size()}, ctx);
+    return underlying_.format({buffer.data(), buffer.size()}, ctx);
   }
 };