Simplify append_float_length

format.h

@@ -1493,8 +1493,14 @@ class BasicWriter {
   // Do not implement!
   void operator<<(typename internal::CharTraits<Char>::UnsupportedStrType);
 
+  // Appends floating-point length specifier to the format string.
+  // The second argument is only used for overload resolution.
+  void append_float_length(Char *&format_ptr, long double) {
+    *format_ptr++ = 'L';
+  }
+
   template<typename T>
-  Char* append_float_length(Char* format_ptr) { return format_ptr; }
+  void append_float_length(Char *&, T) {}
 
   friend class internal::ArgFormatter<Char>;
   friend class internal::PrintfFormatter<Char>;
@@ -1927,7 +1933,7 @@ void BasicWriter<Char>::write_double(
     *format_ptr++ = '*';
   }
 
-  format_ptr = append_float_length<T>(format_ptr);
+  append_float_length(format_ptr, value);
   *format_ptr++ = type;
   *format_ptr = '\0';
 
@@ -1981,16 +1987,6 @@ void BasicWriter<Char>::write_double(
   }
 }
 
-template <> template <> inline char* BasicWriter<char>::append_float_length<long double>( char* format_ptr) {
-    *format_ptr++ = 'L';
-    return format_ptr;
-}
-
-template <> template <> inline wchar_t* BasicWriter<wchar_t>::append_float_length<long double>( wchar_t* format_ptr) {
-    *format_ptr++ = 'L';
-    return format_ptr;
-}
-
 /**
   \rst
   This template provides operations for formatting and writing data into