Simplify a copying the fill from basic_specs

include/fmt/base.h

@@ -842,6 +842,12 @@ class basic_specs {
     for (size_t i = 0; i < size; ++i)
       fill_data_[i & 3] = static_cast<char>(s[i]);
   }
+
+  FMT_CONSTEXPR void set_fill(const basic_specs& specs) {
+    set_fill_size(specs.fill_size());
+    for (size_t i = 0; i < max_fill_size; ++i)
+      fill_data_[i] = specs.fill_data_[i];
+  }
 };
 
 // Format specifiers for built-in and string types.

include/fmt/format.h

@@ -3654,17 +3654,6 @@ void vformat_to(buffer<Char>& buf, basic_string_view<Char> fmt,
   parse_format_string(
       fmt, format_handler<Char>{parse_context<Char>(fmt), {out, args, loc}});
 }
-
-template <typename Char>
-void basic_specs_copy_fill(basic_specs& dst, const basic_specs& src) {
-  if (src.fill_size() == 1 && const_check(!std::is_same<Char, char>::value)) {
-    Char fill = src.fill_unit<Char>();
-    dst.set_fill(basic_string_view<Char>(&fill, 1));
-    return;
-  }
-  dst.set_fill(basic_string_view<char>(src.fill<char>(), src.fill_size()));
-}
-
 }  // namespace detail
 
 FMT_BEGIN_EXPORT
@@ -3971,7 +3960,7 @@ template <typename T, typename Char = char> struct nested_formatter {
     write(basic_appender<Char>(buf));
     auto specs = format_specs();
     specs.width = width_;
-    detail::basic_specs_copy_fill<Char>(specs, specs_);
+    specs.set_fill(specs_);
     specs.set_align(specs_.align());
     return detail::write<Char>(
         ctx.out(), basic_string_view<Char>(buf.data(), buf.size()), specs);

include/fmt/std.h

@@ -696,7 +696,7 @@ template <typename T, typename Char> struct formatter<std::complex<T>, Char> {
 
     auto outer_specs = format_specs();
     outer_specs.width = specs.width;
-    detail::basic_specs_copy_fill<Char>(outer_specs, specs);
+    outer_specs.set_fill(specs);
     outer_specs.set_align(specs.align());
 
     specs.width = 0;