Unbloat chrono

include/fmt/chrono.h

@@ -2279,7 +2279,7 @@ struct formatter<std::chrono::duration<Rep, Period>, Char> {
     // As a possible future optimization, we could avoid extra copying if width
     // is not specified.
     auto buf = basic_memory_buffer<Char>();
-    auto out = std::back_inserter(buf);
+    auto out = basic_appender<Char>(buf);
     detail::handle_dynamic_spec<detail::width_checker>(specs.width, width_ref_,
                                                        ctx);
     detail::handle_dynamic_spec<detail::precision_checker>(precision,
@@ -2388,7 +2388,7 @@ template <typename Char> struct formatter<std::tm, Char> {
                  const Duration* subsecs) const -> decltype(ctx.out()) {
     auto specs = specs_;
     auto buf = basic_memory_buffer<Char>();
-    auto out = std::back_inserter(buf);
+    auto out = basic_appender<Char>(buf);
     detail::handle_dynamic_spec<detail::width_checker>(specs.width, width_ref_,
                                                        ctx);
 

include/fmt/format.h

@@ -1314,10 +1314,10 @@ FMT_CONSTEXPR20 auto format_decimal(Char* out, UInt value, int size)
   return {begin + n, end};
 }
 
-template <typename Char, typename UInt, typename Iterator,
-          FMT_ENABLE_IF(!std::is_pointer<remove_cvref_t<Iterator>>::value)>
-FMT_CONSTEXPR inline auto format_decimal(Iterator out, UInt value, int size)
-    -> format_decimal_result<Iterator> {
+template <typename Char, typename UInt, typename OutputIt,
+          FMT_ENABLE_IF(is_back_insert_iterator<OutputIt>::value)>
+FMT_CONSTEXPR inline auto format_decimal(OutputIt out, UInt value, int size)
+    -> format_decimal_result<OutputIt> {
   // Buffer is large enough to hold all digits (digits10 + 1).
   Char buffer[digits10<UInt>() + 1] = {};
   auto end = format_decimal(buffer, value, size).end;