More cleanup

include/fmt/core.h

@@ -1228,8 +1228,6 @@ struct is_contiguous<internal::buffer<Char>> : std::true_type {};
 
 namespace internal {
 
-// Workaround for a SFINAE issue in gcc < 9:
-// https://stackoverflow.com/q/56436995/471164
 template <typename OutputIt>
 struct is_contiguous_back_insert_iterator : std::false_type {};
 template <typename Container>

include/fmt/format.h

@@ -37,6 +37,8 @@
 #include <memory>
 #include <stdexcept>
 
+#include "core.h"
+
 #ifdef __clang__
 #  define FMT_CLANG_VERSION (__clang_major__ * 100 + __clang_minor__)
 #else
@@ -57,8 +59,6 @@
 #  define FMT_CUDA_VERSION 0
 #endif
 
-#include "core.h"
-
 #if FMT_GCC_VERSION >= 406 || FMT_CLANG_VERSION
 #  pragma GCC diagnostic push
 
@@ -2270,10 +2270,7 @@ void handle_dynamic_spec(Spec& value, arg_ref<typename Context::char_type> ref,
 
 /** The default argument formatter. */
 template <typename Range>
-class arg_formatter
-    : public internal::function<
-          typename internal::arg_formatter_base<Range>::iterator>,
-      public internal::arg_formatter_base<Range> {
+class arg_formatter : public internal::arg_formatter_base<Range> {
  private:
   typedef typename Range::value_type char_type;
   typedef internal::arg_formatter_base<Range> base;

include/fmt/printf.h

@@ -204,10 +204,7 @@ template <typename OutputIt, typename Char> class basic_printf_context;
   \endrst
  */
 template <typename Range>
-class printf_arg_formatter
-    : public internal::function<
-          typename internal::arg_formatter_base<Range>::iterator>,
-      public internal::arg_formatter_base<Range> {
+class printf_arg_formatter : public internal::arg_formatter_base<Range> {
  public:
   typedef decltype(std::declval<Range>().begin()) iterator;