Simplify arg_formatter

test/custom-formatter-test.cc

@@ -18,10 +18,9 @@
 // A custom argument formatter that doesn't print `-` for floating-point values
 // rounded to 0.
 class custom_arg_formatter
-    : public fmt::arg_formatter<fmt::buffer_range<char>> {
+    : public fmt::arg_formatter<fmt::format_context::iterator, char> {
  public:
-  using range = fmt::buffer_range<char>;
-  typedef fmt::arg_formatter<range> base;
+  using base = fmt::arg_formatter<fmt::format_context::iterator, char>;
 
   custom_arg_formatter(fmt::format_context& ctx,
                        fmt::format_parse_context* parse_ctx,
@@ -39,8 +38,10 @@ class custom_arg_formatter
 
 std::string custom_vformat(fmt::string_view format_str, fmt::format_args args) {
   fmt::memory_buffer buffer;
+  fmt::internal::buffer<char>& base = buffer;
   // Pass custom argument formatter as a template arg to vwrite.
-  fmt::vformat_to<custom_arg_formatter>(buffer, format_str, args);
+  fmt::vformat_to<custom_arg_formatter>(std::back_inserter(base), format_str,
+                                        args);
   return std::string(buffer.data(), buffer.size());
 }
 

test/format-test.cc

@@ -1847,7 +1847,9 @@ class mock_arg_formatter
 
 static void custom_vformat(fmt::string_view format_str, fmt::format_args args) {
   fmt::memory_buffer buffer;
-  fmt::vformat_to<mock_arg_formatter>(buffer, format_str, args);
+  fmt::internal::buffer<char>& base = buffer;
+  fmt::vformat_to<mock_arg_formatter>(std::back_inserter(base), format_str,
+                                      args);
 }
 
 template <typename... Args>

test/ostream-test.cc

@@ -64,12 +64,13 @@ TEST(OStreamTest, Enum) {
   EXPECT_EQ(L"0", fmt::format(L"{}", unstreamable_enum()));
 }
 
-using range = fmt::buffer_range<char>;
-
-struct test_arg_formatter : fmt::arg_formatter<range> {
+struct test_arg_formatter
+    : fmt::arg_formatter<fmt::buffer_range<char>::iterator, char> {
   fmt::format_parse_context parse_ctx;
   test_arg_formatter(fmt::format_context& ctx, fmt::format_specs& s)
-      : fmt::arg_formatter<range>(ctx, &parse_ctx, &s), parse_ctx("") {}
+      : fmt::arg_formatter<fmt::buffer_range<char>::iterator, char>(
+            ctx, &parse_ctx, &s),
+        parse_ctx("") {}
 };
 
 TEST(OStreamTest, CustomArg) {