Don't use deprecated API.

format.h

@@ -1611,7 +1611,7 @@ template <typename Char, typename T>
 void format(BasicWriter<Char> &w, const FormatSpec &spec, const T &value) {
   std::basic_ostringstream<Char> os;
   os << value;
-  w.Write(os.str(), spec);
+  w.write(os.str(), spec);
 }
 
 namespace internal {

test/format-test.cc

@@ -1324,7 +1324,7 @@ class Answer {};
 
 template <typename Char>
 void format(BasicWriter<Char> &w, const fmt::FormatSpec &spec, Answer) {
-  w.Write("42", spec);
+  w.write("42", spec);
 }
 
 TEST(FormatterTest, CustomFormat) {

test/util-test.cc

@@ -206,8 +206,8 @@ void CheckThrowError(int error_code, FormatErrorMessage format,
 TEST(UtilTest, FormatSystemErrorMessage) {
   fmt::Writer message;
   fmt::internal::FormatSystemErrorMessage(message, EDOM, "test");
-  EXPECT_EQ(str(fmt::Format("test: {}")
-          << GetSystemErrorMessage(EDOM)), fmt::str(message));
+  EXPECT_EQ(str(fmt::format("test: {}",
+          GetSystemErrorMessage(EDOM))), fmt::str(message));
 }
 
 TEST(UtilTest, SystemErrorSink) {
@@ -240,7 +240,7 @@ TEST(UtilTest, FormatWinErrorMessage) {
   fmt::Writer actual_message;
   fmt::internal::FormatWinErrorMessage(
       actual_message, ERROR_FILE_EXISTS, "test");
-  EXPECT_EQ(str(fmt::Format("test: {}") << fmt::str(utf8_message)),
+  EXPECT_EQ(str(fmt::format("test: {}", fmt::str(utf8_message))),
       fmt::str(actual_message));
 }