Fix ostream support in sprintf (#1631)

test/core-test.cc

@@ -210,7 +210,8 @@ TEST(ArgTest, FormatArgs) {
 }
 
 struct custom_context {
-  typedef char char_type;
+  using char_type = char;
+  using parse_context_type = fmt::format_parse_context;
 
   template <typename T> struct formatter_type {
     template <typename ParseContext>

test/format-test.cc

@@ -2259,8 +2259,9 @@ struct test_parse_context {
 };
 
 struct test_context {
-  typedef char char_type;
-  typedef fmt::basic_format_arg<test_context> format_arg;
+  using char_type = char;
+  using format_arg = fmt::basic_format_arg<test_context>;
+  using parse_context_type = fmt::format_parse_context;
 
   template <typename T> struct formatter_type {
     typedef fmt::formatter<T, char_type> type;

test/printf-test.cc

@@ -502,9 +502,7 @@ TEST(PrintfTest, PrintfError) {
 TEST(PrintfTest, WideString) { EXPECT_EQ(L"abc", fmt::sprintf(L"%s", L"abc")); }
 
 TEST(PrintfTest, PrintfCustom) {
-  // The test is disabled for now because it requires decoupling
-  // fallback_formatter::format from format_context.
-  //EXPECT_EQ("abc", test_sprintf("%s", TestString("abc")));
+  EXPECT_EQ("abc", test_sprintf("%s", TestString("abc")));
 }
 
 TEST(PrintfTest, OStream) {