Cleanup base API

test/format-test.cc

@@ -2022,8 +2022,8 @@ TEST(format_test, named_arg_udl) {
 TEST(format_test, enum) { EXPECT_EQ(fmt::format("{}", foo), "0"); }
 
 TEST(format_test, formatter_not_specialized) {
-  static_assert(!fmt::has_formatter<fmt::formatter<test_enum>,
-                                    fmt::format_context>::value,
+  static_assert(!fmt::is_formattable<fmt::formatter<test_enum>,
+                                     fmt::format_context>::value,
                 "");
 }