Deprecate fmt::char8_t

include/fmt/core.h

@@ -315,6 +315,12 @@ FMT_CONSTEXPR typename std::make_unsigned<Int>::type to_unsigned(Int value) {
   FMT_ASSERT(value >= 0, "negative value");
   return static_cast<typename std::make_unsigned<Int>::type>(value);
 }
+
+#ifdef __cpp_char8_t
+using char8_type = char8_t;
+#else
+enum char8_type : unsigned char {};
+#endif
 }  // namespace internal
 
 template <typename... Ts>
@@ -415,15 +421,15 @@ using string_view = basic_string_view<char>;
 using wstring_view = basic_string_view<wchar_t>;
 
 #ifndef __cpp_char8_t
-// A UTF-8 code unit type.
+// char8_t is deprecated; use char instead.
-enum char8_t : unsigned char {};
+using char8_t FMT_DEPRECATED_ALIAS = internal::char8_type;
 #endif
 
 /** Specifies if ``T`` is a character type. Can be specialized by users. */
 template <typename T> struct is_char : std::false_type {};
 template <> struct is_char<char> : std::true_type {};
 template <> struct is_char<wchar_t> : std::true_type {};
-template <> struct is_char<char8_t> : std::true_type {};
+template <> struct is_char<internal::char8_type> : std::true_type {};
 template <> struct is_char<char16_t> : std::true_type {};
 template <> struct is_char<char32_t> : std::true_type {};
 

include/fmt/format.h

@@ -482,7 +482,7 @@ inline size_t count_code_points(basic_string_view<char> s) {
   return num_code_points;
 }
 
-inline size_t count_code_points(basic_string_view<char8_t> s) {
+inline size_t count_code_points(basic_string_view<char8_type> s) {
   return count_code_points(basic_string_view<char>(
       reinterpret_cast<const char*>(s.data()), s.size()));
 }
@@ -494,8 +494,8 @@ inline size_t code_point_index(basic_string_view<Char> s, size_t n) {
 }
 
 // Calculates the index of the nth code point in a UTF-8 string.
-inline size_t code_point_index(basic_string_view<char8_t> s, size_t n) {
+inline size_t code_point_index(basic_string_view<char8_type> s, size_t n) {
-  const char8_t* data = s.data();
+  const char8_type* data = s.data();
   size_t num_code_points = 0;
   for (size_t i = 0, size = s.size(); i != size; ++i) {
     if ((data[i] & 0xc0) != 0x80 && ++num_code_points > n) {
@@ -505,13 +505,13 @@ inline size_t code_point_index(basic_string_view<char8_t> s, size_t n) {
   return s.size();
 }
 
-inline char8_t to_char8_t(char c) { return static_cast<char8_t>(c); }
+inline char8_type to_char8_t(char c) { return static_cast<char8_type>(c); }
 
 template <typename InputIt, typename OutChar>
 using needs_conversion = bool_constant<
     std::is_same<typename std::iterator_traits<InputIt>::value_type,
                  char>::value &&
-    std::is_same<OutChar, char8_t>::value>;
+    std::is_same<OutChar, char8_type>::value>;
 
 template <typename OutChar, typename InputIt, typename OutputIt,
           FMT_ENABLE_IF(!needs_conversion<InputIt, OutChar>::value)>
@@ -555,20 +555,22 @@ class buffer_range : public internal::output_range<
       : internal::output_range<iterator, T>(std::back_inserter(buf)) {}
 };
 
-class FMT_DEPRECATED u8string_view : public basic_string_view<char8_t> {
+class FMT_DEPRECATED u8string_view
+    : public basic_string_view<internal::char8_type> {
  public:
   u8string_view(const char* s)
-      : basic_string_view<char8_t>(reinterpret_cast<const char8_t*>(s)) {}
+      : basic_string_view<internal::char8_type>(
+            reinterpret_cast<const internal::char8_type*>(s)) {}
   u8string_view(const char* s, size_t count) FMT_NOEXCEPT
-      : basic_string_view<char8_t>(reinterpret_cast<const char8_t*>(s), count) {
+      : basic_string_view<internal::char8_type>(
-  }
+            reinterpret_cast<const internal::char8_type*>(s), count) {}
 };
 
 #if FMT_USE_USER_DEFINED_LITERALS
 inline namespace literals {
-FMT_DEPRECATED inline basic_string_view<char8_t> operator"" _u(const char* s,
+FMT_DEPRECATED inline basic_string_view<internal::char8_type> operator"" _u(
-                                                               std::size_t n) {
+    const char* s, std::size_t n) {
-  return {reinterpret_cast<const char8_t*>(s), n};
+  return {reinterpret_cast<const internal::char8_type*>(s), n};
 }
 }  // namespace literals
 #endif

test/format-impl-test.cc

@@ -10,12 +10,11 @@
 #include "test-assert.h"
 
 // Include format.cc instead of format.h to test implementation.
-#include "../src/format.cc"
-#include "fmt/printf.h"
-
 #include <algorithm>
 #include <cstring>
 
+#include "../src/format.cc"
+#include "fmt/printf.h"
 #include "gmock.h"
 #include "gtest-extra.h"
 #include "util.h"
@@ -430,8 +429,10 @@ TEST(FormatTest, CountCodePoints) {
 #ifndef __cpp_char8_t
   using fmt::char8_t;
 #endif
-  EXPECT_EQ(4, fmt::internal::count_code_points(
+  EXPECT_EQ(
-    fmt::basic_string_view<char8_t>(reinterpret_cast<const char8_t*>("ёжик"))));
+      4, fmt::internal::count_code_points(
+             fmt::basic_string_view<fmt::internal::char8_type>(
+                 reinterpret_cast<const fmt::internal::char8_type*>("ёжик"))));
 }
 
 // Tests fmt::internal::count_digits for integer type Int.

test/format-test.cc

@@ -2504,25 +2504,6 @@ TEST(FormatTest, FmtStringInTemplate) {
 
 #endif  // FMT_USE_CONSTEXPR
 
-// C++20 feature test, since r346892 Clang considers char8_t a fundamental
-// type in this mode. If this is the case __cpp_char8_t will be defined.
-#ifndef __cpp_char8_t
-// Locally provide type char8_t defined in format.h
-using fmt::char8_t;
-#endif
-
-// Convert 'char8_t' character sequences to 'char' sequences
-// Otherwise GTest will insist on inserting 'char8_t' NTBS into a 'char' stream,
-// but basic_ostream<char>::operator<< overloads taking 'char8_t' arguments
-// are defined as deleted by P1423.
-// Handling individual 'char8_t's is done inline.
-std::string from_u8str(const std::basic_string<char8_t>& str) {
-  return std::string(str.begin(), str.end());
-}
-std::string from_u8str(const fmt::basic_string_view<char8_t>& str) {
-  return std::string(str.begin(), str.end());
-}
-
 TEST(FormatTest, EmphasisNonHeaderOnly) {
   // Ensure this compiles even if FMT_HEADER_ONLY is not defined.
   EXPECT_EQ(fmt::format(fmt::emphasis::bold, "bold error"),
@@ -2561,10 +2542,18 @@ TEST(FormatTest, FormatCustomChar) {
   EXPECT_EQ(result[0], mychar('x'));
 }
 
+// Convert a char8_t string to std::string. Otherwise GTest will insist on
+// inserting `char8_t` NTBS into a `char` stream which is disabled by P1423.
+template <typename S> std::string from_u8str(const S& str) {
+  return std::string(str.begin(), str.end());
+}
+
 TEST(FormatTest, FormatUTF8Precision) {
-  using str_type = std::basic_string<char8_t>;
+  using str_type = std::basic_string<fmt::internal::char8_type>;
-  str_type format(reinterpret_cast<const char8_t*>(u8"{:.4}"));
+  str_type format(
-  str_type str(reinterpret_cast<const char8_t*>(u8"caf\u00e9s"));  // cafés
+      reinterpret_cast<const fmt::internal::char8_type*>(u8"{:.4}"));
+  str_type str(reinterpret_cast<const fmt::internal::char8_type*>(
+      u8"caf\u00e9s"));  // cafés
   auto result = fmt::format(format, str);
   EXPECT_EQ(fmt::internal::count_code_points(result), 4);
   EXPECT_EQ(result.size(), 5);