From e724bbea162839133b26a44313673bf14751fe3b Mon Sep 17 00:00:00 2001
From: Victor Zverovich <viz@fb.com>
Date: Wed, 24 Aug 2022 10:00:12 -0700
Subject: [PATCH] Fix wchar_t corner cases

---
 include/fmt/core.h  |  2 +-
 include/fmt/xchar.h | 12 +++++-------
 test/xchar-test.cc  | 11 ++++++-----
 3 files changed, 12 insertions(+), 13 deletions(-)

diff --git a/include/fmt/core.h b/include/fmt/core.h
index 87444e03..b0eef0ae 100644
--- a/include/fmt/core.h
+++ b/include/fmt/core.h
@@ -3167,7 +3167,7 @@ template <typename Char, typename... Args> class basic_format_string {
 #if FMT_GCC_VERSION && FMT_GCC_VERSION < 409
 // Workaround broken conversion on older gcc.
 template <typename...> using format_string = string_view;
-inline auto runtime(string_view s) -> basic_string_view<char> { return s; }
+inline auto runtime(string_view s) -> string_view { return s; }
 #else
 template <typename... Args>
 using format_string = basic_format_string<char, type_identity_t<Args>...>;
diff --git a/include/fmt/xchar.h b/include/fmt/xchar.h
index faadf230..3b5bc15c 100644
--- a/include/fmt/xchar.h
+++ b/include/fmt/xchar.h
@@ -29,9 +29,11 @@ using wmemory_buffer = basic_memory_buffer<wchar_t>;
 #if FMT_GCC_VERSION && FMT_GCC_VERSION < 409
 // Workaround broken conversion on older gcc.
 template <typename... Args> using wformat_string = wstring_view;
+inline auto runtime(wstring_view s) -> wstring_view { return s; }
 #else
 template <typename... Args>
 using wformat_string = basic_format_string<wchar_t, type_identity_t<Args>...>;
+inline auto runtime(wstring_view s) -> basic_runtime<wchar_t> { return {{s}}; }
 #endif
 
 template <> struct is_char<wchar_t> : std::true_type {};
@@ -81,20 +83,16 @@ auto vformat(basic_string_view<Char> format_str,
   return to_string(buffer);
 }
 
-#if !FMT_GCC_VERSION || FMT_GCC_VERSION >= 409
-template <typename... Args>
-using wformat_string = basic_format_string<wchar_t, type_identity_t<Args>...>;
-#endif
-
 template <typename... T>
 auto format(wformat_string<T...> fmt, T&&... args) -> std::wstring {
-  return vformat(fmt, fmt::make_wformat_args(args...));
+  return vformat(fmt::wstring_view(fmt), fmt::make_wformat_args(args...));
 }
 
 // Pass char_t as a default template parameter instead of using
 // std::basic_string<char_t<S>> to reduce the symbol size.
 template <typename S, typename... Args, typename Char = char_t<S>,
-          FMT_ENABLE_IF(!std::is_same<Char, char>::value)>
+          FMT_ENABLE_IF(!std::is_same<Char, char>::value &&
+                        !std::is_same<Char, wchar_t>::value)>
 auto format(const S& format_str, Args&&... args) -> std::basic_string<Char> {
   return vformat(detail::to_string_view(format_str),
                  fmt::make_format_args<buffer_context<Char>>(args...));
diff --git a/test/xchar-test.cc b/test/xchar-test.cc
index b3da1f55..290042a6 100644
--- a/test/xchar-test.cc
+++ b/test/xchar-test.cc
@@ -84,7 +84,7 @@ TEST(xchar_test, format) {
   EXPECT_EQ(L"4.2", fmt::format(L"{}", 4.2));
   EXPECT_EQ(L"abc", fmt::format(L"{}", L"abc"));
   EXPECT_EQ(L"z", fmt::format(L"{}", L'z'));
-  EXPECT_THROW(fmt::format(L"{:*\x343E}", 42), fmt::format_error);
+  EXPECT_THROW(fmt::format(fmt::runtime(L"{:*\x343E}"), 42), fmt::format_error);
   EXPECT_EQ(L"true", fmt::format(L"{}", true));
   EXPECT_EQ(L"a", fmt::format(L"{0}", 'a'));
   EXPECT_EQ(L"a", fmt::format(L"{0}", L'a'));
@@ -98,8 +98,9 @@ TEST(xchar_test, is_formattable) {
 }
 
 TEST(xchar_test, compile_time_string) {
+  EXPECT_EQ(fmt::format(fmt::wformat_string<int>(L"{}"), 42), L"42");
 #if defined(FMT_USE_STRING_VIEW) && FMT_CPLUSPLUS >= 201703L
-  EXPECT_EQ(L"42", fmt::format(FMT_STRING(std::wstring_view(L"{}")), 42));
+  EXPECT_EQ(fmt::format(FMT_STRING(std::wstring_view(L"{}")), 42), L"42");
 #endif
 }
 
@@ -246,7 +247,7 @@ TEST(xchar_test, sign_not_truncated) {
   wchar_t format_str[] = {
       L'{', L':',
       '+' | static_cast<wchar_t>(1 << fmt::detail::num_bits<char>()), L'}', 0};
-  EXPECT_THROW(fmt::format(format_str, 42), fmt::format_error);
+  EXPECT_THROW(fmt::format(fmt::runtime(format_str), 42), fmt::format_error);
 }
 
 TEST(xchar_test, chrono) {
@@ -311,8 +312,8 @@ TEST(chrono_test_wchar, time_point) {
     auto sys_output = system_wcsftime(spec, &tm);
 
     auto fmt_spec = fmt::format(L"{{:{}}}", spec);
-    EXPECT_EQ(sys_output, fmt::format(fmt_spec, t1));
-    EXPECT_EQ(sys_output, fmt::format(fmt_spec, tm));
+    EXPECT_EQ(sys_output, fmt::format(fmt::runtime(fmt_spec), t1));
+    EXPECT_EQ(sys_output, fmt::format(fmt::runtime(fmt_spec), tm));
   }
 }