From b98e8301d5812a4322d29519257ac50c1d9441db Mon Sep 17 00:00:00 2001
From: XZiar <czktc2007@gmail.com>
Date: Fri, 26 Oct 2018 15:55:03 -0700
Subject: [PATCH] add non-char support for compile-time format check

---
 include/fmt/core.h   |  8 +++++---
 include/fmt/format.h | 10 ++++++----
 test/format-test.cc  |  4 ++++
 3 files changed, 15 insertions(+), 7 deletions(-)

diff --git a/include/fmt/core.h b/include/fmt/core.h
index 676e7f7d..ca06f8c7 100644
--- a/include/fmt/core.h
+++ b/include/fmt/core.h
@@ -472,9 +472,11 @@ struct compile_string {};
 template <typename S>
 struct is_compile_string : std::is_base_of<compile_string, S> {};
 
-template <typename S>
-inline typename std::enable_if<is_compile_string<S>::value, string_view>::type
-  to_string_view(const S &s) { return {s.data(), s.size() - 1}; }
+template <typename S, typename Enable = std::enable_if<is_compile_string<S>::value>>
+inline auto to_string_view(const S &s) -> basic_string_view<typename S::Char> { 
+  typedef typename S::Char Char;
+  return basic_string_view<Char>{s.data(), s.size() - 1}; 
+}
 
 template <typename Context>
 class basic_format_arg;
diff --git a/include/fmt/format.h b/include/fmt/format.h
index 76ceee4b..1689b176 100644
--- a/include/fmt/format.h
+++ b/include/fmt/format.h
@@ -2243,9 +2243,10 @@ FMT_CONSTEXPR bool check_format_string(
 template <typename... Args, typename String>
 typename std::enable_if<is_compile_string<String>::value>::type
     check_format_string(String format_str) {
+  typedef typename String::Char Char;
   FMT_CONSTEXPR_DECL bool invalid_format =
-      internal::check_format_string<char, internal::error_handler, Args...>(
-        string_view(format_str.data(), format_str.size()));
+      internal::check_format_string<Char, internal::error_handler, Args...>(
+        basic_string_view<Char>(format_str.data(), format_str.size()));
   (void)invalid_format;
 }
 
@@ -3597,9 +3598,10 @@ FMT_END_NAMESPACE
 #define FMT_STRING(s) [] { \
     typedef typename std::decay<decltype(s)>::type pointer; \
     struct S : fmt::compile_string { \
+      typedef typename std::remove_cv<std::remove_pointer<pointer>::type>::type Char;\
       static FMT_CONSTEXPR pointer data() { return s; } \
-      static FMT_CONSTEXPR size_t size() { return sizeof(s); } \
-      explicit operator fmt::string_view() const { return s; } \
+      static FMT_CONSTEXPR size_t size() { return sizeof(s) / sizeof(Char); } \
+      explicit operator fmt::basic_string_view<Char>() const { return s; } \
     }; \
     return S{}; \
   }()
diff --git a/test/format-test.cc b/test/format-test.cc
index d6bbd19c..697a2ad2 100644
--- a/test/format-test.cc
+++ b/test/format-test.cc
@@ -1859,6 +1859,7 @@ TEST(FormatTest, UdlTemplate) {
   EXPECT_EQ("foo", "foo"_format());
   EXPECT_EQ("        42", "{0:10}"_format(42));
   EXPECT_EQ("42", fmt::format(FMT_STRING("{}"), 42));
+  EXPECT_EQ(L"42", fmt::format(FMT_STRING(L"{}"), 42));
 }
 #endif // FMT_USE_USER_DEFINED_LITERALS
 
@@ -2378,6 +2379,9 @@ TEST(FormatTest, VFormatTo) {
   std::wstring w;
   fmt::vformat_to(std::back_inserter(w), L"{}", wargs);
   EXPECT_EQ(L"42", w);
+  w.clear();
+  fmt::vformat_to(std::back_inserter(w), FMT_STRING(L"{}"), args);
+  EXPECT_EQ("42", w);
 }
 
 #endif  // FMT_USE_CONSTEXPR