Fix formatting of exotic characters

include/fmt/core.h

@@ -771,7 +771,7 @@ FMT_MAKE_VALUE(uint_type, unsigned char, unsigned)
 template <typename C, typename Char,
           FMT_ENABLE_IF(std::is_same<typename C::char_type, Char>::value)>
 FMT_CONSTEXPR init<C, int, char_type> make_value(Char val) {
-  return val;
+  return {val};
 }
 
 template <typename C,

include/fmt/format.h

@@ -2025,7 +2025,7 @@ template <typename Char, typename Handler>
 FMT_CONSTEXPR const Char* parse_precision(const Char* begin, const Char* end,
                                           Handler&& handler) {
   ++begin;
-  auto c = begin != end ? *begin : 0;
+  auto c = begin != end ? *begin : Char();
   if ('0' <= c && c <= '9') {
     handler.on_precision(parse_nonnegative_int(begin, end, handler));
   } else if (c == '{') {
@@ -2763,8 +2763,9 @@ template <typename Range> class basic_writer {
     auto&& it = reserve(1);
     *it++ = value;
   }
-  void write(wchar_t value) {
-    static_assert(std::is_same<char_type, wchar_t>::value, "");
+
+  template <typename Char, FMT_ENABLE_IF(std::is_same<Char, char_type>::value)>
+  void write(Char value) {
     auto&& it = reserve(1);
     *it++ = value;
   }

test/format-test.cc

@@ -2492,3 +2492,21 @@ TEST(FormatTest, CharTraitsIsNotAmbiguous) {
   (void)lval;
 #endif
 }
+
+struct mychar {
+  int value;
+  mychar() = default;
+  mychar(char val) : value(val) {}
+  operator int() const { return value; }
+};
+
+FMT_BEGIN_NAMESPACE
+template <> struct is_char<mychar> : std::true_type {};
+FMT_END_NAMESPACE
+
+TEST(FormatTest, FormatCustomChar) {
+  const mychar format[] = {'{', '}', 0};
+  auto result = fmt::format(format, mychar('x'));
+  EXPECT_EQ(result.size(), 1);
+  EXPECT_EQ(result[0], mychar('x'));
+}