Make is_constructible public (#918)

include/fmt/core.h

@@ -208,14 +208,6 @@ FMT_CONSTEXPR typename std::make_unsigned<Int>::type to_unsigned(Int value) {
   return static_cast<typename std::make_unsigned<Int>::type>(value);
 }
 
-#if FMT_GCC_VERSION && FMT_GCC_VERSION < 405
-template <typename... T>
-struct is_constructible: std::false_type {};
-#else
-template <typename... T>
-struct is_constructible : std::is_constructible<T...> {};
-#endif
-
 /** A contiguous memory buffer with an optional growing ability. */
 template <typename T>
 class basic_buffer {
@@ -337,6 +329,14 @@ template <typename T>
 struct no_formatter_error : std::false_type {};
 }  // namespace internal
 
+#if FMT_GCC_VERSION && FMT_GCC_VERSION < 405
+template <typename... T>
+struct is_constructible: std::false_type {};
+#else
+template <typename... T>
+struct is_constructible : std::is_constructible<T...> {};
+#endif
+
 /**
   An implementation of ``std::basic_string_view`` for pre-C++17. It provides a
   subset of the API. ``fmt::basic_string_view`` is used for format strings even
@@ -725,7 +725,7 @@ inline typename std::enable_if<
 
 template <typename C, typename T, typename Char = typename C::char_type>
 inline typename std::enable_if<
-    internal::is_constructible<basic_string_view<Char>, T>::value &&
+    is_constructible<basic_string_view<Char>, T>::value &&
     !internal::is_string<T>::value,
     init<C, basic_string_view<Char>, string_type>>::type
   make_value(const T &val) { return basic_string_view<Char>(val); }
@@ -734,7 +734,7 @@ template <typename C, typename T, typename Char = typename C::char_type>
 inline typename std::enable_if<
     !convert_to_int<T, Char>::value && !std::is_same<T, Char>::value &&
     !std::is_convertible<T, basic_string_view<Char>>::value &&
-    !internal::is_constructible<basic_string_view<Char>, T>::value &&
+    !is_constructible<basic_string_view<Char>, T>::value &&
     !internal::is_string<T>::value,
     // Implicit conversion to std::string is not handled here because it's
     // unsafe: https://github.com/fmtlib/fmt/issues/729

test/core-test.cc

@@ -569,3 +569,43 @@ TEST(CoreTest, FormatForeignStrings) {
   EXPECT_EQ(fmt::format(QString(L"{}"), my_string<wchar_t>(L"42")), L"42");
   EXPECT_EQ(fmt::format(my_string<wchar_t>(L"{}"), QString(L"42")), L"42");
 }
+
+struct implicitly_convertible_to_string_view {
+  operator fmt::string_view() const { return "foo"; }
+};
+
+TEST(FormatterTest, FormatImplicitlyConvertibleToStringView) {
+  EXPECT_EQ("foo", fmt::format("{}", implicitly_convertible_to_string_view()));
+}
+
+// std::is_constructible is broken in MSVC until version 2015.
+#if FMT_USE_EXPLICIT && (!FMT_MSC_VER || FMT_MSC_VER >= 1900)
+struct explicitly_convertible_to_string_view {
+  explicit operator fmt::string_view() const { return "foo"; }
+};
+
+TEST(FormatterTest, FormatExplicitlyConvertibleToStringView) {
+  EXPECT_EQ("foo", fmt::format("{}", explicitly_convertible_to_string_view()));
+}
+
+struct explicitly_convertible_to_wstring_view {
+  explicit operator fmt::wstring_view() const { return L"foo"; }
+};
+
+TEST(FormatterTest, FormatExplicitlyConvertibleToWStringView) {
+  EXPECT_EQ(L"foo",
+            fmt::format(L"{}", explicitly_convertible_to_wstring_view()));
+}
+
+struct explicitly_convertible_to_string_like {
+  template <
+      typename String,
+      typename = typename std::enable_if<
+        std::is_constructible<String, const char*, std::size_t>::value>::type>
+  FMT_EXPLICIT operator String() const { return String("foo", 3u); }
+};
+
+TEST(FormatterTest, FormatExplicitlyConvertibleToStringLike) {
+  EXPECT_EQ("foo", fmt::format("{}", explicitly_convertible_to_string_like()));
+}
+#endif

test/format-test.cc

@@ -1549,45 +1549,6 @@ TEST(FormatterTest, FormatStdStringView) {
 }
 #endif
 
-struct implicitly_convertible_to_string_view {
-  operator fmt::string_view() const { return "foo"; }
-};
-
-TEST(FormatterTest, FormatImplicitlyConvertibleToStringView) {
-  EXPECT_EQ("foo", format("{}", implicitly_convertible_to_string_view()));
-}
-
-// std::is_constructible is broken in MSVC until version 2015.
-#if FMT_USE_EXPLICIT && (!FMT_MSC_VER || FMT_MSC_VER >= 1900)
-struct explicitly_convertible_to_string_view {
-  explicit operator fmt::string_view() const { return "foo"; }
-};
-
-TEST(FormatterTest, FormatExplicitlyConvertibleToStringView) {
-  EXPECT_EQ("foo", format("{}", explicitly_convertible_to_string_view()));
-}
-
-struct explicitly_convertible_to_wstring_view {
-  explicit operator fmt::wstring_view() const { return L"foo"; }
-};
-
-TEST(FormatterTest, FormatExplicitlyConvertibleToWStringView) {
-  EXPECT_EQ(L"foo", format(L"{}", explicitly_convertible_to_wstring_view()));
-}
-
-struct explicitly_convertible_to_string_like {
-  template <
-      typename String,
-      typename = typename std::enable_if<
-        std::is_constructible<String, const char*, std::size_t>::value>::type>
-  FMT_EXPLICIT operator String() const { return String("foo", 3u); }
-};
-
-TEST(FormatterTest, FormatExplicitlyConvertibleToStringLike) {
-  EXPECT_EQ("foo", format("{}", explicitly_convertible_to_string_like()));
-}
-#endif
-
 FMT_BEGIN_NAMESPACE
 template <>
 struct formatter<Date> {