1 files changed, 16 insertions, 9 deletions

diff --git a/include/fmt/ranges.h b/include/fmt/ranges.h
index c0b51aee..3638fffb 100644
--- a/include/fmt/ranges.h
+++ b/include/fmt/ranges.h
@@ -183,7 +183,7 @@ template <size_t N> using make_index_sequence = std::make_index_sequence<N>;
 template <typename T, T... N> struct integer_sequence {
   using value_type = T;
 
-  static FMT_CONSTEXPR size_t size() { return sizeof...(N); }
+  static FMT_CONSTEXPR auto size() -> size_t { return sizeof...(N); }
 };
 
 template <size_t... N> using index_sequence = integer_sequence<size_t, N...>;
@@ -207,15 +207,15 @@ class is_tuple_formattable_ {
 };
 template <typename T, typename C> class is_tuple_formattable_<T, C, true> {
   template <std::size_t... Is>
-  static std::true_type check2(index_sequence<Is...>,
-                               integer_sequence<bool, (Is == Is)...>);
-  static std::false_type check2(...);
+  static auto check2(index_sequence<Is...>,
+                     integer_sequence<bool, (Is == Is)...>) -> std::true_type;
+  static auto check2(...) -> std::false_type;
   template <std::size_t... Is>
-  static decltype(check2(
+  static auto check(index_sequence<Is...>) -> decltype(check2(
       index_sequence<Is...>{},
-      integer_sequence<
-          bool, (is_formattable<typename std::tuple_element<Is, T>::type,
-                                C>::value)...>{})) check(index_sequence<Is...>);
+      integer_sequence<bool,
+                       (is_formattable<typename std::tuple_element<Is, T>::type,
+                                       C>::value)...>{}));
 
  public:
   static constexpr const bool value =
@@ -417,6 +417,12 @@ struct is_formattable_delayed
 #endif
 }  // namespace detail
 
+template <typename...> struct conjunction : std::true_type {};
+template <typename P> struct conjunction<P> : P {};
+template <typename P1, typename... Pn>
+struct conjunction<P1, Pn...>
+    : conditional_t<bool(P1::value), conjunction<Pn...>, P1> {};
+
 template <typename T, typename Char, typename Enable = void>
 struct range_formatter;
 
@@ -482,7 +488,8 @@ struct range_formatter<
     for (; it != end; ++it) {
       if (i > 0) out = detail::copy_str<Char>(separator_, out);
       ctx.advance_to(out);
-      out = underlying_.format(mapper.map(*it), ctx);
+      auto&& item = *it;
+      out = underlying_.format(mapper.map(item), ctx);
       ++i;
     }
     out = detail::copy_str<Char>(closing_bracket_, out);