Workaround for libc++: std::vector<bool>::reference has an overloaded…

… operator&.

Signed-off-by: Vladislav Shchapov <vladislav@shchapov.ru>

include/fmt/core.h

@@ -1283,7 +1283,14 @@ template <typename Context> class value {
 
   template <typename T> FMT_CONSTEXPR FMT_INLINE value(T& val) {
     using value_type = remove_const_t<T>;
+#if defined(_LIBCPP_VERSION)
+    // Workaround for formatter<std::vector<bool>::reference, Char>.
+    // libc++ std::vector<bool>::reference has an overloaded operator&.
+    // std::addressof is non-constexpr before C++17.
+    custom.value = const_cast<value_type*>(__builtin_addressof(val));
+#else
     custom.value = const_cast<value_type*>(&val);
+#endif
     // Get the formatter type through the context to allow different contexts
     // have different extension points, e.g. `formatter<T>` for `format` and
     // `printf_formatter<T>` for `printf`.