[ 2021-01-16; Zhihao Yuan provides wording ]

Previous resolution [SUPERSEDED]:

This wording is relative to N4878.

1. Modify [specialized.construct] as indicated:

   template<class T, class... Args>
     constexpr T* construct_at(T* location, Args&&... args);
   
   namespace ranges {
     template<class T, class... Args>
       constexpr T* construct_at(T* location, Args&&... args);
   }
   

   -1- Constraints: The expression ::new (declval<void*>()) T(declval<Args>()...) is well-formed when treated as an unevaluated operand.

   -2- Effects: Equivalent to:

   returnauto ptr = ::new (voidify(*location)) T(std::forward<Args>(args)...);
   if constexpr (is_array_v<T>)
     return launder(location);
   else
     return ptr;