Proposed resolution:

This wording is relative to N4835.

1. Add

   #include <compare>
   

   to the following header synopses:

   1. [coroutine.syn]
   2. [system.error.syn]
   3. [utility.syn]
   4. [tuple.syn]
   5. [optional.syn]
   6. [variant.syn]
   7. [memory.syn]
   8. [type.index.synopsis]
   9. [string.syn]
   10. [string.view.synop]
   11. [array.syn]
   12. [deque.syn]
   13. [forward.list.syn]
   14. [list.syn]
   15. [vector.syn]
   16. [associative.map.syn]
   17. [associative.set.syn]
   18. [unord.map.syn]
   19. [unord.set.syn]
   20. [queue.syn]
   21. [stack.syn]
   22. [iterator.synopsis]
   23. [ranges.syn]
   24. [time.syn]
   25. [fs.filesystem.syn]
   26. [re.syn]
   27. [thread.syn]

[ 2019-11 Moved to Ready on Friday AM in Belfast ]

Addresses US 181

The spaceship operator<=> is typically not usable unless the library header <compare> is directly included by the user. Many standard library headers provide overloads for this operator. Worse, several standard classes have replaced their existing definition for comparison operators with a reliance on the spaceship operator, and existing code will break if the necessary header is not (transitively) included. In a manner similar to the mandated library headers transitively #include-ing <initializer_list> in C++11, these headers should mandate a transitive #include <compare>.

Proposed change:

Add:

#include <compare>

to the header synopsis for each of the following headers:

<array>
<chrono>
<coroutine>
<deque>
<forward_list>
<filesystem>
<iterator>
<list>
<map>
<memory>
<optional>
<queue>
<ranges>
<regex>
<set>
<stack>
<string>
<string_view>
<system_error>
<thread>
<tuple>
<type_index>
<unordered_map>
<unordered_set>
<utility>
<variant>
<vector>