Proposed resolution:

This wording is relative to ISO/IEC 14882:2020(E).

1. Modify [coroutine.handle.hash] as indicated:

   template<class P> struct hash<coroutine_handle<P>>;
   

   -1- The specialization is enabled ([unord.hash]) in a hosted implementation.

[ Brno 2026-06-12; Status changed: New → Resolved. ]

Resolved by P1642 for C++23 and later. LWG has no objection to the proposed wording for C++20.

[ 2025-11-11; Jonathan adds wording for C++20. ]

This wording would resolve the defect for C++20, but the issue should be closed as Resolved in C++23.

[ 2022-01-30; Reflector poll ]

Set priority to 3 after reflector poll. Would be resolved by P1642 for C++23, but it's still a defect in C++20.

The <coroutine> header is required for freestanding implementations, but it defines a specialization of std::hash, which is not required for freestanding implementations.

Presumably we should make the std::hash specialization conditionally present.