Proposed resolution:

This wording is relative to N5032.

1. Modify [exec.as.awaitable] as indicated:

   -4- Let `rcvr` be an rvalue expression of type awaitable-receiver, let `crcvr` be a const lvalue that refers to `rcvr`, let `vs` be a pack of subexpressions, and let `err` be an expression of type `Err`. Let MAKE-NOEXCEPT(expr) for some subexpression `expr` be expression-equivalent to [&] noexcept -> decltype(auto) { return (expr); }(). Then:

   1. (4.1) — If constructible_from<result-type, decltype((vs))...> is satisfied, the expression `set_value(rcvr, vs...)` is equivalent to:

      try {
        rcvr.result-ptr->template emplace<1>(vs...);
      } catch(...) {
        rcvr.result-ptr->template emplace<2>(current_exception());
      }
      MAKE-NOEXCEPT(rcvr.continuation.resume());
      

      Otherwise, `set_value(rcvr, vs...)` is ill-formed.

   2. (4.2) — The expression `set_error(rcvr, err)` is equivalent to:

      try {
        rcvr.result-ptr->template emplace<2>(AS-EXCEPT-PTR(err));
      } catch(...) {
        rcvr.result-ptr->template emplace<2>(current_exception());
      }
      MAKE-NOEXCEPT(rcvr.continuation.resume());
      

   3. (4.3) — The expression `set_stopped(rcvr)` is equivalent to:

      MAKE-NOEXCEPT(static_cast<coroutine_handle<>>(rcvr.continuation.promise().unhandled_stopped()).resume());
      

   4. (4.4) — For any expression `tag` whose type satisfies forwarding-query and for any pack of subexpressions `as`, `get_env(crcvr).query(tag, as...)` is expression-equivalent to:

      tag(get_env(as_const(MAKE-NOEXCEPT(crcvr.continuation.promise()))), as...)
      

[ Croydon 2026-03-28; Status changed: Immediate → WP. ]

[ Croydon 2026-03-27; Status changed: New → Immediate. ]

[ 2026-03-27; Tim adds wording following LWG discussion ]

[ 2024-08-21; Reflector poll ]

Set priority to 1 after reflector poll.

`promise()` can probably be Throws: Nothing (along with a bunch of other coroutine_handle members), but `resume()` certainly can throw. Also AS-EXCEPT-PTR can throw for the `error_code` case (that might be worth a separate issue though).

The specification of awaitable-receiver in [exec.as.awaitable]/p4 as of N4988 is not taking into consideration the fact that the resume() and promise() member functions on coroutine_handle<P> are not marked noexcept. awaitable-receiver's member functions must all be noexcept, but they are specified as being "equivalent to" statement that call resume() and promise() outside of try/catch blocks.