added a proposed resolution for issue 4347

[dietmarkuehl]

No description provided.

[Copilot]

Pull request overview

This PR adds a proposed resolution for issue 4347, which involves restructuring the stop token management in C++ execution's task class template. The resolution moves the stop_source_type and stop_token_type members from the promise_type class to the state class, and introduces a new exposition-only function get-stop-token() to manage stop token initialization more appropriately.

Changes:

• Adds an optional<stop_source_type> member and get-stop-token() function to the task::state class
• Modifies the start() method specification and adds the new get-stop-token() method specification in [task.state]
• Removes token and source members from promise_type in [task.promise]
• Updates get_env() specification to use STATE(*this).get-stop-token() instead of token

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[dietmarkuehl]

OK. I try to phrase it differently. I don’ really have a Returns: clause but the last paragraph does look somewhat like it.

The logic (for type erasing the stop token type) is:

if constexpr (<receiver’s stop token type matches>)
    return <receiver’s stop token>;
else {
    if (_source_.initialized)
        initialize _source_;
    return _source_->get_token();
}

The source shouldn’t exist if the type from the receiver matches.