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[func.wrap.ref.class, func.wrap.ref.deduct] Inconsistent parameter #6362

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JohelEGP opened this issue Jun 28, 2023 · 5 comments · Fixed by #6398
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[func.wrap.ref.class, func.wrap.ref.deduct] Inconsistent parameter #6362

JohelEGP opened this issue Jun 28, 2023 · 5 comments · Fixed by #6398

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@JohelEGP
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In the class synopsis:

  template<auto f>
    function_ref(nontype_t<f>, auto) -> function_ref<see below>;

The detailed specifications uses a forwarding parameter.
That's consistent with the actual constructors,
as it doesn't require copy on the caller side when deducing.

    function_ref(nontype_t<f>, auto&&) -> function_ref<@\seebelow@>;

In the deduction guide's detailed specifications:

template<auto f, class T>
  function_ref(nontype_t<f>, T&&) -> function_ref<see below>;

The second parameter in the class synopsis is actually auto.
That requires a copy, as opposed to T&&.
So I can't solve this editorially here,
but it can be done in the class synopsis.

To be consistent with my suggestion on the class synopsis:

template<auto f>
  function_ref(nontype_t<f>, auto&&) -> function_ref<@\seebelow@>;

Originally: #6357 (comment), #6357 (comment).
@JohelEGP JohelEGP mentioned this issue Jun 28, 2023
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@frederick-vs-ja
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frederick-vs-ja commented Jun 29, 2023 •
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Presumably the second auto shouldn't be used here, see CWG2697.

@JohelEGP
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Thank you.
For now, I suggested #6357 (comment).
If that's not editorially accepted, an LWG issue might be needed.

@tkoeppe
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tkoeppe commented Jul 21, 2023

Could you please make a separate PR for this, after the motions?

@JohelEGP
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JohelEGP commented Jul 21, 2023 •
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Yes.
Remaining motions: https://github.com/cplusplus/draft/issues?q=is%3Aissue+is%3Aopen+Motion+in%3Atitle.
Commit to be rebased on main afterwards: 34305cc.

@JohelEGP JohelEGP mentioned this issue Jul 22, 2023
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@JohelEGP
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Opened #6398.

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[func.wrap.ref.class] change deduction guide to match its detailed specifications JohelEGP/draft
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@tkoeppe @JohelEGP @frederick-vs-ja