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P0849 auto(x): DECAY_COPY in the language #293

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wg21bot opened this issue Jan 30, 2019 · 13 comments
Open

P0849 auto(x): DECAY_COPY in the language #293

wg21bot opened this issue Jan 30, 2019 · 13 comments

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@wg21bot
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@wg21bot wg21bot commented Jan 30, 2019

P0849R0 auto(x): DECAY_COPY in the language (Zhihao Yuan)

@wg21bot wg21bot added this to the 2019-02 milestone Jan 30, 2019
@wg21bot wg21bot added EWG LEWG labels Jan 30, 2019
@jensmaurer
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@jensmaurer jensmaurer commented Jan 30, 2019

Marked as "backlog" on San Diego EWG-I wiki.

@jensmaurer jensmaurer added EWGI and removed EWG LEWG labels Jan 30, 2019
@jfbastien jfbastien added this to EWGIMonday in EWGIKonaFeb2019 Feb 15, 2019
@jfbastien jfbastien moved this from EWGIMonday to Schedule me in EWGIKonaFeb2019 Feb 16, 2019
@jfbastien jfbastien moved this from Schedule me to EWGIMonday in EWGIKonaFeb2019 Feb 16, 2019
@jfbastien jfbastien moved this from EWGIMonday to EWGITuesday in EWGIKonaFeb2019 Feb 16, 2019
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@jfbastien jfbastien commented Feb 23, 2019

Discussed in EWG-I in Kona, want to see again with updates.

@jfbastien jfbastien removed the EWG-I Kona label Feb 24, 2019
@jfbastien jfbastien modified the milestones: 2019-02, 2019-07 Feb 24, 2019
@jensmaurer jensmaurer removed this from the 2019-07 milestone Mar 21, 2019
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@wg21bot wg21bot commented Jun 23, 2019

P0849R1 auto(x): decay-copy in the language (Zhihao Yuan)

@wg21bot wg21bot added this to the 2019-07 milestone Jun 23, 2019
@jensmaurer jensmaurer added this to Tuesday in EWG-I in Cologne 2019 Jul 11, 2019
@jfbastien
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@jfbastien jfbastien commented Jul 18, 2019

EWGI in Cologne:
Continue spending committee time on this versus other proposals, given that time is limited?
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Forward to EWG with the additional discussions requested.
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@jfbastien jfbastien removed the EWGI label Jul 18, 2019
@jensmaurer jensmaurer removed this from the 2019-07 milestone Aug 23, 2019
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@wg21bot wg21bot commented Oct 15, 2019

P0849R2 auto(x): decay-copy in the language (Zhihao Yuan)

@wg21bot wg21bot added this to the 2019-11 milestone Oct 15, 2019
@jfbastien jfbastien added this to Would be nice to talk about in EWGBelfast2019 Oct 15, 2019
@jfbastien jfbastien added this to Unscheduled in EWG Prague Jan 22, 2020
@jensmaurer jensmaurer modified the milestones: 2019-11, 2020-02 Jan 22, 2020
@jfbastien jfbastien moved this from Unscheduled to Friday in EWG Prague Jan 23, 2020
@jfbastien jfbastien moved this from Friday to Tuesday in EWG Prague Jan 24, 2020
@jfbastien jfbastien moved this from Tuesday to Overflow in EWG Prague Feb 11, 2020
@jfbastien jfbastien moved this from Overflow to Thursday in EWG Prague Feb 12, 2020
@jfbastien
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@jfbastien jfbastien commented Feb 13, 2020

EWG Prague Thursday morning:

auto(expr) is a problem worth solving.

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decltype(auto) is a problem worth solving.

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We like the solution for auto(expr) as presented, have LWG review the updated paper to confirm what they would use, then send it back to us.

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@jfbastien jfbastien added needs-revision LWG and removed EWG labels Feb 13, 2020
@jensmaurer jensmaurer removed this from the 2020-02 milestone Feb 18, 2020
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@wg21bot wg21bot commented Mar 24, 2020

P0849R3 auto(x): decay-copy in the language (Zhihao Yuan)

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@wg21bot wg21bot commented Oct 21, 2020

P0849R4 auto(x): decay-copy in the language (Zhihao Yuan)

@jwakely
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@jwakely jwakely commented Oct 30, 2020

LWG reviewed Part 2 of the wording in our telecon. It was observed that some of the changes have semantic changes for the better (e.g. auto(t.begin()) is a no-op if t.begin() returns a prvalue, where decay-copy(t.begin()) forces temporary materialization and a copy). Some of the changes are not necessarily improvements (for some range adaptors we would need to say that auto(E) is materialized, because it's not implementable otherwise). In other cases it's semantically equivalent but the proposed new wording seems slightly clearer about those semantics.

LWG has no objection to EWG proceeding with this, but it would need another LWG review.

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@wg21bot wg21bot commented Nov 23, 2020

P0849R5 auto(x): decay-copy in the language (Zhihao Yuan)

@JeffGarland
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@JeffGarland JeffGarland commented Nov 24, 2020

@jfbastien have LWG review the updated paper to confirm what they would use, then send it back to us.

I believe this belongs back on EWG plate (also still target in paper) for formal approval after LWG confirms desire to use. Switching labels.

@JeffGarland JeffGarland added EWG and removed LWG lwg-prereview labels Nov 24, 2020
@jfbastien
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@jfbastien jfbastien commented Dec 8, 2020

The paper was discussed in an EWG telecon on December 3rd 2020.

Polls:

Instead of spelling it auto, spell it more explicitly for example prvalue_cast.

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We should hold P0849 for a while to consider whether instead of or in addition to P0849, C++ needs the capability to forward prvalue through functions in C++ (for example, as suggested in P0927 or P1221).

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We’d like to see the feedback items brought up today before forwarding P0849

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Forward P0849 to LEWG / LWG for feedback on the library parts. If they have no language feedback, forward the language part to CWG.

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We'll need to do electronic polling of this paper, and hope that the R6 update will come this month.

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@wg21bot wg21bot commented Dec 27, 2020

P0849R6 auto(x): decay-copy in the language (Zhihao Yuan)

@wg21bot wg21bot modified the milestones: 2020-telecon, 2021-telecon Dec 27, 2020
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