P2098 `std::is_specialization_of`

[brycelelbach]

Prague 2020-02 LEWGI Minutes

D2098R0 std::is_specialization_of: Direction Review

Chair: Fabio Fracassi

Champion: Walter Brown

Minute Taker: Ben Craig

Start Review: 2020-02-15 09:37

Examples: Yes, in paper.

Implementation experience: Add examples to paper.

Prior art: Yes, in paper.

• Add a reference to P1985, the language feature proposal that would allow the more general form in the future.

Wording: Yes, in paper.

If we get features to extend this to be more general in the future (e.g. P1985), can we do it with the std::is_specialization_of name, or would an extension have to be a new type trait under a new name? Answer: It sounds like we would be able to extend std::is_specialization_of without issues.

Start Polling: 09:46

POLL: We like this paper, send it forward to LEWG.

Strongly For	Weakly For	Neutral	Weakly Against	Strongly Against
10	7	0	0

Attendance: 19

# of Authors: 2

Author Position: SF

That has unanimous consent.

End: 9:55

CONSENSUS: LEWGI sends D2098R0 (std::is_specialization_of) to LEWG for C++23.

[wg21bot]

P2098R0 Proposing std::is_specialization_of (Walter E Brown, Bob Steagall)

[wg21bot]

P2098R1 Proposing std::is_specialization_of (Walter E Brown, Bob Steagall)

[brycelelbach]

P2098R1: std::is_specialization_of

2020-05-04 Library Evolution Telecon Minutes

Chair: Nevin Liber

Champion: Walter Brown

Minute Taker: Ben Craig

Start Review: 2020-05-04 08:05 Pacific

Magic compiler builtin vs library-only.

Options:

• Push this forward now, extend later with a language extension.
• Design this as if we have the language extension.
• Don't do this now.

Start Polling: 08:51

POLL: We want is_specialization_of (in some form) if it is fully generalized.

Strongly Favor	Weakly Favor	Neutral	Weakly Against	Strongly Against
9	8	7	2	1

Attendance: 33

# of Authors: 1

Author Position: SF

That has consensus.

POLL: We want is_specialization_of even if it has the limitations discussed
in the paper.

Strongly Favor	Weakly Favor	Neutral	Weakly Against	Strongly Against
2	5	7	10	2

Attendance: 33

# of Authors: 1

Author Position: SF

That has no consensus.

End: 09:07

CONSENSUS: We will not pursue P2098R0 (std::is_specialization_of) at this time; we'd like to see a solution to this problem, but it requires language evolution too.