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[unord.hash] Redundant wording LWG 3512 #4437

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JohelEGP opened this issue Dec 28, 2020 · 3 comments · Fixed by #4438
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[unord.hash] Redundant wording LWG 3512 #4437

JohelEGP opened this issue Dec 28, 2020 · 3 comments · Fixed by #4438
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lwg Issue must be reviewed by LWG. not-editorial Issue is not deemed editorial; the editorial issue is kept open for tracking.

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@JohelEGP
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[unord.hash]p5.4 ends with "shall not throw an exception unless hash<Key> is a program-defined specialization that depends on at least one program-defined type."

"that depends on at least one program-defined type" is redundant given [namespace.std]p2: "Unless explicitly prohibited, a program may add a template specialization for any standard library class template to namespace std provided that (a) the added declaration depends on at least one program-defined type ..."
@JohelEGP JohelEGP mentioned this issue Dec 28, 2020
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@jwakely
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jwakely commented Dec 28, 2020

I agree those words are redundant, but is that wording even true? If the hash function is hash<optional<T>> then it's not a program-defined specialization, but it can throw if hash<T> can throw.

Rather than fixing the redundancy as an editorial issue, we need to fix the falsehood as an LWG issue.

@JohelEGP
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You're right. Fortunately, the redundant part comes after the falsehood part.

@Dani-Hub
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A corresponding LWG issue exists now: LWG 3512

@jensmaurer jensmaurer changed the title [unord.hash] Redundant wording [unord.hash] Redundant wording LWG 3512 Jan 21, 2021
@jensmaurer jensmaurer added lwg Issue must be reviewed by LWG. not-editorial Issue is not deemed editorial; the editorial issue is kept open for tracking. labels Jan 21, 2021
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[unord.hash] Remove redundant wording JohelEGP/draft
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@Dani-Hub @jwakely @JohelEGP @jensmaurer