Tracking issue for Iterator::copied

[sugar700]

This is a tracking issue for Iterator::copied.

Added in #56534. Feature gate: #![feature(iter_copied)].

Related feature: copied in #57126.

[SimonSapin]

@Centril, do you feel your comment in #57126 (comment) is still an objection to the state of this feature, given the response in #57126 (comment)?

[Centril]

@SimonSapin So ultimately, #57970 was closed meaning that we are comfortable with the specialization. If that specialization is always in place then Copied is a redundant type (and the impls that come with it are also redundant). However, keeping the cost and the Copied type also has less of a risk attached to it so there's a trade-off here. I don't know what the right choice is, but those are the facts as I see them.

[sugar700]

@hellow554 Fixed :).

[sugar700]

For reference, .map(|&x| x) pattern is quite common according to https://codesearch.aelve.com/rust/search?query=%5C.%5Cs*map%5Cs*%5C(%5Cs*%5C%7C%5Cs*(%3F%3A%26%5Cs*%5Cw%2B%5Cs*%5C%7C%5Cs*%5C%7B%3F%5Cs*%5Cw%2B%7C%5Cw%2B%5Cs*%5C%7C%5Cs*%5C%7B%3F%5Cs*%5C*%5Cs*%5Cw%2B)%5Cs*%5C%7D%3F%5Cs*%5C)&insensitive=off&space=off&precise=off&sources=on

This includes both Iterators and Options, because a regex match cannot separate those.

[Manishearth]

@Centril Is there anything blocking stabilization here? We'd like to suggest this in Clippy, see rust-lang/rust-clippy#3958

(The crux is that .copied() is clearer than .map(|&x| x), but .cloned() gives off the wrong impression)

[Centril]

@Manishearth That's not my call... =D

Picking random libs member... @sfackler is there anything blocking stabilization here?

[sfackler]

Doesn't seem like it.

@rfcbot fcp merge

[rfcbot]

Team member @sfackler has proposed to merge this. The next step is review by the rest of the tagged team members:

• @Amanieu
• @Kimundi
• @SimonSapin
• @alexcrichton
• @dtolnay
• @sfackler
• @withoutboats

No concerns currently listed.

Once a majority of reviewers approve (and at most 2 approvals are outstanding), this will enter its final comment period. If you spot a major issue that hasn't been raised at any point in this process, please speak up!

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