Implement some trivial size_hints for various iterators #49201
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This also implements ExactSizeIterator where applicable. Addresses most of the Iterator traits mentioned in rust-lang#23708.
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r? @estebank (rust_highfive has picked a reviewer for you, use r? to override) |
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LGTM, @rust-lang/libs anything I might be overlooking? |
src/libcore/char.rs
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| #[inline] | ||
| fn size_hint(&self) -> (usize, Option<usize>) { | ||
| self.0.size_hint() |
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This look incorrect. This iterator can yield fewer chars than it has input u8s. See std::str::Chars::size_hint.
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Ah, right you are. I saw self.0.next().map(...) in the next() implementation and assumed that meant a 1:1 correspondence.
src/libcore/iter/traits.rs
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| @@ -901,6 +901,10 @@ impl<I, T, E> Iterator for ResultShunt<I, E> | |||
| None => None, | |||
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| fn size_hint(&self) -> (usize, Option<usize>) { | |||
| self.iter.size_hint() | |||
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This looks incorrect since this iterator can yield fewer items than self.iter. Also this particular iterator is private and as far as can tell its size_hint is never used.
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Yes, this should instead be:
let (_, upper) = self.iter.size_hint();
(0, upper)
And I guess it's never used? I didn't really look; figuring out if it's used is harder than implementing it just-in-case, and the code around it could change.
I can remove it if you like.
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I think it’s not used but this implementation is small enough that it’s probably fine to add it just in case it becomes used later.
src/libcore/option.rs
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| #[inline] | ||
| fn size_hint(&self) -> (usize, Option<usize>) { | ||
| self.iter.size_hint() |
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This looks incorrect since this iterator can yield fewer items than self.iter. See std::iter::Filter::size_hint.
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Oops, forgot to commit this file. I'll commit and push it tomorrow.
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r? @SimonSapin |
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It looks like (Please comment after pushing, I sometimes get email notifications for new commits but not always. I haven’t figured out in what cases.) |
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Pushed my code for |
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Thanks! @bors: r+ |
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📌 Commit 5057e3c has been approved by |
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Implement some trivial size_hints for various iterators This also implements ExactSizeIterator where applicable. Addresses most of the Iterator traits mentioned in #23708. I intend to do more, but I don't want to make the PR too large.
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☀️ Test successful - status-appveyor, status-travis |
This also implements ExactSizeIterator where applicable.
Addresses most of the Iterator traits mentioned in #23708.
I intend to do more, but I don't want to make the PR too large.