Made vec_deque::Drain, hash_map::Drain, and hash_set::Drain covariant #35354
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Thanks for the pull request, and welcome! The Rust team is excited to review your changes, and you should hear from @brson (or someone else) soon. If any changes to this PR are deemed necessary, please add them as extra commits. This ensures that the reviewer can see what has changed since they last reviewed the code. Due to the way GitHub handles out-of-date commits, this should also make it reasonably obvious what issues have or haven't been addressed. Large or tricky changes may require several passes of review and changes. Please see the contribution instructions for more information. |
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I don't understand the issues here enough to review. There's a bunch of new unsafe code though, which is suspicious... cc @rust-lang/libs |
brson
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r? @sfackler maybe? |
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cc @apasel422 |
| @@ -897,8 +898,9 @@ unsafe impl<K: Send, V: Send> Send for IntoIter<K, V> {} | |||
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| /// Iterator over the entries in a table, clearing the table. | |||
| pub struct Drain<'a, K: 'a, V: 'a> { | |||
| table: &'a mut RawTable<K, V>, | |||
| table: Shared<RawTable<K, V>>, | |||
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This seems curious because today it's implemented in seeming "safe" code, but that didn't get us the right variance by default?
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&mut T is invariant in T. But we're reading (K, V) out of the table, not writing to it, so covariance should be safe. This isn't conveyed by &mut RawTable<K, V> alone, because the compiler has to assume that such a reference could be written to.
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@bors: r+ Discussed during triage yesterday, decision was to merge! |
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📌 Commit bf592ce has been approved by |
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⌛ Testing commit bf592ce with merge 514d4ce... |
Made vec_deque::Drain, hash_map::Drain, and hash_set::Drain covariant Fixed the rest of the Drain iterators.
#30642
Fixed the rest of the Drain iterators.