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cuviper opened this issue May 30, 2019 · 6 comments · Fixed by #61388
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hash_map::IterMut changed Send bounds with hashbrown #61357

cuviper opened this issue May 30, 2019 · 6 comments · Fixed by #61388
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A-collections Area: `std::collections` C-bug Category: This is a bug. regression-from-stable-to-beta Performance or correctness regression from stable to beta. T-libs-api Relevant to the library API team, which will review and decide on the PR/issue.

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@cuviper
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cuviper commented May 30, 2019

In 1.35, IterMut's Send requires K: Send, but in 1.36-beta it requires K: Sync. Both are auto-derived, so it must be a change in their internals. Obviously, hashbrown is quite different than the old implementation.

https://doc.rust-lang.org/1.35.0/std/collections/hash_map/struct.IterMut.html#impl-Send
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https://doc.rust-lang.org/beta/std/collections/hash_map/struct.IterMut.html#impl-Send
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Ditto for ValuesMut. I'm not sure if there's any real impact in this, but it should be considered, and perhaps audit for other similar changes.

cc @Amanieu, as discussed on IRC.
@cuviper cuviper added A-collections Area: `std::collections` C-bug Category: This is a bug. regression-from-stable-to-beta Performance or correctness regression from stable to beta. T-libs-api Relevant to the library API team, which will review and decide on the PR/issue. labels May 30, 2019
This was referenced May 30, 2019
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bors added a commit to rust-lang/hashbrown that referenced this issue May 30, 2019
@bors
Auto merge of #82 - Amanieu:itermut_send, r=Amanieu
9e18470 
Fix the bounds on K for the Send impl of IterMut

This makes the bounds match the ones of the previous `HashMap` implementation in libstd.

Fixes rust-lang/rust#61357
bors added a commit to rust-lang/hashbrown that referenced this issue May 30, 2019
@bors
Auto merge of #82 - Amanieu:itermut_send, r=Amanieu
a9ddbcf 
Fix the bounds on K for the Send impl of IterMut

This makes the bounds match the ones of the previous `HashMap` implementation in libstd.

cc rust-lang/rust#61357
@Amanieu
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Amanieu commented May 30, 2019

This is fixed in hashbrown 0.4.0.

@Amanieu Amanieu mentioned this issue May 31, 2019
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@aclonegeek
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@Amanieu Shouldn't ValuesMut be fixed as well?

@cuviper
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cuviper commented Jun 1, 2019

Since ValuesMut is actually based on IterMut, it derives the same constraints.
https://docs.rs/hashbrown/0.4.0/hashbrown/hash_map/struct.ValuesMut.html#synthetic-implementations

@aclonegeek
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@cuviper Ah, gotcha. Thanks! Sorry for the false alarm :).

Amanieu added a commit to Amanieu/rust that referenced this issue Jun 1, 2019
@Amanieu
Bump hashbrown to 0.4.0
a386a9e 
Fixes rust-lang#61357
bors added a commit that referenced this issue Jun 1, 2019
@bors
Auto merge of #61388 - Amanieu:hashbrown4, r=alexcrichton
cd3f21b 
Bump hashbrown to 0.4.0

Fixes #61357

This also includes rust-lang/hashbrown#80.
@Aaron1011
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I think it would be a good idea to add a run-pass to check that these auto-trait impls don't change again.

@gnzlbg
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gnzlbg commented Jun 2, 2019 •
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@Aaron1011 might make sense to add them as tests to most collections. Vec, VecDeque, etc. don't have tests for these either. I've made this error in some of my collections (changing some internal implementation detail and breaking users that rely on auto traits working "like before").

pietroalbini pushed a commit to pietroalbini/rust that referenced this issue Jun 6, 2019
@Amanieu @pietroalbini
Bump hashbrown to 0.4.0
b87df1c 
Fixes rust-lang#61357
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Bump hashbrown to 0.4.0 Amanieu/rust
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@cuviper @Amanieu @gnzlbg @Aaron1011 @aclonegeek