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Add HashTable::iter_hash, HashTable::iter_hash_mut#549

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bors merged 3 commits into
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Sep 2, 2024
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Add HashTable::iter_hash, HashTable::iter_hash_mut#549
bors merged 3 commits into
rust-lang:masterfrom
the-mikedavis:md/hash-table-iter-hash

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@the-mikedavis

@the-mikedavis the-mikedavis commented Aug 28, 2024

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This is a follow-up to #546 (comment). iter_hash from the old raw API can be useful for reading from a "bag" / "multi map" type which allows duplicate key-value pairs. Exposing it safely in HashTable takes a fairly small wrapper around RawIterHash. This PR partially reverts #546 to restore RawTable::iter_hash and its associated types.
@the-mikedavis
Restore RawTable::iter_hash
e39e46e 
This partially reverts 26ef4a1 so that
the child commit can expose a safe `iter_hash` in
`HashTable::iter_hash`.
@the-mikedavis
Add HashTable::iter_hash
f40a539 
This is a safe wrapper around `RawTable::iter_hash`. `iter_hash` can be
useful for looking up duplicate values in the table. For example you
might use it to build a "bag" / "multi map" type which blindly inserts
with `HashTable::insert_unique` and allows lookup of multiple values for
the same key.
@Amanieu

Amanieu commented Aug 28, 2024

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Should there be a mut version of this iterator? What about removing one item out of multiple with the same key? Do we also need to add APIs for those use cases?
@the-mikedavis

the-mikedavis commented Aug 28, 2024

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For my use-case I will only need to read entries as-is after insertion. I could see mutation being useful hypothetically though. Maybe that could benefit from some kind of iterator that returns Entry-like items?
@Amanieu

Amanieu commented Aug 28, 2024

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Returning Entry doesn't work because you then end up with multiples Entrys each of which has a mutable reference to the table, which violates aliasing rules. I think just adding iter_hash_mut for now would be enough.
@the-mikedavis the-mikedavis force-pushed the md/hash-table-iter-hash branch from ab005f6 to 8b60594 Compare August 28, 2024 23:19
@the-mikedavis the-mikedavis changed the title Add HashTable::iter_hash Aug 28, 2024
@Amanieu

Amanieu commented Sep 2, 2024

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@bors r+
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bors commented Sep 2, 2024

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📌 Commit 8b60594 has been approved by Amanieu

It is now in the queue for this repository.
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bors commented Sep 2, 2024

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⌛ Testing commit 8b60594 with merge a69af93...
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bors commented Sep 2, 2024

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☀️ Test successful - checks-actions
Approved by: Amanieu
Pushing a69af93 to master...
@bors bors merged commit a69af93 into rust-lang:master Sep 2, 2024
@bors bors mentioned this pull request Sep 2, 2024
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@the-mikedavis the-mikedavis deleted the md/hash-table-iter-hash branch September 2, 2024 12:46
@the-mikedavis

the-mikedavis commented Sep 2, 2024

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Thanks @Amanieu! My multi map type is much cleaner as a HashTable now :)
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