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Remove Clone impl for StableHashingContext.#154744

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rust-bors[bot] merged 1 commit intorust-lang:mainfrom
nnethercote:rm-Clone-for-StableHashingContext
Apr 6, 2026
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Remove Clone impl for StableHashingContext.#154744
rust-bors[bot] merged 1 commit intorust-lang:mainfrom
nnethercote:rm-Clone-for-StableHashingContext

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@nnethercote nnethercote commented Apr 3, 2026 •
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HashStable::hash_stable takes a &mut Hcx. In contrast, ToStableHashKey::to_stable_hash_key takes a &Hcx. But there are some places where the latter calls the former, and due to the mismatch a clone call is required to get a mutable StableHashingContext.

This commit changes to_stable_hash_key to instead take a &mut Hcx. This eliminates the mismatch, the need for the clones, and the need for the Clone impls.

r? @fee1-dead

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Remove Clone impl for StableHashingContext.
ff1795f 
`HashStable::hash_stable` takes a `&mut Hcx`. In contrast,
`ToStableHashKey::to_stable_hash_key` takes a `&Hcx`. But there are
some places where the latter calls the former, and due to the mismatch a
`clone` call is required to get a mutable `StableHashingContext`.

This commit changes `to_stable_hash_key` to instead take a `&mut Hcx`.
This eliminates the mismatch, the need for the clones, and the need for
the `Clone` impls.
@rustbot rustbot added S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. T-compiler Relevant to the compiler team, which will review and decide on the PR/issue. labels Apr 3, 2026
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nnethercote commented Apr 3, 2026

@bors try @rust-timer queue

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rust-bors bot pushed a commit that referenced this pull request Apr 3, 2026
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Auto merge of #154744 - nnethercote:rm-Clone-for-StableHashingContext…
b67d172 
…, r=<try>

Remove `Clone` impl for `StableHashingContext`.
@rustbot rustbot added the S-waiting-on-perf Status: Waiting on a perf run to be completed. label Apr 3, 2026
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rust-bors bot commented Apr 3, 2026

☀️ Try build successful (CI)
Build commit: b67d172 (b67d172374c3229c5c67970f61c951ccc3d2641b, parent: 55e86c996809902e8bbad512cfb4d2c18be446d9)

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rust-timer commented Apr 3, 2026

Finished benchmarking commit (b67d172): comparison URL.

Overall result: no relevant changes - no action needed

Benchmarking this pull request means it may be perf-sensitive – we'll automatically label it not fit for rolling up. You can override this, but we strongly advise not to, due to possible changes in compiler perf.

@bors rollup=never
@rustbot label: -S-waiting-on-perf -perf-regression

Instruction count

This benchmark run did not return any relevant results for this metric.

Max RSS (memory usage)

Results (primary -1.0%)

A less reliable metric. May be of interest, but not used to determine the overall result above.

mean range count
Regressions ❌
(primary)		 - - 0
Regressions ❌
(secondary)		 - - 0
Improvements ✅
(primary)		 -1.0% [-1.0%, -1.0%] 1
Improvements ✅
(secondary)		 - - 0
All ❌✅ (primary) -1.0% [-1.0%, -1.0%] 1

Cycles

This benchmark run did not return any relevant results for this metric.

Binary size

This benchmark run did not return any relevant results for this metric.

Bootstrap: 486.952s -> 486.532s (-0.09%)
Artifact size: 395.04 MiB -> 395.07 MiB (0.01%)

@rustbot rustbot removed the S-waiting-on-perf Status: Waiting on a perf run to be completed. label Apr 3, 2026
@nnethercote nnethercote marked this pull request as ready for review April 3, 2026 08:47
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rustbot commented Apr 3, 2026

fee1-dead is not on the review rotation at the moment.
They may take a while to respond.

@rustbot rustbot added the S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. label Apr 3, 2026
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rustbot commented Apr 3, 2026

The Miri subtree was changed

cc @rust-lang/miri

@rustbot rustbot removed the S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. label Apr 3, 2026
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nnethercote commented Apr 3, 2026

This PR makes hash_stable and to_stable_hash_key match by making them both use &mut Hcx. I also tried making them both use &Hcx (by using interior mutability) in #154735 but it was a slight performance regression.

@nnethercote nnethercote mentioned this pull request Apr 3, 2026
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fee1-dead commented Apr 6, 2026

@bors r+ rollup

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rust-bors bot commented Apr 6, 2026

📌 Commit ff1795f has been approved by fee1-dead

It is now in the queue for this repository.

@rust-bors rust-bors bot added S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. and removed S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels Apr 6, 2026
@jhpratt jhpratt mentioned this pull request Apr 6, 2026
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rust-bors bot pushed a commit that referenced this pull request Apr 6, 2026
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Auto merge of #154862 - jhpratt:rollup-mjtl7mx, r=jhpratt
c2efcc4 
Rollup of 4 pull requests

Successful merges:

 - #152853 (deny-by-default & report in deps `uninhabited_static`)
 - #153615 (fixed generics of crate node ICE)
 - #154744 (Remove `Clone` impl for `StableHashingContext`.)
 - #154841 (add regression test for Redundant memory strores with mut parameters …)
@rust-bors rust-bors bot merged commit 24223a6 into rust-lang:main Apr 6, 2026
12 checks passed
@rustbot rustbot added this to the 1.96.0 milestone Apr 6, 2026
rust-timer added a commit that referenced this pull request Apr 6, 2026
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Unrolled build for #154744
b6aefac 
Rollup merge of #154744 - nnethercote:rm-Clone-for-StableHashingContext, r=fee1-dead

Remove `Clone` impl for `StableHashingContext`.

`HashStable::hash_stable` takes a `&mut Hcx`. In contrast, `ToStableHashKey::to_stable_hash_key` takes a `&Hcx`. But there are some places where the latter calls the former, and due to the mismatch a `clone` call is required to get a mutable `StableHashingContext`.

This commit changes `to_stable_hash_key` to instead take a `&mut Hcx`. This eliminates the mismatch, the need for the clones, and the need for the `Clone` impls.

r? @fee1-dead
@nnethercote nnethercote deleted the rm-Clone-for-StableHashingContext branch April 6, 2026 22:53
github-actions bot pushed a commit to rust-lang/miri that referenced this pull request Apr 7, 2026
@bors
Auto merge of #154862 - jhpratt:rollup-mjtl7mx, r=jhpratt
9940865 
Rollup of 4 pull requests

Successful merges:

 - rust-lang/rust#152853 (deny-by-default & report in deps `uninhabited_static`)
 - rust-lang/rust#153615 (fixed generics of crate node ICE)
 - rust-lang/rust#154744 (Remove `Clone` impl for `StableHashingContext`.)
 - rust-lang/rust#154841 (add regression test for Redundant memory strores with mut parameters …)
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