Fix transmutability type mismatch bug by lsunsi · Pull Request #163946 · rust-lang/rust

lsunsi · 2026-10-07T14:46:53Z

The change was done as instructed by @ShoyuVanilla and @lcnr on Zulip.
There are some leftover questions I'll add as comments (self review).
But the original examples are both fixed.

rustbot · 2026-10-07T14:46:59Z

Some changes occurred to the core trait solver

cc @rust-lang/initiative-trait-system-refactor

These commits modify the Cargo.lock file. Unintentional changes to Cargo.lock can be introduced when switching branches and rebasing PRs.

If this was unintentional then you should revert the changes before this PR is merged.
Otherwise, you can ignore this comment.

rustbot · 2026-10-07T14:47:02Z

ShoyuVanilla is currently at their maximum review capacity.
They may take a while to respond.

lcnr · 2026-10-12T12:07:26Z

@bors delegate+

rust-bors · 2026-10-12T12:07:29Z

✌️ @lsunsi, you can now approve this pull request!

If @lcnr told you to "r=me" after making some further change, then please make that change and post @bors r=lcnr.

View changes since this delegation.

ShoyuVanilla · 2026-10-12T13:52:23Z

@bors r=lcnr,ShoyuVanilla rollup

rust-bors · 2026-10-12T13:52:27Z

📌 Commit 13694b6 has been approved by lcnr,ShoyuVanilla

It is now in the queue for this repository.

@ShoyuVanilla

…uVanilla Fix transmutability type mismatch bug Fixes rust-lang#161251 r? @ShoyuVanilla The change was done as instructed by @ShoyuVanilla and @lcnr on Zulip. There are some leftover questions I'll add as comments (self review). But the original examples are both fixed.

@ShoyuVanilla

…uVanilla Fix transmutability type mismatch bug Fixes rust-lang#161251 r? @ShoyuVanilla The change was done as instructed by @ShoyuVanilla and @lcnr on Zulip. There are some leftover questions I'll add as comments (self review). But the original examples are both fixed.

…uwer Rollup of 8 pull requests Successful merges: - #164196 (`rust-analyzer` subtree update) - #164037 (Restrict application of optimization attributes from instance) - #164201 (Improve `--bless` output for `tests/debuginfo`) - #164202 ([rustdoc] Move the creation of `IndividualTestOptions` into the test runner closure to ensure the temporary folder is removed right after the test is done running) - #162140 (fn_addr_eq: we actually can guarantee basically nothing) - #163946 (Fix transmutability type mismatch bug) - #163978 (Copy over some methods from At to InferCtxt) - #164045 (-Zassumptions-on-binders: replace region vars with bound vars when handling alias outlives')

@ShoyuVanilla

Rollup merge of #163946 - lsunsi:next-transmute, r=lcnr,ShoyuVanilla Fix transmutability type mismatch bug Fixes #161251 r? @ShoyuVanilla The change was done as instructed by @ShoyuVanilla and @lcnr on Zulip. There are some leftover questions I'll add as comments (self review). But the original examples are both fixed.

lcnr · 2026-10-12T21:49:07Z

@lsunsi does this fix the issues added in #163946?

lsunsi · 2026-10-12T21:55:38Z

@lcnr do you mean #161251? If so, yes, it fixes it.

lcnr · 2026-10-13T07:40:43Z

yikes xd, I meant #149228 😅

lsunsi · 2026-10-13T10:12:19Z

@lcnr ./x test tests/ui/transmutability/transmutability-coherence.rs --compare-mode next-solver

The test added in #149228 passes cleanly on compare mode.
I'm not sure why the current PR is equivalent to the referred change, but it seems to be.

Do you want me to open a PR with just the new test? Or maybe just close the PR directly?

lcnr · 2026-10-13T10:27:15Z

please add these tests in a separate PR, yeah 😊

lsunsi · 2026-10-13T10:54:33Z

@lcnr here we go #164257 (:

EDIT: forgot to assign you as reviewer. should be a trivial approve, should I re-assign you?

Add transmutability test to cover for superseded PR Adds a test present in rust-lang#149228 that was fixed by rust-lang#163946.

Rollup merge of #164257 - lsunsi:pull149228, r=ShoyuVanilla Add transmutability test to cover for superseded PR Adds a test present in #149228 that was fixed by #163946.

…uwer Rollup of 8 pull requests Successful merges: - rust-lang/rust#164196 (`rust-analyzer` subtree update) - rust-lang/rust#164037 (Restrict application of optimization attributes from instance) - rust-lang/rust#164201 (Improve `--bless` output for `tests/debuginfo`) - rust-lang/rust#164202 ([rustdoc] Move the creation of `IndividualTestOptions` into the test runner closure to ensure the temporary folder is removed right after the test is done running) - rust-lang/rust#162140 (fn_addr_eq: we actually can guarantee basically nothing) - rust-lang/rust#163946 (Fix transmutability type mismatch bug) - rust-lang/rust#163978 (Copy over some methods from At to InferCtxt) - rust-lang/rust#164045 (-Zassumptions-on-binders: replace region vars with bound vars when handling alias outlives')

rustbot added S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. T-compiler Relevant to the compiler team, which will review and decide on the PR/issue. WG-trait-system-refactor The Rustc Trait System Refactor Initiative (-Znext-solver) labels Oct 7, 2026

rustbot assigned ShoyuVanilla Oct 7, 2026

lsunsi commented Oct 7, 2026

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Comment thread compiler/rustc_next_trait_solver/src/solve/trait_goals.rs Resolved

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Comment thread compiler/rustc_next_trait_solver/Cargo.toml Resolved

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Comment thread compiler/rustc_next_trait_solver/src/solve/mod.rs Resolved

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Comment thread compiler/rustc_next_trait_solver/src/solve/trait_goals.rs Resolved

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lcnr reviewed Oct 7, 2026

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Comment thread compiler/rustc_next_trait_solver/src/solve/trait_goals.rs Resolved

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Comment thread compiler/rustc_next_trait_solver/src/solve/mod.rs Resolved

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Comment thread tests/ui/transmutability/vec-recycle-next-solver.rs Resolved

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lsunsi force-pushed the next-transmute branch from 07cad77 to 3148361 Compare October 9, 2026 20:25

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lsunsi force-pushed the next-transmute branch from 2efe77b to 73189a9 Compare October 10, 2026 13:32

lsunsi added 4 commits October 10, 2026 10:37

Uplift flatten_answer_tree to next-solver

c1c3daa

Add test for transmute recycle on next solver

61d4201

Update is_transmutable on next solver to consider nested goals

01d70ab

Update test to reflect previous fix

247b4de

Drop two repeated tests and an unecessary directive

13694b6

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 Oct 12, 2026

JonathanBrouwer mentioned this pull request Oct 12, 2026

Rollup of 9 pull requests #164211

Closed

This was referenced Oct 12, 2026

Rollup of 9 pull requests #164212

Closed

Rollup of 8 pull requests #164216

Merged

rust-bors Bot merged commit cee2a0d into rust-lang:main Oct 12, 2026
14 checks passed

rustbot added this to the 1.101.0 milestone Oct 12, 2026

lsunsi deleted the next-transmute branch October 12, 2026 20:07

funsafemath mentioned this pull request Oct 13, 2026

Assume::NOTHING doesn't check lifetimes #164246

Closed

lcnr mentioned this pull request Oct 13, 2026

transmutability: Stall new solver when inference variables remain #149228

Closed

lsunsi mentioned this pull request Oct 13, 2026

Add transmutability test to cover for superseded PR #164257

Merged

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