Miscellaneous cleanups to borrowck related code #150550

BoxyUwU · 2025-12-31T17:20:50Z

r? lcnr

rustbot · 2025-12-31T17:20:53Z

Some changes occurred to the CTFE machinery

cc @RalfJung, @oli-obk, @lcnr

Some changes occurred to the CTFE / Miri interpreter

cc @rust-lang/miri

compiler/rustc_borrowck/src/borrow_set.rs

BoxyUwU · 2025-12-31T17:25:08Z

compiler/rustc_middle/src/mir/statement.rs

    /// Returns whether borrows represented by this kind are allowed to be split into separate
    /// Reservation and Activation phases.
-    pub fn allows_two_phase_borrow(&self) -> bool {
+    pub fn is_two_phase_borrow(&self) -> bool {


in some sense its always a two phase borrow, just sometimes its activated at the same point its created I think?

The previous name confused me because it made it sound like a reference may or may not be a two phase borrow and then we went on to unconditionally treat it as two phase without ever checking if it "actually is".

compiler/rustc_borrowck/src/type_check/free_region_relations.rs

lcnr · 2026-01-06T10:22:13Z

compiler/rustc_trait_selection/src/traits/query/type_op/implied_outlives_bounds.rs

+    // and we know that `&'a T::Out` is WF, then we want to imply `U: 'a`.
+    let normalized_ty = ocx
+        .deeply_normalize(&ObligationCause::dummy_with_span(span), param_env, ty)
+        .map_err(|_| NoSolution)?;


did you test removing the normalized_ty here and does that break anything?

it didn't break anything but I also didn't feel confident enough in our test suite to just yeet it 🤔 I guess the failure mode here is "less implied bounds" which is not unsound so it's probably quite safe to do, and it should be easy enough to bisect this PR from a crater regression

ah there were some weird diagnostic changes that I didn't want to spend the time investigating

specifically, tests/ui/delegation/unsupported.rs has its cycles changed to "cycle detected when comparing an impl" and we lose the type annotations needed error. I have literally no idea how delegation works so don't intend to look into that xd

compiler/rustc_borrowck/src/borrow_set.rs

lcnr · 2026-01-06T10:25:13Z

nits, then r=me

rustbot · 2026-01-19T16:13:20Z

This PR was rebased onto a different main commit. Here's a range-diff highlighting what actually changed.

Rebasing is a normal part of keeping PRs up to date, so no action is needed—this note is just to help reviewers.

lcnr · 2026-01-19T18:03:06Z

@bors r+ rollup

rust-bors · 2026-01-19T18:03:09Z

📌 Commit 3705ebb has been approved by lcnr

It is now in the queue for this repository.

@ghost

…uwer Rollup of 15 pull requests Successful merges: - #148623 (Ignore `#[doc(hidden)]` items when computing trimmed paths for printing) - #150550 (Miscellaneous cleanups to borrowck related code) - #150879 (Remove the diagnostic lints) - #150895 (rustc_errors: Add (heuristic) Syntax Highlighting for `rustc --explain`) - #150987 (remote-test-server: Fix header in batch mode) - #151004 (std: implement `sleep_until` on Apple platforms) - #151045 (Simplify some literal-value negations with `u128::wrapping_neg`) - #151119 (Support pointers in type reflection) - #151171 (Do not recover from `Trait()` if generic list is unterminated) - #151231 (HIR typeck cleanup: clarify and re-style `check_expr_unop`) - #151249 (Parse ident with allowing recovery when trying to diagnose) - #151295 (THIR patterns: Use `ty::Value` in more places throughout `const_to_pat`) - #151326 (Remove `DiagMessage::Translated` in favour of `DiagMessage::Str`) - #151361 (add test for issue 61463) - #151371 (Add `S-blocked` to `labels_blocking_approval`) r? @ghost

Rollup merge of #150550 - borrowck_cleanup_2, r=lcnr Miscellaneous cleanups to borrowck related code r? lcnr

@ghost

…uwer Rollup of 15 pull requests Successful merges: - rust-lang/rust#148623 (Ignore `#[doc(hidden)]` items when computing trimmed paths for printing) - rust-lang/rust#150550 (Miscellaneous cleanups to borrowck related code) - rust-lang/rust#150879 (Remove the diagnostic lints) - rust-lang/rust#150895 (rustc_errors: Add (heuristic) Syntax Highlighting for `rustc --explain`) - rust-lang/rust#150987 (remote-test-server: Fix header in batch mode) - rust-lang/rust#151004 (std: implement `sleep_until` on Apple platforms) - rust-lang/rust#151045 (Simplify some literal-value negations with `u128::wrapping_neg`) - rust-lang/rust#151119 (Support pointers in type reflection) - rust-lang/rust#151171 (Do not recover from `Trait()` if generic list is unterminated) - rust-lang/rust#151231 (HIR typeck cleanup: clarify and re-style `check_expr_unop`) - rust-lang/rust#151249 (Parse ident with allowing recovery when trying to diagnose) - rust-lang/rust#151295 (THIR patterns: Use `ty::Value` in more places throughout `const_to_pat`) - rust-lang/rust#151326 (Remove `DiagMessage::Translated` in favour of `DiagMessage::Str`) - rust-lang/rust#151361 (add test for issue 61463) - rust-lang/rust#151371 (Add `S-blocked` to `labels_blocking_approval`) r? @ghost

JonathanBrouwer · 2026-01-20T07:29:29Z

@rust-timer build f6790fd
Trying to find the perf regression in #151381

rust-timer · 2026-01-20T08:10:57Z

Finished benchmarking commit (f6790fd): 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 (secondary 5.2%)

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)	5.2%	[3.8%, 6.5%]	2
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-	-	0

Cycles

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

Binary size

Results (primary -0.0%, secondary -0.1%)

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)	-0.0%	[-0.1%, -0.0%]	10
Improvements ✅ (secondary)	-0.1%	[-0.1%, -0.0%]	22
All ❌✅ (primary)	-0.0%	[-0.1%, -0.0%]	10

Bootstrap: 473.058s -> 475.899s (0.60%)
Artifact size: 383.29 MiB -> 383.23 MiB (-0.02%)

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. labels Dec 31, 2025

rustbot assigned lcnr Dec 31, 2025

BoxyUwU commented Dec 31, 2025

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BoxyUwU commented Dec 31, 2025

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compiler/rustc_borrowck/src/type_check/free_region_relations.rs Show resolved Hide resolved

lcnr reviewed Jan 6, 2026

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lcnr added S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. and removed S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels Jan 19, 2026

BoxyUwU added 2 commits January 19, 2026 16:08

two phase borrow handling cleanups

169dadc

implied bounds comments

3705ebb

BoxyUwU force-pushed the borrowck_cleanup_2 branch from f799e2f to 3705ebb Compare January 19, 2026 16:13

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-author Status: This is awaiting some action (such as code changes or more information) from the author. labels Jan 19, 2026

JonathanBrouwer mentioned this pull request Jan 19, 2026

Rollup of 15 pull requests #151381

Merged

rust-bors bot merged commit a66a2e3 into rust-lang:main Jan 20, 2026
11 checks passed

rustbot added this to the 1.95.0 milestone Jan 20, 2026

rust-timer added a commit that referenced this pull request Jan 20, 2026

Unrolled build for #150550

f6790fd

Rollup merge of #150550 - borrowck_cleanup_2, r=lcnr Miscellaneous cleanups to borrowck related code r? lcnr

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Overall result: no relevant changes - no action needed

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BoxyUwU Jan 19, 2026 •

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