Improve diagnostics for buffer reuse with borrowed references#147974

JohnTitor · 2025-10-22T12:13:27Z

I'm not sure the current note wording is the best so I appreciate any feedback.

rustbot · 2025-10-22T12:13:30Z

This PR modifies tests/ui/issues/. If this PR is adding new tests to tests/ui/issues/,
please refrain from doing so, and instead add it to more descriptive subdirectories.

rustbot · 2025-10-22T12:13:33Z

r? @jackh726

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JohnTitor · 2025-10-22T12:13:43Z

r? @estebank

JohnTitor · 2025-10-22T12:16:54Z

compiler/rustc_borrowck/src/diagnostics/conflict_errors.rs

+                                    )
+                                );
+                                err.help(
+                                    "buffer reuse with borrowed references requires unsafe code or restructuring"


Didn't mention recycle_vec as I'm not sure if using that crate is the most common solution here.

There's an RFC to bring that into std, so we can change this once we have that.

estebank · 2025-11-11T21:55:05Z

tests/ui/borrowck/buffer-reuse-pattern-issue-147694.stderr

+LL |         buffer.clear();
+   |         ------ borrow later used here


This is specifically (one of) the pattern(s) that we should detect in order to suggest recycling in the future.

estebank · 2025-11-11T21:56:26Z

@bors r+

Leaving the ticket open to not forget to come back to this and provide structured suggestions when possible.

Thank you for taking a look at this!

bors · 2025-11-11T21:56:29Z

📌 Commit 61b26f9 has been approved by estebank

It is now in the queue for this repository.

…ttern, r=estebank Improve diagnostics for buffer reuse with borrowed references Addresses rust-lang#147694 I'm not sure the current note wording is the best so I appreciate any feedback.

Rollup of 12 pull requests Successful merges: - #146627 (Simplify `jemalloc` setup) - #147753 (Suggest add bounding value for RangeTo) - #147974 (Improve diagnostics for buffer reuse with borrowed references) - #148080 ([rustdoc] Fix invalid jump to def macro link generation) - #148424 (bootstrap: Add snapshot tests for path-to-step handling) - #148500 (Update git index before running diff-index) - #148536 (cmse: add test for `async` and `const` functions) - #148770 (implement `feature(c_variadic_naked_functions)`) - #148819 (Remove specialized warning for removed target) - #148830 (miri subtree update) - #148833 (Update rustbook dependencies) - #148841 (Remove more `#[must_use]` from portable-simd) r? `@ghost` `@rustbot` modify labels: rollup

bors · 2025-11-12T01:25:04Z

⌛ Testing commit 61b26f9 with merge ad650e3...

…tebank Improve diagnostics for buffer reuse with borrowed references Addresses #147694 I'm not sure the current note wording is the best so I appreciate any feedback.

Zalathar · 2025-11-12T01:27:20Z

Yielding to enclosing rollup.

@bors retry

Rollup of 16 pull requests Successful merges: - #146627 (Simplify `jemalloc` setup) - #147753 (Suggest add bounding value for RangeTo) - #147832 (rustdoc: Don't pass `RenderOptions` to `DocContext`) - #147974 (Improve diagnostics for buffer reuse with borrowed references) - #148080 ([rustdoc] Fix invalid jump to def macro link generation) - #148465 (Adjust spans into the `for` loops context before creating the new desugaring spans.) - #148500 (Update git index before running diff-index) - #148531 (rustc_target: introduce Abi, Env, Os) - #148536 (cmse: add test for `async` and `const` functions) - #148770 (implement `feature(c_variadic_naked_functions)`) - #148780 (fix filecheck typos in tests) - #148819 (Remove specialized warning for removed target) - #148830 (miri subtree update) - #148833 (Update rustbook dependencies) - #148834 (fix(rustdoc): Color doctest errors) - #148841 (Remove more `#[must_use]` from portable-simd) r? `@ghost` `@rustbot` modify labels: rollup

bors · 2025-11-12T04:42:51Z

⌛ Testing commit 61b26f9 with merge 0b329f8...

Rollup merge of #147974 - JohnTitor:diag-detect-buf-reuse-pattern, r=estebank Improve diagnostics for buffer reuse with borrowed references Addresses #147694 I'm not sure the current note wording is the best so I appreciate any feedback.

Rollup of 16 pull requests Successful merges: - rust-lang/rust#146627 (Simplify `jemalloc` setup) - rust-lang/rust#147753 (Suggest add bounding value for RangeTo) - rust-lang/rust#147832 (rustdoc: Don't pass `RenderOptions` to `DocContext`) - rust-lang/rust#147974 (Improve diagnostics for buffer reuse with borrowed references) - rust-lang/rust#148080 ([rustdoc] Fix invalid jump to def macro link generation) - rust-lang/rust#148465 (Adjust spans into the `for` loops context before creating the new desugaring spans.) - rust-lang/rust#148500 (Update git index before running diff-index) - rust-lang/rust#148531 (rustc_target: introduce Abi, Env, Os) - rust-lang/rust#148536 (cmse: add test for `async` and `const` functions) - rust-lang/rust#148770 (implement `feature(c_variadic_naked_functions)`) - rust-lang/rust#148780 (fix filecheck typos in tests) - rust-lang/rust#148819 (Remove specialized warning for removed target) - rust-lang/rust#148830 (miri subtree update) - rust-lang/rust#148833 (Update rustbook dependencies) - rust-lang/rust#148834 (fix(rustdoc): Color doctest errors) - rust-lang/rust#148841 (Remove more `#[must_use]` from portable-simd) r? `@ghost` `@rustbot` modify labels: rollup

Improve diagnostics for buffer reuse with borrowed references

61b26f9

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 Oct 22, 2025

rustbot assigned jackh726 Oct 22, 2025

rustbot assigned estebank and unassigned jackh726 Oct 22, 2025

JohnTitor commented Oct 22, 2025

View reviewed changes

estebank reviewed Nov 11, 2025

View reviewed changes

bors 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 Nov 11, 2025

Zalathar mentioned this pull request Nov 11, 2025

Rollup of 13 pull requests #148844

Closed

Zalathar mentioned this pull request Nov 11, 2025

Rollup of 12 pull requests #148845

Closed

Zalathar mentioned this pull request Nov 12, 2025

Rollup of 16 pull requests #148851

Merged

bors merged commit b98d127 into rust-lang:main Nov 12, 2025
11 of 12 checks passed

rustbot added this to the 1.93.0 milestone Nov 12, 2025

JohnTitor deleted the diag-detect-buf-reuse-pattern branch November 12, 2025 09:16

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Improve diagnostics for buffer reuse with borrowed references#147974