borrowck diagnostics: make add_move_error_suggestions use the HIR rather than SourceMap
#133486
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dianne
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Nov 26, 2024
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To be honest, I'm not sure why the "consider borrowing the pattern bindings" lines weren't in this test's output before; they appeared when I tested it on the playground. Either way, the suggestions look okay1 to me, though I'm not a deref-patterns expert.
Footnotes
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Apart from being non-
run-rustfix-able, due to the type errors resulting from binding by-reference. ↩
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…r=estebank borrowck diagnostics: make `add_move_error_suggestions` use the HIR rather than `SourceMap` This PR aims to fix rust-lang#132806 by rewriting `add_move_error_suggestions`[^1]. Previously, it manually scanned the source text to find a leading `&`, which isn't always going to produce a correct result (see: that issue). Admittedly, the HIR visitor in this PR introduces a lot of boilerplate, but hopefully the logic at its core isn't too complicated (I go over it in the comments). I also tried a simpler version that didn't use a HIR visitor and suggested adding `ref` always, but the `&ref x` suggestions really didn't look good. As a bonus for the added complexity though, it's now able to produce nice `&`-removing suggestions in more cases. I tried to do this such that it avoids edition-dependent checks and its suggestions can be applied together with those from the match ergonomics 2024 migration lint. I haven't added tests for that since the details of match ergonomics 2024 are still being sorted out, but I can try if desired once that's finalized. [^1]: In brief, it fires on patterns where users try to bind by-value in such a way that moves out of a reference to a non-Copy type (including slice references with non-copy elements). The suggestions are to change the binding's mode to be by-reference, either by removing[^2] an enclosing `&`/`&mut` or adding `ref` to the binding. [^2]: Incidentally, I find the terminology of "consider removing the borrow" a bit confusing for a suggestion to remove a `&` pattern in order to make bindings borrow rather than move. I'm not sure what a good, concise way to explain that would be though, and that should go in a separate PR anyway.
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Rollup of 9 pull requests Successful merges: - rust-lang#132474 (Add more mailmap entries) - rust-lang#133486 (borrowck diagnostics: make `add_move_error_suggestions` use the HIR rather than `SourceMap`) - rust-lang#134063 (dec2flt: Clean up float parsing modules) - rust-lang#134861 (Add GUI test for item info elements color) - rust-lang#134968 (Print how to rebless Python formatting in tidy) - rust-lang#134971 (chore: fix typos) - rust-lang#134972 (add .mailmap entry for myself) - rust-lang#134974 (Revert rust-lang#119515 single line where clause style guide) - rust-lang#134975 (Revert style guide rhs break) r? `@ghost` `@rustbot` modify labels: rollup
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Rollup of 8 pull requests Successful merges: - rust-lang#132474 (Add more mailmap entries) - rust-lang#133486 (borrowck diagnostics: make `add_move_error_suggestions` use the HIR rather than `SourceMap`) - rust-lang#134861 (Add GUI test for item info elements color) - rust-lang#134968 (Print how to rebless Python formatting in tidy) - rust-lang#134971 (chore: fix typos) - rust-lang#134972 (add .mailmap entry for myself) - rust-lang#134974 (Revert rust-lang#119515 single line where clause style guide) - rust-lang#134975 (Revert style guide rhs break) r? `@ghost` `@rustbot` modify labels: rollup
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Rollup merge of rust-lang#133486 - dianne:fix-move-error-suggestion, r=estebank borrowck diagnostics: make `add_move_error_suggestions` use the HIR rather than `SourceMap` This PR aims to fix rust-lang#132806 by rewriting `add_move_error_suggestions`[^1]. Previously, it manually scanned the source text to find a leading `&`, which isn't always going to produce a correct result (see: that issue). Admittedly, the HIR visitor in this PR introduces a lot of boilerplate, but hopefully the logic at its core isn't too complicated (I go over it in the comments). I also tried a simpler version that didn't use a HIR visitor and suggested adding `ref` always, but the `&ref x` suggestions really didn't look good. As a bonus for the added complexity though, it's now able to produce nice `&`-removing suggestions in more cases. I tried to do this such that it avoids edition-dependent checks and its suggestions can be applied together with those from the match ergonomics 2024 migration lint. I haven't added tests for that since the details of match ergonomics 2024 are still being sorted out, but I can try if desired once that's finalized. [^1]: In brief, it fires on patterns where users try to bind by-value in such a way that moves out of a reference to a non-Copy type (including slice references with non-copy elements). The suggestions are to change the binding's mode to be by-reference, either by removing[^2] an enclosing `&`/`&mut` or adding `ref` to the binding. [^2]: Incidentally, I find the terminology of "consider removing the borrow" a bit confusing for a suggestion to remove a `&` pattern in order to make bindings borrow rather than move. I'm not sure what a good, concise way to explain that would be though, and that should go in a separate PR anyway.
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This PR aims to fix #132806 by rewriting
add_move_error_suggestions1. Previously, it manually scanned the source text to find a leading&, which isn't always going to produce a correct result (see: that issue). Admittedly, the HIR visitor in this PR introduces a lot of boilerplate, but hopefully the logic at its core isn't too complicated (I go over it in the comments). I also tried a simpler version that didn't use a HIR visitor and suggested addingrefalways, but the&ref xsuggestions really didn't look good. As a bonus for the added complexity though, it's now able to produce nice&-removing suggestions in more cases.I tried to do this such that it avoids edition-dependent checks and its suggestions can be applied together with those from the match ergonomics 2024 migration lint. I haven't added tests for that since the details of match ergonomics 2024 are still being sorted out, but I can try if desired once that's finalized.
Footnotes
In brief, it fires on patterns where users try to bind by-value in such a way that moves out of a reference to a non-Copy type (including slice references with non-copy elements). The suggestions are to change the binding's mode to be by-reference, either by removing2 an enclosing
&/&mutor addingrefto the binding. ↩Incidentally, I find the terminology of "consider removing the borrow" a bit confusing for a suggestion to remove a
&pattern in order to make bindings borrow rather than move. I'm not sure what a good, concise way to explain that would be though, and that should go in a separate PR anyway. ↩