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do not suggest capturing '_ twice in use<...> for E0700 - #163471
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the test records what the compiler prints today: for an opaque that already has use<'_> and a second anonymous lifetime to capture, it suggested use<'_, '_>, which doesnt compile
suggest_precise_capturing was appending '_ to a use<..> list that already had it, suggesting use<'_, '_>, which rustc rejects with cannot capture parameter '_ twice the branch for an opaque with an existing use<..> now bails out the same way the branch for an opaque without one does: both check if the lifetime is already captured
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'_ twice in use<...> for E0700
oli-obk
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Sep 29, 2026
| @@ -1 +1 @@ | |||
| error[E0700]: hidden type for `impl Sized` captures lifetime that does not appear in bounds | |||
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would this test pass if rustfix were run on it? if so, you can make it a rustfix test to ensure this doesn't regress
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just checked, it cant be a rustfix test. after the fix dup gets no suggestion, so the .fixed file still fails E0700 and compiletest requires it to compile.
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Reminder, once the PR becomes ready for a review, use |
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@rustbot ready |
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Thanks for checking @bors r+ rollup |
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thanks for the review! |
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…uwer Rollup of 4 pull requests Successful merges: - #163024 (Add `Dir` equivalents of `fs::metadata` & `fs::symlink_metadata`) - #162839 (Bump min Emscripten version to 4.0, drop deprecated -sWASM_BIGINT for wasm32-unknown-emscripten) - #163370 (Fix incorrect typo suggestion for `struct field` shorthands) - #163471 (do not suggest capturing `'_` twice in `use<...>` for E0700)
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Rollup merge of #163471 - Albab-Hasan:no-duplicate-anon-lifetime-capture-suggestion, r=oli-obk do not suggest capturing `'_` twice in `use<...>` for E0700 starting from `use<'_>` with a second anonymous lifetime to capture, E0700 suggests `use<'_, '_>`. that fails with: ``` error: cannot capture parameter `'_` twice ``` then the compiler suggests `use<'_, '_, '_>`. both `AddPreciseCapturing::New` and `AddPreciseCapturing::Existing` are `machine-applicable` (rustc_trait_selection/src/diagnostics.rs:1876 and :1888) so rustfix applies the broken edit. the branch for an opaque without `use<..>` already skips lifetimes that are captured. this adds the same check to the branch for an existing `use<..>`. the issue repro compiles clean on edition 2024 and needs 2021 so the test starts one step in with `use<'_>` already written. two extra cases check the guard stays narrow: `use<>` with one anonymous lifetime still gets `use<'_>` and a named lifetime still gets suggested by name. one note. the guard removes the suggestion without replacing it so someone who already wrote `use<'_>` gets no path forward. a correct suggestion needs to name the elided lifetimes and suggest_precise_capturing cannot do that today. that the multipart suggestion this issue asks for will be the follow up. #132199 r? @oli-obk
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…uwer Rollup of 4 pull requests Successful merges: - rust-lang/rust#163024 (Add `Dir` equivalents of `fs::metadata` & `fs::symlink_metadata`) - rust-lang/rust#162839 (Bump min Emscripten version to 4.0, drop deprecated -sWASM_BIGINT for wasm32-unknown-emscripten) - rust-lang/rust#163370 (Fix incorrect typo suggestion for `struct field` shorthands) - rust-lang/rust#163471 (do not suggest capturing `'_` twice in `use<...>` for E0700)
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starting from
use<'_>with a second anonymous lifetime to capture, E0700 suggestsuse<'_, '_>. that fails with:then the compiler suggests
use<'_, '_, '_>. bothAddPreciseCapturing::NewandAddPreciseCapturing::Existingaremachine-applicable(rustc_trait_selection/src/diagnostics.rs:1876 and :1888) so rustfix applies the broken edit.the branch for an opaque without
use<..>already skips lifetimes that are captured. this adds the same check to the branch for an existinguse<..>.the issue repro compiles clean on edition 2024 and needs 2021 so the test starts one step in with
use<'_>already written. two extra cases check the guard stays narrow:use<>with one anonymous lifetime still getsuse<'_>and a named lifetime still gets suggested by name.one note. the guard removes the suggestion without replacing it so someone who already wrote
use<'_>gets no path forward. a correct suggestion needs to name the elided lifetimes and suggest_precise_capturing cannot do that today. that the multipart suggestion this issue asks for will be the follow up.#132199
r? @oli-obk