Better error message when bare type in impl parameter list#157466
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The parser was modified, potentially altering the grammar of (stable) Rust cc @fmease |
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r? @adwinwhite rustbot has assigned @adwinwhite. Use Why was this reviewer chosen?The reviewer was selected based on:
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Sorry for being so slow. I should have rerolled earlier. Thought I would have time to look into the recovery mechanism. @rustbot reroll |
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Reminder, once the PR becomes ready for a review, use |
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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. |
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@bors r+ rollup |
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Better error message when bare type in impl parameter list Fixes rust-lang#147889 Marking this PR ready for feedback on this problem. The approach I'm trying is to create a snapshot parser and attempt to re-parse the input in another way. If it succeeds, we successfully predicted the user's intention and emit the related help message. If it fails, we cancel the errors produced during the attempt and report the original error. The problem is that parse functions may internally recover from parse failures and emit errors directly, which means we can't cancel them later. I saw that we have a `recovery` field to control the recovery mechanism, but it seems there are (maybe) a lot of places in the parser that don't check the recovery field before doing their recovery logic. Should we always use `look_ahead` instead of using a snapshot parser and calling another parse function?
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…uwer Rollup of 12 pull requests Successful merges: - #156976 (enable eager `param_env` norm in new solver) - #158537 (Add `std::io::cursor::WriteThroughCursor`) - #158540 (Move `std::io::Seek` to `core::io`) - #157820 (consider subtyping when checking if an infer var is sized) - #158505 (Update POSIX edition links) - #158853 (Fix typo for link on nto-qnx.md) - #157466 (Better error message when bare type in impl parameter list) - #157966 (Emit a suggestion to cast the never type into a concrete type when it fails to satisfy an `impl Trait` bound) - #158381 (Expose debug scope of statement and terminator in rustc_public) - #158405 (rustc_target: Add ARMv8-M related target features) - #158770 (Weaken guarantee for `From<legacy::RangeInclusive> for RangeInclusive`) - #158820 (Fix rustdoc ICE on deprecated note in inlined re-export chain)
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Rollup merge of #157466 - bb1yd:issue-147889, r=davidtwco Better error message when bare type in impl parameter list Fixes #147889 Marking this PR ready for feedback on this problem. The approach I'm trying is to create a snapshot parser and attempt to re-parse the input in another way. If it succeeds, we successfully predicted the user's intention and emit the related help message. If it fails, we cancel the errors produced during the attempt and report the original error. The problem is that parse functions may internally recover from parse failures and emit errors directly, which means we can't cancel them later. I saw that we have a `recovery` field to control the recovery mechanism, but it seems there are (maybe) a lot of places in the parser that don't check the recovery field before doing their recovery logic. Should we always use `look_ahead` instead of using a snapshot parser and calling another parse function?
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Fixes #147889
Marking this PR ready for feedback on this problem.
The approach I'm trying is to create a snapshot parser and attempt to re-parse the input in another way. If it succeeds, we successfully predicted the user's intention and emit the related help message. If it fails, we cancel the errors produced during the attempt and report the original error.
The problem is that parse functions may internally recover from parse failures and emit errors directly, which means we can't cancel them later. I saw that we have a
recoveryfield to control the recovery mechanism, but it seems there are (maybe) a lot of places in the parser that don't check the recovery field before doing their recovery logic.Should we always use
look_aheadinstead of using a snapshot parser and calling another parse function?