Generalize std::str::Pattern to be generic over the haystack and rehome it - #161606
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Generalize std::str::Pattern to be generic over the haystack and rehome it#161606pacak wants to merge 3 commits into
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cc @Amanieu, @folkertdev, @sayantn |
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r? @JohnTitor rustbot has assigned @JohnTitor. Use Why was this reviewer chosen?The reviewer was selected based on:
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I'm not sure what's the right approach here. Sync it after this lands? A separate pull request? |
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This is fine, it's a tiny change, we'll handle the sync after it merges. |
This was referenced Aug 23, 2026
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r? @nia-e |
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#161608 (review) - I'm going to try this |
Right now things are undertested and underspecified. Some of the library code would get in a loop if searcher starts returning empty rejects. And there's no tests for backwards multi byte char matchers. Pull request I'm reviving had a problem implementing that, so making sure it's tested before the actual code lands. Right now it is possible to break both tests (and user code) without breaking anything else in the test suite I think.
Add a Haystack trait describing something that can be searched in and make core::str::Pattern (and related types) generic on that trait. This will allow Pattern to be used for types other than str (most notably OsStr). This somewhat follows the Pattern API 2.0 design. While that design is apparently abandoned (?), it is somewhat helpful when going for patterns on OsStr, so I’m going with it unless someone tells me otherwise. ;) For now leave Pattern, Haystack et al in core::str::pattern. Since they are no longer str-specific, I’ll move them to core::pattern in future commit. This one leaves them in place to make the diff smaller. @pacak: I moved some (or all new) of the `P: Pattern<&'a str> constraints into where clause to keep things narrower: ``` pub fn foo<'a, P: Pattern<&'a str>>(&'a self, pat: P, ...) ... ``` to ``` pub fn replacen<'a, P>(&'a self, pat: P, ...) ... where P: Pattern<&'a str>, ``` Original code had indices in Haystack abstracted as an associated type Cursor. Replaced with usize - Cursor adds noise with not much value. Changed wording in 2-3 places - for example Searcher is generic over a few types so it makes more sense to talk about split points in general with utf8 split points as an example for `&str`.
Pattern is no longer str-specific, so move it from core::str::pattern module to a new core::pattern module. This introduces no changes in behaviour or implementation. Just moves stuff around and adjusts documentation.
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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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OsStrspecifically)core::str::Patterntocore::pattern::Patternto reflect thatNot very useful on its own, but required to extend pattern splitting API to
OsStr.Contains changes from #161604, I'll rebase one that test lands.
Part of the #160971 cinematic universe.