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Rust nightly removed the lifetime from Pattern #1219

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Merged
merged 3 commits into from
Aug 2, 2024
Merged

Rust nightly removed the lifetime from Pattern #1219

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e79febe
Rust nightly removed the lifetime from Pattern
mischnic Aug 2, 2024
b587720
Don't elide lifetime
mischnic Aug 2, 2024
8d87475
Rename lifetime
mischnic Aug 2, 2024
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6 changes: 3 additions & 3 deletions src/pattern.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -10,10 +10,10 @@ pub struct RegexSearcher<'r, 't> {
next_match: Option<(usize, usize)>,
}

impl<'r, 't> Pattern<'t> for &'r Regex {
type Searcher = RegexSearcher<'r, 't>;
impl<'r> Pattern for &'r Regex {
type Searcher<'t> = RegexSearcher<'r, 't>;

fn into_searcher(self, haystack: &'t str) -> RegexSearcher<'r, 't> {
fn into_searcher(self, haystack: &str) -> RegexSearcher<'r, '_> {
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Should this be?

fn into_searcher(self, haystack: &'t str) -> RegexSearcher<'r, 't> {

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This lifetime setup is also used by the various Pattern impls in the standard library:
rust-lang/rust@772315d

Your version doesn't compile directly, the first suggestion below is exactly what I have implemented now (but with 't being elided) and the second suggestion is what was used before my PR and now fails to compile.

error[E0261]: use of undeclared lifetime name `'t`
  --> src/pattern.rs:16:68
   |
16 |     fn into_searcher(self, haystack: &'t str) -> RegexSearcher<'r, 't> {
   |                                                                    ^^ undeclared lifetime
   |
help: consider introducing lifetime `'t` here
   |
16 |     fn into_searcher<'t>(self, haystack: &'t str) -> RegexSearcher<'r, 't> {
   |                     ++++
help: consider introducing lifetime `'t` here
   |
13 | impl<'t, 'r> Pattern for &'r Regex {
   |      +++

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I guess the problem I have here is how does the RegexSearcher connect its lifetime to the haystack? I must be missing something.

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@mischnic mischnic Aug 2, 2024 •
edited
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What I wrote here is equivalent to this, which is how the &str lifetime flows into the RegexSearcher lifetime (I can commit that instead if you want)

fn into_searcher<'h>(self, haystack: &'h str) -> RegexSearcher<'r, 'h>

Is that what you meant?

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Ooooo, yes, I get it now. Yes, please do write that. I'm usually fine with lifetime elision, but I think it actually helps a lot here.

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Right right. This all makes sense now. Got it. I was confused myself.

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Perfect 😄
I've added back that explicit lifetime

RegexSearcher {
haystack,
it: self.find_iter(haystack),
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