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regex-syntax: fix nest limit checker
This commit fixes an embarrassing bug where the depth in the nest limit checker was never decremented during postorder traversal, which means long but shallow regexes would incorrectly trip the nest limit. We fix that in this commit and add two regression tests. Fixes #454
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lines changed

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‎CHANGELOG.md

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Original file line numberDiff line numberDiff line change
@@ -1,3 +1,11 @@
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TBD
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===
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Bug gixes:
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* [BUG #454](https://github.com/rust-lang/regex/pull/454):
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Fix a bug in the nest limit checker being too aggressive.
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19
0.2.7 (2018-03-07)
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==================
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This release includes a ground-up rewrite of the regex-syntax crate, which has

‎regex-syntax/src/ast/parse.rs

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Original file line numberDiff line numberDiff line change
@@ -2106,7 +2106,7 @@ impl<'p, 's, P: Borrow<Parser>> NestLimiter<'p, 's, P> {
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fn decrement_depth(&mut self) {
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// Assuming the correctness of the visitor, this should never drop
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// below 0.
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self.depth.checked_sub(1).unwrap();
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self.depth = self.depth.checked_sub(1).unwrap();
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}
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}
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@@ -5254,4 +5254,47 @@ bar
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],
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})));
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}
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// This tests a bug fix where the nest limit checker wasn't decrementing
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// its depth during post-traversal, which causes long regexes to trip
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// the default limit too aggressively.
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#[test]
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fn regression_454_nest_too_big() {
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let pattern = r#"
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2(?:
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[45]\d{3}|
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7(?:
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1[0-267]|
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2[0-289]|
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3[0-29]|
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4[01]|
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5[1-3]|
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6[013]|
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7[0178]|
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91
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)|
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8(?:
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0[125]|
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[139][1-6]|
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2[0157-9]|
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41|
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6[1-35]|
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7[1-5]|
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8[1-8]|
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90
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)|
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9(?:
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0[0-2]|
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1[0-4]|
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2[568]|
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3[3-6]|
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5[5-7]|
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6[0167]|
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7[15]|
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8[0146-9]
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)
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)\d{4}
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"#;
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assert!(parser_nest_limit(pattern, 50).parse().is_ok());
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}
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}

‎tests/crazy.rs

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Original file line numberDiff line numberDiff line change
@@ -103,3 +103,299 @@ fn dfa_handles_pathological_case() {
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};
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assert!(re.is_match(text!(&*text)));
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}
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#[test]
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fn nest_limit_makes_it_parse() {
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use regex::RegexBuilder;
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RegexBuilder::new(
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r#"
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2(?:
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[45]\d{3}|
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7(?:
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1[0-267]|
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2[0-289]|
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3[0-29]|
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4[01]|
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5[1-3]|
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6[013]|
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7[0178]|
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91
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)|
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8(?:
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0[125]|
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[139][1-6]|
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2[0157-9]|
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41|
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6[1-35]|
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7[1-5]|
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8[1-8]|
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90
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)|
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9(?:
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0[0-2]|
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1[0-4]|
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2[568]|
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3[3-6]|
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5[5-7]|
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6[0167]|
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7[15]|
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8[0146-9]
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)
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)\d{4}|
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3(?:
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12?[5-7]\d{2}|
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0(?:
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2(?:
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[025-79]\d|
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[348]\d{1,2}
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)|
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3(?:
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[2-4]\d|
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[56]\d?
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)
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)|
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2(?:
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1\d{2}|
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2(?:
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[12]\d|
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[35]\d{1,2}|
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4\d?
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)
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)|
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3(?:
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1\d{2}|
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2(?:
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[2356]\d|
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4\d{1,2}
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)
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)|
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4(?:
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1\d{2}|
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2(?:
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2\d{1,2}|
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[47]|
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5\d{2}
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)
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)|
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5(?:
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1\d{2}|
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29
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)|
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[67]1\d{2}|
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8(?:
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1\d{2}|
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2(?:
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2\d{2}|
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3|
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4\d
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)
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)
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)\d{3}|
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4(?:
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0(?:
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2(?:
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[09]\d|
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7
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)|
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33\d{2}
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)|
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1\d{3}|
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2(?:
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1\d{2}|
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2(?:
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[25]\d?|
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[348]\d|
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[67]\d{1,2}
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)
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)|
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3(?:
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1\d{2}(?:
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\d{2}
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)?|
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2(?:
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[045]\d|
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[236-9]\d{1,2}
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)|
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32\d{2}
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)|
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4(?:
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[18]\d{2}|
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2(?:
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[2-46]\d{2}|
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3
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)|
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5[25]\d{2}
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)|
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5(?:
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1\d{2}|
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2(?:
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3\d|
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5
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)
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)|
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6(?:
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[18]\d{2}|
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2(?:
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3(?:
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\d{2}
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)?|
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[46]\d{1,2}|
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5\d{2}|
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7\d
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)|
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5(?:
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3\d?|
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4\d|
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[57]\d{1,2}|
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6\d{2}|
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8
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)
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)|
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71\d{2}|
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8(?:
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[18]\d{2}|
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23\d{2}|
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54\d{2}
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)|
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9(?:
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[18]\d{2}|
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2[2-5]\d{2}|
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53\d{1,2}
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)
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)\d{3}|
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5(?:
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02[03489]\d{2}|
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1\d{2}|
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2(?:
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1\d{2}|
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2(?:
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2(?:
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\d{2}
275+
)?|
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[457]\d{2}
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)
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)|
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3(?:
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1\d{2}|
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2(?:
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[37](?:
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\d{2}
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)?|
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[569]\d{2}
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)
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)|
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4(?:
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1\d{2}|
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2[46]\d{2}
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)|
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5(?:
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1\d{2}|
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26\d{1,2}
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)|
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6(?:
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[18]\d{2}|
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2|
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53\d{2}
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)|
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7(?:
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1|
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24
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)\d{2}|
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8(?:
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1|
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26
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)\d{2}|
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91\d{2}
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)\d{3}|
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6(?:
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0(?:
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1\d{2}|
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2(?:
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3\d{2}|
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4\d{1,2}
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)
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)|
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2(?:
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2[2-5]\d{2}|
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5(?:
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[3-5]\d{2}|
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7
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)|
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8\d{2}
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)|
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3(?:
328+
1|
329+
2[3478]
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)\d{2}|
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4(?:
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1|
333+
2[34]
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)\d{2}|
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5(?:
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1|
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2[47]
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)\d{2}|
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6(?:
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[18]\d{2}|
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6(?:
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2(?:
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2\d|
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[34]\d{2}
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)|
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5(?:
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[24]\d{2}|
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3\d|
349+
5\d{1,2}
350+
)
351+
)
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)|
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72[2-5]\d{2}|
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8(?:
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1\d{2}|
356+
2[2-5]\d{2}
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)|
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9(?:
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1\d{2}|
360+
2[2-6]\d{2}
361+
)
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)\d{3}|
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7(?:
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(?:
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02|
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[3-589]1|
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6[12]|
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72[24]
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)\d{2}|
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21\d{3}|
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32
372+
)\d{3}|
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8(?:
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(?:
375+
4[12]|
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[5-7]2|
377+
1\d?
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)|
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(?:
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0|
381+
3[12]|
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[5-7]1|
383+
217
384+
)\d
385+
)\d{4}|
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9(?:
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[35]1|
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(?:
389+
[024]2|
390+
81
391+
)\d|
392+
(?:
393+
1|
394+
[24]1
395+
)\d{2}
396+
)\d{3}
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"#
398+
)
399+
.build()
400+
.unwrap();
401+
}

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