Issue #15938 has been updated by nobu (Nobuyoshi Nakada).

Status changed from Closed to Rejected

`\w` cannot be an edge of range in char-class, as it is not a single char.

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Bug #15938: Error thrown undeterministically: `RegexpError: empty range in char class`
https://bugs.ruby-lang.org/issues/15938#change-78696

* Author: dlee (David Lee)
* Status: Rejected
* Priority: Normal
* Assignee: 
* Target version: 
* ruby -v: 2.4.6
* Backport: 2.4: UNKNOWN, 2.5: UNKNOWN, 2.6: UNKNOWN
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When instantiating a Regexp, we only sometimes see `RegexpError: empty range in char class`.

To reproduce:
`100.times { Regexp.new("^([\\w'+-.%]+@[\\w-.]+\\.[A-Za-z]{2,25})(,[\\w+-.%]+@[\\w-.]+\\.[A-Za-z]{2,4}){0,4}$") }`
usually does not throw the error, but
`100000.times { Regexp.new("^([\\w'+-.%]+@[\\w-.]+\\.[A-Za-z]{2,25})(,[\\w+-.%]+@[\\w-.]+\\.[A-Za-z]{2,4}){0,4}$") }`
usually throws the error.

Furthermore, sometimes accompanying calls matter:
`10.times { Regexp.new("[\\w-.]"); Regexp.new("[\\w-]") }`
usually does not throw the error, but
`10.times { Regexp.new("[\\w-.]") }`
usually throws the error.



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