Style/RedundantRegexpArgument auto-correct to wrong unterminated string from a single-quote regexp /\'/ #14543
Description
After auto-correct the following script, syntax error occurred.
source code:
require 'strscan'
module AAA
def check_single_quote(str)
ss = StringScanner.new(str)
ss.scan(/\'/)
end
end.rubocop.yml:
AllCops:
NewCops: enable
Expected behavior
Auto-corrected script runs without error.
Actual behavior
The above script is auto-corrected to the following script:
require 'strscan'
module AAA
def check_single_quote(str)
ss = StringScanner.new(str)
ss.scan('\\'')
end
endRunning the auto-corrected script, the following error occurred.
$ ruby tmp09.rb
tmp09.rb: --> tmp09.rb
Unmatched `(', missing `)' ?
2 module AAA
3 def check_single_quote(str)
> 4 ss = StringScanner.new(str)
> 5 ss.scan('\\'')
6 end
7 end
tmp09.rb:5: syntax errors found (SyntaxError)
3 | def check_single_quote(str)
4 | ss = StringScanner.new(str)
> 5 | ss.scan('\\'')
| ^ unterminated string meets end of file
6 | end
7 | end
> 8 |
| ^ expected an `end` to close the `module` statement
| ^ expected an `end` to close the `def` statement
| ^ unexpected end-of-input, assuming it is closing the parent top level context
| ^ unexpected end-of-input; expected a `)` to close the arguments
$
Steps to reproduce the problem
RuboCop log:
$ rubocop -d -a tmp09.rb
For /XXXX/202509/.rubocop.yml
Default configuration from /YYYY/amd64/3.4.6/lib/ruby/gems/3.4.0/gems/rubocop-1.80.2/config/default.yml
Use parallel by default.
Skipping parallel inspection: only a single file needs inspection
Inspecting 1 file
Scanning /XXXX/202509/tmp09.rb
Loading cache from /XXXX/.cache/rubocop_cache/178c5ca2f83a8cb4cb3064ce06de0eff8fa19ca9/6d7a3b621ca1730e04accd938619e4bdab66cfb1/fe41aad91eefe86e96fb2109a56bdc0594a75e65
F
Offenses:
tmp09.rb:5:13: C: [Corrected] Style/RedundantRegexpArgument: Use string '\\'' as argument instead of regexp /\'/.
ss.scan(/\'/)
^^^^
tmp09.rb:5:14: C: [Corrected] Style/RedundantRegexpEscape: Redundant escape inside regexp literal
ss.scan(/\'/)
^^
tmp09.rb:5:17: F: Lint/Syntax: unterminated string meets end of file
(Using Ruby 2.7 parser; configure using TargetRubyVersion parameter, under AllCops)
ss.scan('\\'')
^
1 file inspected, 3 offenses detected, 2 offenses corrected
Finished in 0.32895121996989474 seconds
$
RuboCop version
$ rubocop -V
1.80.2 (using Parser 3.3.9.0, rubocop-ast 1.46.0, analyzing as Ruby 2.7, running on ruby 3.4.6) [x86_64-linux]
$ ruby -v
ruby 3.4.6 (2025-09-16 revision dbd83256b1) +PRISM [x86_64-linux]
$ cat .rubocop.yml
AllCops:
NewCops: enable
$