Lint/OutOfRangeRegexpRef picks wrong regex

[ysbaddaden]

Actual behavior

Lint/OutOfRangeRegexpRef seems confused when multiple regular expressions are present on a single line, and picks the wrong Regex, leading to false positives and true negatives.

Steps to reproduce the problem

In the following example Lint/OutOfRangeRegexpRef seems to pick the first Regex, in the gsub call (/\s+/), instead of the final Regex that is populating $1 (/foo(bar)/):

if "foo bar".gsub(/\s+/, "") =~ /foo(bar)/
  p $1
end

x.rb:2:5: W: Lint/OutOfRangeRegexpRef: Do not use out of range reference for the Regexp.
  p $1
    ^^

Rubocop won't complain anymore when the Regex in the gsub call is modified to capture, but still won't complain when changing the second regex to not capture:

if "foo bar".gsub(/(\s+)/, "") =~ /foobar/
  p $1 # always nil
end

RuboCop version

0.90.0 (using Parser 2.7.1.4, rubocop-ast 0.4.0, running on ruby 2.6.6 x86_64-linux-musl)

[ysbaddaden]

Here is another weird example. This time Lint/OutOfRangeRegexpRef will pick the following /\s{2}/ Regex, despite being a match call on $1 itself:

if "some : line " =~ / : (.+)/
  $1.gsub(/\s{2}/, " ")
end

x.rb:2:3: W: Lint/OutOfRangeRegexpRef: Do not use out of range reference for the Regexp.
  $1.gsub(/\s{2}/, " ")
  ^^