Syntax error auto-correcting Performance/RegexpMatch

[dduugg]

I'm getting a syntax error auto-correcting a Performance/RegexpMatch violation in the following method definition:

def foo(id)
  if id.=~(/\./)
    'yes'
  else
    'no'
  end
end

Expected behavior

I expect this to autocorrect to:

def foo(id)
  if /\./.match?(id)
    'yes'
  else
    'no'
  end
end

Actual behavior

The autocorrection has an extra ), leading to a syntax error:

def foo(id)
  if /\./.match?(id))
    'yes'
  else
    'no'
  end
end

Steps to reproduce the problem

Put the above snippet into a foo.rb file, then:

$ bundle exec rubocop foo.rb -a
Inspecting 1 file
E

Offenses:
foo.rb:4:6: C: [Corrected] Performance/RegexpMatch: Use match? instead of =~ when MatchData is not used.
  if id.=~(/\./)
     ^^^^^^^^^^^
foo.rb:7:21: E: Lint/Syntax: unexpected token tRPAREN
(Using Ruby 2.4 parser; configure using TargetRubyVersion parameter, under AllCops)
  if /\./.match?(id))
                    ^
foo.rb:9:3: W: Lint/Syntax: else without rescue is useless
(Using Ruby 2.4 parser; configure using TargetRubyVersion parameter, under AllCops)
  else
  ^^^^
foo.rb:12:1: E: Lint/Syntax: unexpected token kEND
(Using Ruby 2.4 parser; configure using TargetRubyVersion parameter, under AllCops)
end
^^^

RuboCop version

Include the output of rubocop -V or bundle exec rubocop -V if using Bundler. Here's an example:

$ bundle exec rubocop -V
0.69.0 (using Parser 2.6.2.0, running on ruby 2.4.5 x86_64-darwin17)

(rubocop-performance version is 1.3.0)

[tejasbubane]

@koic I was trying to fix this error and have a doubt. Both FOO =~ re and FOO.=~(re) produce the exact same AST:

 s(:send,
  s(:const, nil, :FOO), :=~,
  s(:send, nil, :re))

How can we differentiate between the two? without falling back to source string that is.