Make Performance/Caller aware of caller_locations

[pocke]

caller and caller_locations are almost the same. They have difference in a type of return value. caller returns an Array<String>, but caller_locations returns an Array<Thread::Backtrace::Location>.
The difference is not problematic for this cop. So, I'll make this cop aware of caller_locations by this change.

Benchmark

require 'benchmark'

def method_for_backtrace
  tap do
    tap do
      yield
    end
  end
end

def assert(a, b)
  raise "#{a} != #{b}" if a != b
end

method_for_backtrace do
  assert(caller, caller_locations.map(&:to_s))
  assert(caller_locations.first.to_s, caller_locations(1..1).first.to_s)
  assert(caller_locations[1].to_s, caller_locations(2..2).first.to_s)

  Benchmark.bm(30) do |x|
    x.report('caller_locations.first')      {1000000.times{caller_locations.first}}
    x.report('caller_locations(1..1).first'){1000000.times{caller_locations(1..1).first}}

    x.report('caller_locations[1]')         {1000000.times{caller_locations[1]}}
    x.report('caller_locations(2..2).first'){1000000.times{caller_locations(2..2).first}}
  end
end

                                     user     system      total        real
caller_locations.first           1.660000   0.000000   1.660000 (  1.656021)
caller_locations(1..1).first     0.390000   0.000000   0.390000 (  0.392523)
caller_locations[1]              1.660000   0.000000   1.660000 (  1.661755)
caller_locations(2..2).first     0.460000   0.000000   0.460000 (  0.462888)

---

Before submitting the PR make sure the following are checked:

• Wrote good commit messages.
• Commit message starts with [Fix #issue-number] (if the related issue exists).
• Used the same coding conventions as the rest of the project.
• Feature branch is up-to-date with master (if not - rebase it).
• Squashed related commits together.
• Added tests.
• Added an entry to the Changelog if the new code introduces user-observable changes. See changelog entry format.
• All tests(rake spec) are passing.
• The new code doesn't generate RuboCop offenses that are checked by rake internal_investigation.
• The PR relates to only one subject with a clear title
  and description in grammatically correct, complete sentences.
• Updated cop documentation with rake generate_cops_documentation (required only when you've added a new cop or changed the configuration/documentation of an existing cop).

[Drenmi]

Would it work with:

(send nil {:caller :caller_locations} {int nil})

? 🤔

[pocke]

Hmm, it does not work. Because the matcher checks children size. https://github.com/bbatsov/rubocop/blob/master/lib/rubocop/node_pattern.rb#L201

I think if ? operator like regular expression is added to the matcher, it is handy.
For example:

# int is optional.
(send nil {:caller :caller_locations} int?)

However, this syntax is conflict with existing one 😢

[Drenmi]

Yeah. We'd need to come up with something that is available. Will look into this later. 🙂

[Drenmi]

There's a #first_argument method on parameterized nodes, that could be used here, and on L:51. 😊

[Drenmi]

Great change! It looks like the two node matchers can be combined? Because the result of #caller_with_scope_method? is just passed on to #slow_caller?. WDYT? 🙂

[pocke]

@Drenmi I updated. Thanks!