LiteralInInterpolation false positive when interpolating "#{__LINE__}"

[rrosenblum]

I just upgraded to RuboCop 0.30.0 and ran into a false positive when running LiteralInInterpolation.

Here is a test that exercises the bug.

it 'accepts strings like __LINE__' do
  inspect_source(cop, '"this is #{__LINE__} silly"')
  expect(cop.offenses).to be_empty
end


1) RuboCop::Cop::Lint::LiteralInInterpolation accepts strings like __LINE__
     Failure/Error: expect(cop.offenses).to be_empty
       expected `[W:  1: 12: Literal interpolation detected.].empty?` to return true, got false

I will try to find a fix for the issue, but in the mean time, I wanted to bring exposure to the bug.

[rrosenblum]

I am not sure of the proper way to fix this. After looking into the code, the error is caused by "#{__LINE__}" having the type :int and "#{__FILE__}" having the type :str. When I update the method special_string? to account for :int, the tests for "#{1}" begin to fail. I cannot figure out a way to distinguish between "#{__LINE__}" and "#{1}" without looking at the actual source.

[jonas054]

I think you must look at the actual source to sort out this special case.

node.loc.expression.is?('__LINE__')

[bbatsov]

Yeah, that should solve it. Unfortunately its a somewhat expensive check, but I can think of no other alternatives.