sinatra: `caller_locations': wrong number of arguments (given 2, expected 0) (ArgumentError)

[deepj]

truffleruby 20.1.0-dev-d6e1b291, like ruby 2.6.5, GraalVM CE Native [x86_64-darwin]

This is minimal reproducible code extracted from ruby_event_store-browser. The problem lies in https://github.com/sinatra/sinatra/blob/master/lib/sinatra/base.rb#L1514 It's in conflict with Kernel.caller_locations. No issue under MRI though.

To reproduce:

gem install sinatra
rackup

config.ru

require 'sinatra/base'

class MyApp < Sinatra::Base
  def self.for(host: nil, path: nil, environment: :production)
    self.tap do |app|
      app.settings.instance_exec do
        set :public_folder, "#{__dir__}/../../../public"
      end
    end
  end
end

run MyApp.for

Error:

~/.gem/truffleruby/2.6.5/gems/sinatra-2.0.8.1/lib/sinatra/base.rb:1514:in `caller_locations': wrong number of arguments (given 2, expected 0) (ArgumentError)
	from ~/dev/truffleruby/bugs/sinatra/config.ru:8:in `__dir__'
	from ~/dev/truffleruby/bugs/sinatra/config.ru:8:in `block (2 levels) in for'
	from ~/dev/truffleruby/bugs/sinatra/config.ru:7:in `instance_exec'
	from ~/dev/truffleruby/bugs/sinatra/config.ru:7:in `block in for'
	from ~/dev/truffleruby/bugs/sinatra/config.ru:6:in `tap'
	from ~/dev/truffleruby/bugs/sinatra/config.ru:6:in `for'

[norswap]

Minimal reprod:

p __dir__ # ok
def caller_locations
  'override'
end
p __dir__ # nope

[norswap]

Fixed in 1de99bf