Bug #19564: Range.cover? fails for Range wrapped in SimpleDelegator

• Status: Rejected
• Assignee: -
• Target version: -
• ruby -v: ruby 3.2.0 (2022-12-25 revision a528908271) [x86_64-darwin22]
• Backport: 2.7: UNKNOWN, 3.0: UNKNOWN, 3.1: UNKNOWN, 3.2: UNKNOWN

[PeteMichaud (Pete Michaud)]

test 'built-in cover? method is broken for SimpleDelegator' do

  class TimeRangeDelegator < SimpleDelegator
  end

  t1 = Time.now
  t2 = t1+1.day
  t3 = t1+1.week

  r_long = t1..t3
  r_short = t1..t2

  assert r_long.cover?(r_short) #passes correctly, assert == true

  r_long_delegated = TimeRangeDelegator.new(r_long)
  r_short_delegated = TimeRangeDelegator.new(r_short)

  assert r_long_delegated.cover?(r_short_delegated) #fails incorrectly, assert == false
end

[jeremyevans0 (Jeremy Evans)]

I'm not sure if this is a bug. There are many other cases where wrapping an object in a delegate changes behavior (e.g. if false vs. if SimpleDelegator.new(false)).

If we want to allow this to work, the most likely approach would be adding something like Range#to_range, and having Range#cover? try to use to_range to convert arguments if the arguments respond to to_range. I'm not sure the benefits of that are worth the costs.

[matz (Yukihiro Matsumoto)]

I have a few ideas to address the issue, but all of them have significant side-effect. I don't think it's worth making cover? to support Delegators, despite those side effect.

Matz.

[jeremyevans0 (Jeremy Evans)]

• Status changed from Open to Rejected