Array#rassoc should try to convert to array implicitly. Fixes #20003

[bolshakov]

Fixes https://bugs.ruby-lang.org/issues/20003

There is a difference between behaviour of Array#assoc and Array#rassoc. The first one performs implicit conversion (calls #to_ary) while the former does not.

class ArrayConvertible
  def initialize(*values)
    @values = values;
  end

  def to_ary
    @values
  end
end

s1 = [1, 2]
s2 = ArrayConvertible.new(2, 3)
a = [s1, s2]

The a.assoc(2) call returns [2, 3] as expected. However, a.rassoc(3) returns nil

Expected behaviour: a.rassoc(3) returns [2, 3] in such cases.

[bolshakov]

@mame now everything passed, except the spec I introduced here ruby/spec#1110 I will update it after the merge

[mame]

@bolshakov Could you update the mirrored spec file in this ruby/ruby repo directly? Changing ruby/spec is not reflected in real time. I want to keep the CI green.

[bolshakov]

@mame I updated the specs, and all checks are green now.