Bug #14048: Enumerable#sum sometimes assumes objects are `Range`s when they're not

• Status: Closed
• Assignee: mrkn (Kenta Murata)
• Target version: -
• ruby -v: ruby 2.4.2p198 (2017-09-14 revision 59899) [x86_64-darwin16]
• Backport: 2.3: UNKNOWN, 2.4: UNKNOWN

[rohitpaulk (Paul Kuruvilla)]

If a class defines the methods begin and end, Enumerable assumes that it is a Range object and tries to access the exclude_end? method.

class NotARange
  include Enumerable # Defines the `#sum` method

  def each
    yield 2
    yield 4
    yield 6
  end

  def begin; end
  def end; end
end

not_a_range = NotARange.new
puts not_a_range.sum

The above program throws an error:

main.rb:20:in `sum': undefined method `exclude_end?' for #<NotARange:0x00007f8750950c70> (NoMethodError)

If either begin or end are not defined though, it works fine and returns 12.

It looks like the commit that introduced this was: https://github.com/ruby/ruby/commit/53b4c2b87a9c6832e663cf5773a8aca9a1cf3341

I think that Enumerable should only attempt to perform the optimization on objects that are indeed Range or subclasses of Range.

[mrkn (Kenta Murata)]

• Assignee set to mrkn (Kenta Murata)

[nobu (Nobuyoshi Nakada)]

• Status changed from Open to Closed

Applied in changeset trunk|r60411.

---

range.c: check if exclude_end? is defined

• range.c (rb_range_values): should raise TypeError if necessary
  method is not defined, not NoMethodError, when trying to tell if
  the object is a Range and extract info.
  [ruby-core:83541] [Bug #14048]