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