class Bundler::PubGrub::VersionRange

def span(other)

(if they aren't you are probably calling the wrong method)
If self and other are contiguous, this builds a union of the two ranges.

The span covered by two ranges 
def span(other)
  return self if other.empty?
  min_range =
    if !min
      self
    elsif !other.min
      other
    else
      case min <=> other.min
      when 0
        include_min ? self : other
      when -1
        self
      when 1
        other
      end
    end
  max_range =
    if !max
      self
    elsif !other.max
      other
    else
      case max <=> other.max
      when 0
        include_max ? self : other
      when -1
        other
      when 1
        self
      end
    end
  VersionRange.new(
    min: min_range.min,
    include_min: min_range.include_min,
    max: max_range.max,
    include_max: max_range.include_max
  )
end