class Regexp::Parser

def decrease_nesting
  while nesting.last.is_a?(SequenceOperation)
    nesting.pop
    self.node = nesting.last
  end
  nesting.pop
  yield(node) if block_given?
  self.node = nesting.last
  self.node = node.last if node.last.is_a?(SequenceOperation)
end