class Sass::Tree::Visitors::CheckNesting

def visit_children(parent)
  old_parent = @parent
  # When checking a static tree, resolve at-roots to be sure they won't send
  # nodes where they don't belong.
  if parent.is_a?(Sass::Tree::AtRootNode) && parent.resolved_value
    old_parents = @parents
    @parents = @parents.reject {|p| parent.exclude_node?(p)}
    @parent = Sass::Util.enum_with_index(@parents.reverse).
      find {|p, i| !transparent_parent?(p, @parents[-i - 2])}.first
    begin
      return super
    ensure
      @parents = old_parents
      @parent = old_parent
    end
  end
  unless transparent_parent?(parent, old_parent)
    @parent = parent
  end
  @parents.push parent
  begin
    super
  ensure
    @parent = old_parent
    @parents.pop
  end
end