class Sass::Tree::Visitors::Cssize

def visit_mixin(node)
  # Don't use #visit_children to avoid adding the mixin node to the list of parents.
  node.children.map {|c| visit(c)}.flatten
rescue Sass::SyntaxError => e
  e.modify_backtrace(:mixin => node.name, :filename => node.filename, :line => node.line)
  e.add_backtrace(:filename => node.filename, :line => node.line)
  raise e
end