class Sass::Script::Tree::Interpolation

def to_string_interpolation(node_or_interp)
  unless node_or_interp.is_a?(Interpolation)
    node = node_or_interp
    return string_literal(node.value.to_s) if node.is_a?(Literal)
    if node.is_a?(StringInterpolation)
      return concat(string_literal(node.quote), concat(node, string_literal(node.quote)))
    end
    return StringInterpolation.new(string_literal(""), node, string_literal(""))
  end
  interp = node_or_interp
  after_string_or_interp =
    if interp.after
      to_string_interpolation(interp.after)
    else
      string_literal("")
    end
  if interp.after && interp.whitespace_after
    after_string_or_interp = concat(string_literal(' '), after_string_or_interp)
  end
  mid_string_or_interp = to_string_interpolation(interp.mid)
  before_string_or_interp =
    if interp.before
      to_string_interpolation(interp.before)
    else
      string_literal("")
    end
  if interp.before && interp.whitespace_before
    before_string_or_interp = concat(before_string_or_interp, string_literal(' '))
  end
  concat(before_string_or_interp, concat(mid_string_or_interp, after_string_or_interp))
end