如何在Dhall中编码多个深度的规则树？

let RuleTree =
  < Leaf : Text
  | Node : List RuleTree
  >

let ruleTree =
  [ Node [ Node [ Leaf "Rule 1" ]
         , Node [ Leaf "Rule 2" ]
         ]
  , Node [ Leaf "Rule 3" ]
  ]

let printRules : List RuleTree -> Text
    = \(trees : List RuleTree) ->
      let printTree : RuleTree -> Text
          = \(tree : RuleTree) ->
            merge
              { Leaf = \(text : Text) -> text
              , Node = \(nodes : List RuleTree) -> printRules nodes
              }
              tree
      in  Text.concat (List.map printTree trees)

in  printRules ruleTree