get rid of dependency on list

Author: bobzhang

immut/priority_queue/moon.pkg.json

@@ -2,7 +2,6 @@
   "import": [
     "moonbitlang/core/builtin",
     "moonbitlang/core/iter",
-    "moonbitlang/core/list",
     "moonbitlang/core/array",
     "moonbitlang/core/assertion",
     "moonbitlang/core/coverage"

immut/priority_queue/priority_queue.mbt

@@ -52,7 +52,13 @@ pub fn to_array[T : Compare](self : ImmutablePriorityQueue[T]) -> Array[T] {
     match x {
       Node(v, child) => {
         arr.push(v)
-        child.iter(fn(v) { go(v) }) |> ignore
+        loop child {
+          Nil => ()
+          Cons(x, xs) => {
+            go(x)
+            continue xs
+          }
+        }
       }
       Empty => ()
     }