1 files changed, 96 insertions, 0 deletions
diff --git a/tests/generics/trecursivegenerics.nim b/tests/generics/trecursivegenerics.nim
new file mode 100644
index 000000000..1b152b063
--- /dev/null
+++ b/tests/generics/trecursivegenerics.nim
@@ -0,0 +1,96 @@
+block: # Replicates #18728
+  type
+    FlipFlop[A, B] = ref object
+      val: A
+      next: FlipFlop[B, A]
+  
+    Trinary[A, B, C] = ref object
+      next: Trinary[B, C, A]
+  
+  assert typeof(FlipFlop[int, string]().next) is FlipFlop[string, int]
+  assert typeof(FlipFlop[string, int]().next) is FlipFlop[int, string]
+  assert typeof(Trinary[int, float, string]().next) is Trinary[float, string, int]
+  assert typeof(Trinary[int, float, string]().next.next) is Trinary[string, int, float]
+  var a = FlipFlop[int, string](val: 100, next: FlipFlop[string, int](val: "Hello"))
+  assert a.val == 100
+  assert a.next.val == "Hello"
+
+block: # 18838
+  type
+    DoublyLinkedNodeObj[T] = object
+      value: T
+
+    DoublyLinkedNode[T] = ref DoublyLinkedNodeObj[T]
+
+    Item[T] = ref object
+      link: DoublyLinkedNode[Item[T]]
+
+    Box = object
+
+  proc newDoublyLinkedNode[T](value: T): DoublyLinkedNode[T] =
+    new(result)
+    result.value = value 
+
+  let link = newDoublyLinkedNode(Item[Box]())
+
+import lists
+block:
+  type
+    Box = object
+    Item[T] = ref object
+      link:DoublyLinkedNode[ Item[T] ]
+
+    ItemSimple = ref object
+      link:DoublyLinkedNode[ ItemSimple ]
+
+  let link = newDoublyLinkedNode( Item[Box]() )
+
+block: #18897
+  type
+    SkipListObj[T] = object
+      over: SkipList[T]
+      down: SkipList[T]
+      value: T
+
+    SkipList[T] = ref SkipListObj[T]
+
+    GraphObj[N, E; F: static[int]] = object
+      nodes: SkipList[Node[N, E]]
+
+    Graph[N, E; F: static[int]] = ref GraphObj[N, E, F]
+
+    Node[N, E] = ref NodeObj[N, E]
+
+    NodeObj[N, E] = object
+      value: N
+      incoming: SkipList[Edge[N, E]]
+      outgoing: SkipList[Edge[N, E]]
+
+    Edge[N, E] = ref EdgeObj[N, E]
+
+    EdgeObj[N, E] = object
+      value: E
+      id: int
+      source: Node[N, E]
+      target: Node[N, E]
+
+    EdgeResult[N, E] = tuple
+      source: Node[N, E]
+      edge: Edge[N, E]
+      target: Node[N, E]
+
+  proc newSkipList[T](value: T): SkipList[T] =
+    static: echo T, " ", typeof(result.value)
+    result = SkipList[T](value: value)
+
+  proc toSkipList[T](values: openArray[T] = @[]): SkipList[T] =
+    for item in items(values):
+      if result.isNil:
+        result = newSkipList(item)
+
+  proc newContainer[N, E, F](graph: Graph[N, E, F]; form: typedesc): auto =
+    result = toSkipList[form]([])
+
+  var
+    result = Graph[int, string, 0]()
+  result.nodes = result.newContainer(Node[int, string])
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