Add test

Author: liufengyun

tests/neg-custom-args/isInstanceOf/i17435.scala

@@ -0,0 +1,23 @@
+import scala.collection.mutable
+
+object Test:
+  type JsonPrimitive = String | Int | Double | Boolean | None.type
+
+  type Rec[JA[_], JO[_], A] = A match
+    case JsonPrimitive => JsonPrimitive | JA[Rec[JA, JO, JsonPrimitive]] | JO[Rec[JA, JO, JsonPrimitive]]
+    case _ => A | JA[Rec[JA, JO, A]] | JO[Rec[JA, JO, A]]
+
+  type Json = Rec[[A] =>> mutable.Buffer[A], [A] =>> mutable.Map[String, A], JsonPrimitive]
+
+  type JsonObject = mutable.Map[String, Json]
+
+  type JsonArray = mutable.Buffer[Json]
+
+  def encode(x: Json): Int = x match
+    case str: String => 1
+    case b: Boolean => 2
+    case i: Int => 3
+    case d: Double => 4
+    case arr: JsonArray => 5    // error
+    case obj: JsonObject => 6   // error
+    case _ => 7