Add test

Author: liufengyun

tests/pos/i9782.scala

@@ -0,0 +1,19 @@
+trait Txn[T <: Txn[T]]
+
+trait Elem[T <: Txn[T]]
+
+trait Obj[T <: Txn[T]] extends Elem[T]
+
+trait Copy[In <: Txn[In], Out <: Txn[Out]] {
+  def copyImpl[Repr[~ <: Txn[~]] <: Elem[~]](in: Repr[In]): Repr[Out]
+  
+  def apply[Repr[~ <: Txn[~]] <: Elem[~]](in: Repr[In]): Repr[Out] = {
+    val out = copyImpl[Repr](in)
+    (in, out) match {
+      case (inObj: Obj[In], outObj: Obj[Out]) =>     // problem here
+        println("copy the attributes")
+      case _ =>
+    }
+    out
+  }
+}