fixes #3338

tests/metatype/ttypeor.nim

@@ -0,0 +1,35 @@
+discard """
+  output: '''Foo
+Bar'''
+"""
+
+# bug #3338
+
+type
+  Base[T] = Foo[T] | Bar[T]
+
+  Foo[T] = ref object
+    x: T
+
+  Bar[T] = ref object
+    x: T
+
+proc test[T](ks: Foo[T], x, y: T): T =
+  echo("Foo")
+  return x + y + ks.x
+
+proc test[T](ks: Bar[T], x, y: T): T =
+  echo("Bar")
+  return x
+
+proc add[T](ksa: Base[T]) =
+  var test = ksa.test(5, 10)
+  ksa.x = test
+
+var t1 = Foo[int32]()
+t1.add()
+doAssert t1.x == 15
+
+var t2 = Bar[int32]()
+t2.add()
+doAssert t2.x == 5