fixes yet another option type

tests/objvariant/tyaoption.nim

@@ -0,0 +1,47 @@
+discard """
+  output: '''some(str), some(5), none
+some(5!)
+some(10)'''
+"""
+
+import strutils
+
+type Option[A] = object
+  case isDefined*: Bool
+    of true:
+      value*: A
+    of false:
+      nil
+
+proc some[A](value: A): Option[A] =
+  Option[A](isDefined: true, value: value)
+
+proc none[A](): Option[A] =
+  Option[A](isDefined: false)
+
+proc `$`[A](o: Option[A]): String =
+  if o.isDefined:
+    "some($1)" % [$o.value]
+  else:
+    "none"
+
+let x = some("str")
+let y = some(5)
+let z = none[Int]()
+
+echo x, ", ", y, ", ", z
+
+proc intOrString[A : Int | String](o: Option[A]): Option[A] =
+  when A is Int:
+    some(o.value + 5)
+  elif A is String:
+    some(o.value & "!")
+  else:
+    o
+
+#let a1 = intOrString(none[String]())
+let a2 = intOrString(some("5"))
+let a3 = intOrString(some(5))
+#echo a1
+echo a2
+echo a3