Nulls

Because we don't have null, we need null.

 type Null union <
   Elem interface{}
 > [
   Null struct{}
   Value Elem
 ]
 
 var foo Null<int> = Foo()
 if foo.Null? {
   return foo
 }
 // at this point, the compiler knows that foo must be case Value
 // so in this instance, i now has a type of int
 return i*20