fixes #16754

[demotomohiro]

This PR allows passing the defining type to generic types in the right side in a type definition like this:

type
  Foo = object
    x: Option[Foo]

I think generic types should be instanciated after all given arguments are semchecked,
because generic types can access information about them.
(for example, Option[T] in std/option checks if T is a pointer like type)
But in this case, need to instanciate Option[Foo] before type of Foo.x is determined.