Reference Parent Schema in Child Schema

interface ParentChildEncoded { data: string, child?: ParentChild | undefined }
interface ParentChildType extends ParentChildEncoded { parent?: ParentChild }
type ParentChild$ = S.Schema<ParentChildType, ParentChildEncoded>
const fields = {
  data: S.String,
  child: S.optional(S.suspend((): ParentChild$ => ParentChild))
}
class ParentChild extends S.Class<ParentChild>('ParentChild')(fields) {
  readonly parent?: ParentChild
}

const parent = new ParentChild({
  data: 'The parent',
  child: {
    data: 'The Child',
    parent: () => parent // <-- Need a thunk here?
  }
})