Phantom Type Parameters with Branded Types for Compile-Time State Verification

declare const StateBrand: unique symbol;
 
type State<S extends string> = { readonly [StateBrand]: S };
 
type Draft = State<"DRAFT">;
type Published = State<"PUBLISHED">;
 
type Document<S extends State<string>> = {
  id: string;
  content: string;
  _state: S;
};
 
function createDocument(content: string): Document<Draft> {
  return { id: "doc-1", content, _state: null as any };
}
 
function publishDocument(doc: Document<Draft>): Document<Published> {
  return { ...doc, _state: null as any };
}