A solution to the problem where you want to distinguish identical data payload at both typechecking time and provide a way to inspect that type at runtime via values in TypeScript. Leverages branded parameter types with intersection types.

branded.ts

type Brand<Shared, EventType> = Shared & { readonly __eventType: EventType; };

type SharedCommentEventFields = {
  otherField: string;
};

type CommentFlagged = Brand<SharedCommentEventFields, 'CommentFlagged'>;
type CommentRec = Brand<SharedCommentEventFields, 'CommentRec'>;

const makeCommentFlagEvent = (eventFields: SharedCommentEventFields): CommentFlagged => (
  { __eventType: "CommentFlagged", ...eventFields }
);

const makeCommentRecEvent = (eventFields: SharedCommentEventFields): CommentRec => (
  { __eventType: "CommentRec", ...eventFields }
);

const flagEvent = makeCommentFlagEvent({ otherField: "foo" });
const recEvent = makeCommentRecEvent({ otherField: "foo" });

// uncomment to see that this fails to type check
// console.log(flagEvent === recEvent);

console.log(flagEvent.__eventType)
console.log(recEvent.__eventType)