attempt-to-enforce-inferred-redirects.ts

export {};

type RouteConfig = {
  pathname: string;
  redirect?: {
    pathname: string;
  };
};

type ExtractPathnames<Routes extends Record<string, RouteConfig>> = {
  [K in keyof Routes]: Routes[K]['pathname'];
}[keyof Routes];

type ValidateRedirects<
  Routes extends Record<string, RouteConfig>,
  AllPathnames
> = {
  [K in keyof Routes]: Routes[K] extends {
    redirect: { pathname: string };
  }
    ? Routes[K] extends {
        redirect: { pathname: infer P };
      }
      ? P extends AllPathnames
        ? Routes[K]
        : never
      : never
    : Routes[K];
};

function createRoutes<Routes extends Record<string, RouteConfig>>(
  routes: ValidateRedirects<Routes, ExtractPathnames<Routes>>
): Routes {
  return routes;
}

function getRoutePaths<Routes extends Record<string, RouteConfig>>(
  routes: Routes
): ExtractPathnames<Routes>[] {
  return [];
}

// Usage
const RouteHashMap = createRoutes({
  a: {
    pathname: '/a',
    redirect: {
      pathname: 'f', // <<<< SHOULD FAIL. BUT DOES NOT T_T
    },
  },
  b: {
    pathname: '/b',
  },
  c: {
    pathname: '/a/b/c',
  },
  old_c: {
    pathname: '/c',
  },
  d: {
    pathname: '/d',
  },
} as const);

const RoutePathnames = getRoutePaths(RouteHashMap);