[Bosphoramus]

The parameter only accepted { _component: { render?: () => VNode } }, but withApp() hands over Vue's App, whose _component.render is a plain Function. That mismatch made the documented setup impossible to typecheck.

Widened to a union so the old shape still works, and moved the cast inside the function (No runtime change).

Argument of type 'App<any>' is not assignable to parameter of type '{ _component: { render?: (() => VNode<RendererNode, RendererElement, { [key: string]: any; }>) | undefined; }; }'.
  Types of property '_component' are incompatible.
    Type 'ConcreteComponent<{}, any, any, ComputedOptions, MethodOptions, {}, any>' is not assignable to type '{ render?: (() => VNode<RendererNode, RendererElement, { [key: string]: any; }>) | undefined; }'.
      Value of type 'FunctionalComponent<{}, {}, any, {}>' has no properties in common with type '{ render?: (() => VNode<RendererNode, RendererElement, { [key: string]: any; }>) | undefined; }'. Did you mean to call it?