Type error when trying to chain drag(...).then(...)

[p1xell0rd]

I'm trying to chain the then method after calling drag like this:

cy.get(`[data-itemId="${itemId}"]`)
  .drag(`[data-draggableId="${targetDraggableId}"]`)
  .then((success: boolean) => assert.isTrue(success));

That's pretty much what is also shown in the readme file, but I get the Typescript error TS2339: Property 'then' does not exist on type 'true'.
Looking at the type declarations for the drag function, I think it either has to return Chainable or a Promise instead of a boolean in order to allow for chaining, or am I missing something?

[Xvezda]

I added the following code to support/commands to make this work:

declare global {
  namespace Cypress {
    interface Chainable {
      drag<K extends keyof HTMLElementTagNameMap>(targetSelector: K, options?: Options): Chainable<(success: boolean) => unknown>;
      drag<E extends Node = HTMLElement>(targetSelector: string, options?: Options): Chainable<(success: boolean) => unknown>;
      drag(targetAlias: string, options?: Options): Chainable<(success: boolean) => unknown>;
    }
  }
}