@antfu/eslint-define-config/src/utility-types.d.ts

Provide a defineConfig function for .eslintrc.js files

/**
 * A literal type that supports custom further strings but preserves autocompletion in IDEs.
 *
 * @see [copied from issue](https://github.com/microsoft/TypeScript/issues/29729#issuecomment-471566609)
 */
export type LiteralUnion<Union extends Base, Base = string> =
  | Union
  | (Base & { zz_IGNORE_ME?: never });