import { Injector } from '@angular/core';
/**
 * `assertInjector` extends `assertInInjectionContext` with an optional `Injector`
 * After assertion, `assertInjector` runs the `runner` function with the guaranteed `Injector`
 * whether it is the default `Injector` within the current **Injection Context**
 * or the custom `Injector` that was passed in.
 *
 * @template {() => any} Runner - Runner is a function that can return anything
 * @param {Function} fn - the Function to pass in `assertInInjectionContext`
 * @param {Injector | undefined | null} injector - the optional "custom" Injector
 * @param {Runner} runner - the runner fn
 * @returns {ReturnType<Runner>} result - returns the result of the Runner
 *
 * @example
 * ```ts
 * function injectValue(injector?: Injector) {
 *  return assertInjector(injectValue, injector, () => 'value');
 * }
 *
 * injectValue(); // string
 * ```
 */
export declare function assertInjector<Runner extends () => any>(fn: Function, injector: Injector | undefined | null, runner: Runner): ReturnType<Runner>;
/**
 * `assertInjector` extends `assertInInjectionContext` with an optional `Injector`
 * After assertion, `assertInjector` returns a guaranteed `Injector` whether it is the default `Injector`
 * within the current **Injection Context** or the custom `Injector` that was passed in.
 *
 * @param {Function} fn - the Function to pass in `assertInInjectionContext`
 * @param {Injector | undefined | null} injector - the optional "custom" Injector
 * @returns Injector
 *
 * @example
 * ```ts
 * function injectDestroy(injector?: Injector) {
 *  injector = assertInjector(injectDestroy, injector);
 *
 *  return runInInjectionContext(injector, () => {
 *    // code
 *  })
 * }
 * ```
 */
export declare function assertInjector(fn: Function, injector: Injector | undefined | null): Injector;