angular-docs-cn/packages/core/src/util/closure.ts

/**
 * @license
 * Copyright Google Inc. All Rights Reserved.
 *
 * Use of this source code is governed by an MIT-style license that can be
 * found in the LICENSE file at https://angular.io/license
 */

/**
 * Convince closure compiler that the wrapped function has no side-effects.
 *
 * Closure compiler always assumes that `toString` has no side-effects. We use this quirk to
 * allow us to execute a function but have closure compiler mark the call as no-side-effects.
 * It is important that the return value for the `noSideEffects` function be assigned
 * to something which is retained otherwise the call to `noSideEffects` will be removed by closure
 * compiler.
 */
export function noSideEffects<T>(fn: () => T): T {
  return {toString: fn}.toString() as unknown as T;
}