--- description: 'Disallow non-null assertions in the left operand of a nullish coalescing operator.' --- import Tabs from '@theme/Tabs'; import TabItem from '@theme/TabItem'; > 🛑 This file is source code, not the primary documentation location! 🛑 > > See **https://typescript-eslint.io/rules/no-non-null-asserted-nullish-coalescing** for documentation. The `??` nullish coalescing runtime operator allows providing a default value when dealing with `null` or `undefined`. Using a `!` non-null assertion type operator in the left operand of a nullish coalescing operator is redundant, and likely a sign of programmer error or confusion over the two operators. ## Examples ```ts foo! ?? bar; foo.bazz! ?? bar; foo!.bazz! ?? bar; foo()! ?? bar; let x!: string; x! ?? ''; let x: string; x = foo(); x! ?? ''; ``` ```ts foo ?? bar; foo ?? bar!; foo!.bazz ?? bar; foo!.bazz ?? bar!; foo() ?? bar; // This is considered correct code because there's no way for the user to satisfy it. let x: string; x! ?? ''; ``` ## When Not To Use It If your project's types don't yet fully describe whether certain values may be nullable, such as if you're transitioning to `strictNullChecks`, this rule might create many false reports. You might consider using [ESLint disable comments](https://eslint.org/docs/latest/use/configure/rules#using-configuration-comments-1) for those specific situations instead of completely disabling this rule. ## Further Reading - [TypeScript 3.7 Release Notes](https://www.typescriptlang.org/docs/handbook/release-notes/typescript-3-7.html) - [Nullish Coalescing Proposal](https://github.com/tc39/proposal-nullish-coalescing)