---
url: >-
  /docs/guide/usage/linter/rules/typescript/no-non-null-asserted-optional-chain.md
---

### What it does

Disallow non-null assertions after an optional chain expression.

### Why is this bad?

By design, optional chain expressions (`?.`) provide `undefined` as the expression's value, if the object being
accessed is `null` or `undefined`, instead of throwing an error. Using a non-null assertion (`!`) to assert the
result of an optional chain expression is contradictory and likely wrong, as it indicates the code is both expecting
the value to be potentially `null` or `undefined` and non-null at the same time.

In most cases, either:

1. The object is not nullable and did not need the `?.` for its property lookup
2. The non-null assertion is incorrect and introduces a type safety hole.

### Examples

Examples of **incorrect** code for this rule:

```ts
foo?.bar!;
foo?.bar()!;
```

Examples of **correct** code for this rule:

```ts
foo?.bar;
foo.bar!;
```

## How to use

## Version

This rule was added in v0.0.6.

## References