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# no-extra-non-null-assertion

[Added in v0.2.1](https://github.com/web-infra-dev/rslint/releases/tag/v0.2.1)
## Configuration

| Preset                              | Configured Value |
| ----------------------------------- | ---------------- |
| ✅ ts.configs.recommended            | `"error"`        |
| ✅ ts.configs.recommendedTypeChecked | `"error"`        |
| ✅ ts.configs.strict                 | `"error"`        |
| ✅ ts.configs.strictTypeChecked      | `"error"`        |


```ts title=rslint.config.ts
import { defineConfig, ts } from '@rslint/core';

export default defineConfig([
  ts.configs.recommended,
  {
    rules: {
      '@typescript-eslint/no-extra-non-null-assertion': 'error',
    },
  },
]);
```

## Rule Details

Disallow extra non-null assertions.

The `!` non-null assertion operator in TypeScript is used to assert that a value's type does not include `null` or `undefined`. Using the operator any more than once on a single value does nothing.

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

```typescript
const bar = foo!!.bar;
function foo(bar?: { n: number }) {
  return bar!?.n;
}
```

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

```typescript
const bar = foo!.bar;
function foo(bar?: { n: number }) {
  return bar?.n;
}
```

## Original Documentation

- [typescript-eslint: no-extra-non-null-assertion](https://typescript-eslint.io/rules/no-extra-non-null-assertion)
- [Source code](https://github.com/typescript-eslint/typescript-eslint/blob/v8.67.0/packages/eslint-plugin/src/rules/no-extra-non-null-assertion.ts)