---
url: /docs/guide/usage/linter/rules/typescript/no-inferrable-types.md
---

### What it does

Disallow explicit type declarations for variables or parameters initialized to a number, string, or boolean.

### Why is this bad?

Explicitly typing variables or parameters that are initialized to a literal value is unnecessary because TypeScript can infer the type from the value.

### Examples

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

```ts
const a: number = 5;
const b: string = "foo";
const c: boolean = true;
const fn = (a: number = 5, b: boolean = true, c: string = "foo") => {};
```

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

```ts
const a = 5;
const b = "foo";
const c = true;
const fn = (a = 5, b = true, c = "foo") => {};
```

## Configuration

This rule accepts a configuration object with the following properties:

### ignoreParameters

type: `boolean`

default: `false`

When set to `true`, ignores type annotations on function parameters.

### ignoreProperties

type: `boolean`

default: `false`

When set to `true`, ignores type annotations on class properties.

## How to use

## Version

This rule was added in v0.14.0.

## References