# Source: https://oxc.rs/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

To **enable** this rule using the config file or in the CLI, you can use:

::: code-group

```json [Config (.oxlintrc.json)]
{
  "rules": {
    "typescript/no-inferrable-types": "error"
  }
}
```

```bash [CLI]
oxlint --deny typescript/no-inferrable-types
```

:::

## References

* Rule Source