#no-invalid-void-type

#Configuration

import { defineConfig, ts } from '@rslint/core';

export default defineConfig([
  ts.configs.recommended,
  {
    rules: {
      '@typescript-eslint/no-invalid-void-type': 'error',
    },
  },
]);

#Rule Details

Disallows void type outside of generic or return types. The void type in TypeScript means a function returns nothing, and is only meaningful as a return type of functions, methods, callable signatures, construct signatures, or as a generic type argument (e.g., Promise<void>). Using void in other positions such as variable types, parameter types, or union types is typically a mistake and can lead to confusing behavior.

Examples of incorrect code for this rule:

let value: void;

function foo(arg: void) {}

type Union = string | void;

type KeyofVoid = keyof void;

let arr: void[];

let value = undefined as void;

Examples of correct code for this rule:

function foo(): void {}

type Callback = () => void;

async function bar(): Promise<void> {}

type Result = void | never;

// Callable and construct signatures
interface Callable {
  (...args: string[]): void;
}

interface Constructable {
  new (...args: string[]): void;
}

// Function overloads - void in implementation return type is valid
function f(): void;
function f(x: string): string;
function f(x?: string): string | void {
  if (x !== undefined) {
    return x;
  }
}

#Options

#allowInGenericTypeArguments

• Type: boolean | string[]
• Default: true

When true (default), allows void as a type argument in any generic type (e.g., Promise<void>, Map<string, void>).

When set to an array of strings, only allows void as a type argument in the listed generic types. Supports dotted names (e.g., ['Promise', 'Ex.Mx.Tx']).

When false, void is only valid as a direct return type.

#allowAsThisParameter

• Type: boolean
• Default: false

When true, allows void as the type of a this parameter in functions and methods.

// Valid when allowAsThisParameter is true
function f(this: void) {}
class Test {
  method(this: void) {}
}

#Original Documentation

• typescript-eslint no-invalid-void-type