Skip to main content

no-unsafe-return

Disallow returning a value with type any from a function.

✅

Extending "plugin:@typescript-eslint/recommended-type-checked" in an ESLint configuration enables this rule.

💭

This rule requires type information to run.

The any type in TypeScript is a dangerous "escape hatch" from the type system. Using any disables many type checking rules and is generally best used only as a last resort or when prototyping code.

Despite your best intentions, the any type can sometimes leak into your codebase. Returning an an any-typed value from a function creates a potential type safety hole and source of bugs in your codebase.

This rule disallows returning any or any[] from a function.

This rule also compares generic type argument types to ensure you don't return an unsafe any in a generic position to a function that's expecting a specific type. For example, it will error if you return Set<any> from a function declared as returning Set<string>.

.eslintrc.cjs
module.exports = {
  "rules": {
    "@typescript-eslint/no-unsafe-return": "error"
  }
};
Try this rule in the playground ↗

Examples​

function foo1() {
  return 1 as any;
}
function foo2() {
  return Object.create(null);
}
const foo3 = () => {
  return 1 as any;
};
const foo4 = () => Object.create(null);

function foo5() {
  return [] as any[];
}
function foo6() {
  return [] as Array<any>;
}
function foo7() {
  return [] as readonly any[];
}
function foo8() {
  return [] as Readonly<any[]>;
}
const foo9 = () => {
  return [] as any[];
};
const foo10 = () => [] as any[];

const foo11 = (): string[] => [1, 2, 3] as any[];

// generic position examples
function assignability1(): Set<string> {
  return new Set<any>([1]);
}
type TAssign = () => Set<string>;
const assignability2: TAssign = () => new Set<any>([true]);
Open in Playground

There are cases where the rule allows to return any to unknown.

Examples of any to unknown return that are allowed:

function foo1(): unknown {
  return JSON.parse(singleObjString); // Return type for JSON.parse is any.
}

function foo2(): unknown[] {
  return [] as any[];
}
Open in Playground

Options​

This rule is not configurable.

Resources​