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no-unsafe-call

Disallow calling a value with type any.

✅

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. Calling an any-typed value as a function creates a potential type safety hole and source of bugs in your codebase.

This rule disallows calling any value that is typed as any.

eslint.config.mjs
export default tseslint.config({
  rules: {
    "@typescript-eslint/no-unsafe-call": "error"
  }
});

Try this rule in the playground ↗

Examples​

declare const anyVar: any;
declare const nestedAny: { prop: any };

anyVar();
anyVar.a.b();

nestedAny.prop();
nestedAny.prop['a']();

new anyVar();
new nestedAny.prop();

anyVar`foo`;
nestedAny.prop`foo`;
Open in Playground

The Unsafe Function Type​

The Function type is behaves almost identically to any when called, so this rule also disallows calling values of type Function.

const f: Function = () => {};
f();
Open in Playground

Note that whereas no-unsafe-function-type helps prevent the creation of Function types, this rule helps prevent the unsafe use of Function types, which may creep into your codebase without explicitly referencing the Function type at all. See, for example, the following code:

function callUnsafe(maybeFunction: unknown): string {
  if (typeof maybeFunction === 'function') {
    // TypeScript allows this, but it's completely unsound.
    return maybeFunction('call', 'with', 'any', 'args');
  }
  // etc
}

In this sort of situation, beware that there is no way to guarantee with runtime checks that a value is safe to call. If you really want to call a value whose type you don't know, your best best is to use a try/catch and suppress any TypeScript or linter errors that get in your way.

function callSafe(maybeFunction: unknown): void {
  try {
    // intentionally unsound type assertion
    (maybeFunction as () => unknown)();
  } catch (e) {
    console.error(
      'Function either could not be called or threw an error when called: ',
      e,
    );
  }
}

Options​

This rule is not configurable.

When Not To Use It​

If your codebase has many existing anys or areas of unsafe code, it may be difficult to enable this rule. It may be easier to skip the no-unsafe-* rules pending increasing type safety in unsafe areas of your project. You might consider using ESLint disable comments for those specific situations instead of completely disabling this rule.

Type checked lint rules are more powerful than traditional lint rules, but also require configuring type checked linting.

See Troubleshooting > Linting with Type Information > Performance if you experience performance degradations after enabling type checked rules.

Resources​