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no-unsafe-assignment

Disallow assigning a value with type any to variables and properties.

🧠

Extending "plugin:@typescript-eslint/recommended-requiring-type-checking" 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. Assigning an any typed value to a variable can be hard to pick up on, particularly if it leaks in from an external library.

This rule disallows assigning any to a variable, and assigning any[] to an array destructuring.

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

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

Examples​

const x = 1 as any,
  y = 1 as any;
const [x] = 1 as any;
const [x] = [] as any[];
const [x] = [1 as any];
[x] = [1] as [any];

function foo(a = 1 as any) {}
class Foo {
  constructor(private a = 1 as any) {}
}
class Foo {
  private a = 1 as any;
}

// generic position examples
const x: Set<string> = new Set<any>();
const x: Map<string, string> = new Map<string, any>();
const x: Set<string[]> = new Set<any[]>();
const x: Set<Set<Set<string>>> = new Set<Set<Set<any>>>();

There are cases where the rule allows assignment of any to unknown.

Example of any to unknown assignment that are allowed:

const x: unknown = y as any;
const x: unknown[] = y as any[];
const x: Set<unknown> = y as Set<any>;

Options​

This rule is not configurable.

Resources​