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>
.
module.exports = {
"rules": {
"@typescript-eslint/no-unsafe-assignment": "error"
}
};
Examples
- ❌ Incorrect
- ✅ Correct
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>>>();
const x = 1,
y = 1;
const [x] = [1];
[x] = [1] as [number];
function foo(a = 1) {}
class Foo {
constructor(private a = 1) {}
}
class Foo {
private a = 1;
}
// generic position examples
const x: Set<string> = new Set<string>();
const x: Map<string, string> = new Map<string, string>();
const x: Set<string[]> = new Set<string[]>();
const x: Set<Set<Set<string>>> = new Set<Set<Set<string>>>();
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.