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Disallows assigning any to variables and properties (no-unsafe-assignment)

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. Operations on the variable will not be checked at all by TypeScript, so it creates a potential safety hole, and source of bugs in your codebase.

Rule Details

This rule disallows assigning any to a variable, and assigning any[] to an array destructuring. This rule also compares the assigned type to the variable's type to ensure you don't assign 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>.

Examples of code for this rule:

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>;

Attributes

  • ✅ Recommended
  • 🔧 Fixable
  • 💭 Requires type information