close
Rslint

    no-unnecessary-type-assertion

    Configuration

    rslint.config.ts
    import { defineConfig, ts } from '@rslint/core';

export default defineConfig([
  ts.configs.recommended,
  {
    rules: {
      '@typescript-eslint/no-unnecessary-type-assertion': 'error',
    },
  },
]);

    Rule Details

    Disallow type assertions that do not change the type of an expression.

    Type assertions (as expressions, angle-bracket syntax, and non-null assertions !) that don't actually change the type of an expression are unnecessary and add noise to the code. This includes non-null assertions on values that are already non-nullable.

    Examples of incorrect code for this rule:

    const foo = 3;
const bar = foo!; // foo is already non-nullable

const str = 'hello' as string; // already a string

declare const value: number;
const num = value as number; // already a number

    Examples of correct code for this rule:

    const foo: number | undefined = getValue();
const bar = foo!; // non-null assertion is meaningful

const value = someUnknown as string; // type narrowing

const x = 3 as const; // const assertions are allowed

    Original Documentation