#no-unnecessary-type-assertion

#Configuration

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

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

#Rule Details

This rule reports unnecessary assertions, including as, angle-bracket assertions, and non-null assertions (!).

Examples of incorrect code for this rule:

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

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;

#Options

#Differences from upstream

Rslint keeps assertions that your code relies on. This helps avoid new type errors, lost type information, or changes in behavior after running --fix.

Some assertions are reported without an automatic fix, so their diagnostics remain after --fix. This includes certain assertions split across lines with comments. The rule leaves these assertions in place to preserve your program's behavior.

#Original Documentation

• typescript-eslint: no-unnecessary-type-assertion
• Source code