no-unsafe-type-narrowing

Report a double type assertion through unknown or any (x as unknown as T). It silences the checker exactly where it would have refused the conversion, and narrows a value nothing has checked.

This rule is part of eslint-plugin-reliability.

Quick SummaryCopy Anchor Link

Rule DetailsCopy Anchor Link

The rule reports an assertion whose operand was itself asserted to unknown or any, in every spelling TypeScript has for it:

A single assertion (raw as User, <User>raw), a widening to unknown, as const and satisfies are the checker's own business and are not reported.

ConfigurationCopy Anchor Link

With allowWithComment, the comment must say why the assertion is sound (validated, checked, type guard, safe, known, intentional, …). A comment trailing the PREVIOUS statement speaks for that statement, not this one.

ExamplesCopy Anchor Link

❌ IncorrectCopy Anchor Link

const user = raw as unknown as User;
const user = <User>(<unknown>raw);

✅ CorrectCopy Anchor Link

function isUser(value: unknown): value is User {
  return typeof value === 'object' && value !== null && 'id' in value;
}
if (isUser(raw)) use(raw);

const user = raw as User; // the checker still verifies this conversion

// With { allowWithComment: true }
// validated by the schema above
const user = raw as unknown as User;

Related RulesCopy Anchor Link

• no-missing-null-checks - Dereferences of possibly-null values

Known False NegativesCopy Anchor Link

The following patterns are not detected due to static analysis limitations:

Values the file cannot seeCopy Anchor Link

Why: a value that comes from another module, a parameter or an unresolved call carries no evidence in this file, and a rule that decides from structure stays silent rather than guess.

// ❌ NOT DETECTED - origin in another module
import { getValue } from './helpers';
processValue(getValue());

Mitigation: apply the same contract inside the helper, where the evidence is visible.

Use this rule

npm install -D oxlint-plugin-reliability

{  "jsPlugins": ["oxlint-plugin-reliability"],  "rules": {    "reliability/no-unsafe-type-narrowing": "error"  }}

import { defineConfig } from 'vite-plus';export default defineConfig({  lint: {    jsPlugins: ['oxlint-plugin-reliability'],    rules: {      'reliability/no-unsafe-type-narrowing': 'error',    },  },});