no-unsafe-type-narrowing

Keywords: no unsafe type narrowing, quality, ESLint rule, JavaScript, TypeScript, SonarQube RSPEC-4326

ESLint Rule: no-unsafe-type-narrowing with LLM-optimized suggestions and auto-fix capabilities.

ESLint Rule: no-unsafe-type-narrowing with LLM-optimized suggestions and auto-fix capabilities.

Quick Summary

Rule Details

Why This Matters

Configuration

No configuration options available.

Examples

❌ Incorrect

// Example of incorrect usage

✅ Correct

// Example of correct usage

Configuration Examples

Basic Usage

// eslint.config.mjs
export default [
  {
    rules: {
      'reliability/no-unsafe-type-narrowing': 'error',
    },
  },
];

LLM-Optimized Output

🚨 no unsafe type narrowing | Description | MEDIUM
   Fix: Suggestion | Reference

Related Rules

• rule-name - Description

Further Reading

• Reference - Description

Known False Negatives

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

Dynamic Variable References

Why: Static analysis cannot trace values stored in variables or passed through function parameters.

// ❌ NOT DETECTED - Value from variable
const value = externalSource();
processValue(value); // Variable origin not tracked

Mitigation: Implement runtime validation and review code manually. Consider using TypeScript branded types for validated inputs.

Wrapped or Aliased Functions

Why: Custom wrapper functions or aliased methods are not recognized by the rule.

// ❌ NOT DETECTED - Custom wrapper
function myWrapper(data) {
  return internalApi(data); // Wrapper not analyzed
}
myWrapper(unsafeInput);

Mitigation: Apply this rule's principles to wrapper function implementations. Avoid aliasing security-sensitive functions.

Imported Values

Why: When values come from imports, the rule cannot analyze their origin or construction.

// ❌ NOT DETECTED - Value from import
import { getValue } from './helpers';
processValue(getValue()); // Cross-file not tracked

Mitigation: Ensure imported values follow the same constraints. Use TypeScript for type safety.