Spread types error TypeScript TS2698

Why This Happens

In TypeScript, typescript can't verify the spread object has the right shape. This is one of the most common TypeScript errors developers encounter. Understanding the root cause helps you fix it quickly and prevent it from recurring.

The Problem

function merge<T>(a: T, b: Partial<T>): T {
  return { ...a, ...b };
}

The Fix

function merge<T extends object>(a: T, b: Partial<T>): T {
  return { ...a, ...b };
}

Step-by-Step Fix

1. 1

   Identify the error

   Look at the error message: TS2698: Spread types only from known properties. This tells you exactly what went wrong.

2. 2

   Find the cause

   Check the stack trace to find which line of your TypeScript code triggered this error.

3. 3

   Apply the fix

   Use the corrected code pattern shown above. Test to confirm the error is resolved.