<!-- 🚨 STOP 🚨 𝗦𝗧𝗢𝗣 🚨 𝑺𝑻𝑶𝑷 🚨 Half of all issues filed here are duplicates, answered in the FAQ, or not appropriate for the bug tracker. Even if you think you've found a *bug*, please read the FAQ first, especially the Common "Bugs" That Aren't Bugs section! Please help us by doing the following steps before logging an issue: * Search: https://github.com/Microsoft/TypeScript/search?type=Issues * Read the FAQ: https://github.com/Microsoft/TypeScript/wiki/FAQ Please fill in the *entire* template below. --> <!-- Please try to reproduce the issue with the latest published version. It may have already been fixed. For npm: `typescript@next` This is also the 'Nightly' version in the playground: http://www.typescriptlang.org/play/?ts=Nightly --> **TypeScript Version:** 3.9.2 <!-- Search terms you tried before logging this (so others can find this issue more easily) --> **Search Terms:** * property-will-be-overwritten-by-spread * 2783 * is specified more than once, so this usage will be overwritten * spread **Code** ```ts import { Select } from '@material-ui/core'; import React from 'react'; export function Repro({ SelectProps = {} }: { SelectProps?: Partial<React.ComponentProps<typeof Select>> }) { return ( <Select value={'test'} {...SelectProps} /> ); } ``` **Expected behavior:** No error, as `value` in `SelectProps` is optional and `SelectProps` even defaults to an empty object. **Actual behavior:** > 'value' is specified more than once, so this usage will be overwritten.ts(2783) > Repro.tsx(7, 32): This spread always overwrites this property. **Playground Link:** none, as the playground does not seem to load the material-ui types