TypeScript Version: 3.9.0-dev.20200328

Search Terms:

property-will-be-overwritten-by-spread

Code

type A = {
    a?: any
}

const a: A = {};
const b = {  a: 'zzz', ...a, }; // 'a' is specified more than once, so this usage will be overwritten

Using string instead of any as the type of a property in A works as expected.

Expected behavior:

No error

Actual behavior:

'a' is specified more than once, so this usage will be overwritten.(2783)
input.ts(6, 24): This spread always overwrites this property.

Playground Link:

Using any errors - bug

https://www.typescriptlang.org/play/?ts=3.9.0-dev.20200328&ssl=6&ssc=32&pln=1&pc=1#code/C4TwDgpgBAglC8UDeAoK6oEMD8AuLAdiCgL4ooDGA9gQM7Bb5yJIkDclN9UARgsukz4A5AC9xwgDRQAdHMzT2QA

Using string no error - works as expected

https://www.typescriptlang.org/play/?ts=3.9.0-dev.20200328#code/C4TwDgpgBAglC8UDeAoK6oEMD8AuKAzsAE4CWAdgOYoC+KKAxgPblFb5yJI0DcjLbAEYJk6TPgDkALxkSANFAB0yzAt5A

Related Issues: #36779