Array Mapping Allows Unknown Properties

[GeoMarkou]

Bug Report

🔎 Search Terms

array map properties spread operator

🕗 Version & Regression Information

Always

Please keep and fill in the line that best applies:

• This is the behavior in every version I tried, and I reviewed the FAQ for entries about Array Mapping Allows Unknown Properties

⏯ Playground Link

https://www.typescriptlang.org/play?ts=4.5.0-dev.20210910#code/JYOwLgpgTgZghgYwgAgArQM4HsTIN4BQyxyMwUGYAcnALYQBcylUoA5gNxEkYCuUIOo2ZhWITgQC+BAghyVScMAAtoDdBRzIAvPm7EyFakKYByAFJZlIUwBp9zfoPpmAyrWArTUrrPlhmHHVMLV1CEmQAOmj4FWh7CIB6ROQAYSwoKAgEMAAbAE9kaCgMjAcAMXJKGghaM0trZHMoSO9JXzkQBQRlYFyAEyyQYM0QAG0AXR1kMYsrXGa7ZFNXXgw4GwnI2jgABwAeDWwQAD4ACjOIXIhbZGAASh0T5DPwkmjI2NUoBJJk5AA6spCv0sBAMDYAipgBgipkMgB+CpVYy1JhXCBSe73IA

💻 Code

interface Person {
    firstName: string;
    surname: string;
}

const father:Person = {
    firstName: 'John',
    surname: 'Smith'
};

const son:Person = {
    ...father,
    // Correctly errors
    FirstNaem: 'John Jr.'
};

const children:Person[] = ['John Jr', 'Susan'].map<Person>((ele, i) => ({
    ...father,
    // Why doesn't this error?
    FirstNaem: ele
}))

🙁 Actual behavior

Mapping an array of Person above lets you have typos in properties and define new properties

🙂 Expected behavior

The map function at the end should have the same error as when defining const son

Type '{ FirstNaem: string; firstName: string; surname: string; }' is not assignable to type 'Person'.
Object literal may only specify known properties, but 'FirstNaem' does not exist in type 'Person'. Did you mean to write 'firstName'?(2322)

[jcalz]

Duplicate #241

[GeoMarkou]

Closing since a duplicate issue has been found