type ExpectedType = Array<{ name: number, gender?: string }>
function go1(p: ExpectedType) {
}
function f() {
const a = [{name: 1, age: 2}]
go1(a) // no error shown
go1([{name: 1, age: 2}]) // error displayed 'Object literal may only specify known...'
go1(['no matter'].map(n => ({name: 1, age: 2}))) // no issue arises
}
The TypeScript code outlined above brings up an interesting inquiry - why do the last three lines appear to be identical? How come the first line is accepted without issues, while the second line raises an error and the third line does not?
To see it in action on the TypeScript playground, visit: playground