Suggestion: DeepReadonly<T> type #13923
Description
TypeScript Version: 2.1.1 / nightly (2.2.0-dev.201xxxxx)
Code
It would be nice to have a shard, standard library type that allows to express deep readonly-ness (not really const, since methods are out of scope, but still...):
interface Y { a: number; }
interface X { y: Y; }
let x: Readonly<X> = {y: {a: 1}};
x.y.a = 2; // Succeeds, which is expected, but it'd be nice to have a common way to express deep readonly
type DeepReadonly<T> = {
readonly [P in keyof T]: DeepReadonly<T[P]>;
}
let deepX: DeepReadonly<X> = {y: {a: 1}};
deepX.y.a = 2; // Fails as expected!