Assignability b/w generic keyof T and KeysOfUnion<T>

[juhort]

Ideally, keyof T should be assignable to KeysOfUnion<T> and KeysOfUnion<T> should not be assignable to keyof T.

However, currently the exactly opposite happens.

import { KeysOfUnion } from "type-fest";

// KeysOfUnion<T> should not be assignable to keyof T
type Assignability1<T, K extends keyof T> = unknown;
type Test1<T> = Assignability1<T, KeysOfUnion<T>>; // should error but doesn't

// keyof T should be assignable to KeysOfUnion<T>
type Assignability2<T, K extends KeysOfUnion<T>> = unknown;
type Test2<T> = Assignability2<T, keyof T>; // shouldn't error but does

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[som-sm]

That makes sense, let me give it a try!