ts
type IfEquals =
(() => T extends X ? 1 : 2) extends
(() => T extends Y ? 1 : 2) ? A : B;
type WritableKeys = {
[P in keyof T]-?: IfEquals<{ [Q in P]: T[P] }, { -readonly [Q in P]: T[P] }, P>
}[keyof T];
type ReadonlyKeys = {
[P in keyof T]-?: IfEquals<{ [Q in P]: T[P] }, { -readonly [Q in P]: T[P] }, never, P>
}[keyof T];