Playing with the case where you have an object of type T and an object of type O where the object being validated must have at least a single property of the O type which validates it.

T_with_O_validator.ts

// ------------------------------------------cut------------------------------------------------------
type TObj = { id?: number, id2?: number };

type Path<T> = PathTree<T>[keyof PathTree<T>];

type PathTree<T> = { [P in keyof T]: Required<Pick<T, P>> & Omit<T, P> };

type Check<T extends O, O> = Omit<T, keyof O> & Path<Pick<T, keyof O>>

// ------------------------------------------cut------------------------------------------------------

type Assert<A, B extends A> = any;

type successCases = [
  Assert<Check<{ a: number } & TObj, TObj>, { a: 1, id: 2}>,
  Assert<Check<{ c?: number } & TObj, TObj>, { c: 1, id2: 3, id: 1 }>,
  Assert<Check<{ d?: number } & TObj, TObj>, { id: 1 }>
]

type errorCases = [
  Assert<Check<{ b: number } & TObj, TObj>, { id2: 1 }>,
  Assert<Check<{ e: number } & TObj, TObj>, { id: 2}>,
  Assert<Check<TObj, TObj>, {}>
]