Why does the compiler complain about this Partial

Question

I might be missing something here, but I don't understand why the following code isn't valid:

interface TestType {
  id: string;
}

interface TestConstraint<T extends TestType> {
  readonly id: string;
  readonly rawData: Partial<T>
}

class GenericClass<T extends TestType> implements TestConstraint<T> {
  readonly id: string;

  constructor(
    rawData: T
  ) {
    this.id = rawData.id;
  }

  get rawData(): Partial<T> {
    return {
        id: this.id,
    };
    // return {
    //     id: this.id,
    // } as Partial<T>;
  }
}

The compiler is returning an error:

Type '{ id: string; }' is not assignable to type 'Partial<T>'.(2322)

That seems weird because that's roughly the definition of the TestType.

Playground with the code above.