Can't extend mixin constructor that constructs a generic type

This applies regardless of whether or not I intersect it with some bogus type, or have a reasonable constraint. So none of the following works.

Returning a plain T

export type Constructor<T> = new (...args: any[]) => T

export interface Timestamp {
    timestamp: Date;
}

// plain old T
export function Timestamp<T, CT extends Constructor<T>>(Base: CT): Constructor<Timestamp> & Constructor<T> {
    return class extends Base {
        timestamp = new Date();
    }
}

Constructor of T with a bogus object type ({})

export type Constructor<T> = new (...args: any[]) => T

export interface Timestamp {
    timestamp: Date;
}

// Constructor of T with a bogus object type
export function Timestamp<T, CT extends Constructor<T & {}>>(Base: CT): Constructor<Timestamp> & Constructor<T> {
    return class extends Base {
        timestamp = new Date();
    }
}

Constructor of T where T is constrained to {}

export type Constructor<T> = new (...args: any[]) => T

export interface Timestamp {
    timestamp: Date;
}

export function Timestamp<T extends {}, CT extends Constructor<T>>(Base: CT): Constructor<Timestamp> & Constructor<T> {
    return class extends Base {
        timestamp = new Date();
    }
}

Constructor of T where T is constrained to object (see also #13805)

export type Constructor<T> = new (...args: any[]) => T

export interface Timestamp {
    timestamp: Date;
}

export function Timestamp<T extends object, CT extends Constructor<T>>(Base: CT): Constructor<Timestamp> & Constructor<T> {
    return class extends Base {
        timestamp = new Date();
    }
}

Start by reproducing the four generic constructor and mixin examples in the issue and inspecting the resulting type-checking errors. Trace the compiler's handling of generic construct signatures and class expressions; done means the intended generic mixin constructor pattern is accepted with the stated return type, without weakening unrelated checks.