typescript : Mixin vs Generic class

In below example, How can i serve same purpose using Mixin while GenericClass is working expected.

import "reflect-metadata";
import Knex, { Knex as KnexSpace } from "knex";
export const knex = Knex({
  client: "pg",
})
type Constructor<T = {}> = new (...args: any[]) => T;
const tableMetaName = Symbol("table");

export function Mixin<TBase extends Constructor>(Base: TBase) {
  return class extends Base {
    query = knex.table<KnexSpace.CompositeTableType<TBase>>(
      Reflect.getMetadata(tableMetaName, Base).tableName
      );
  };
}

export class GenericClass<TBase extends {}> {
  query = knex.table<KnexSpace.CompositeTableType<TBase>>(
    Reflect.getMetadata(tableMetaName, this.constructor).tableName
  );
}




class User {
  id: number;
  firstname?: string;
}

const userModal = Mixin(User);
new userModal().query.insert({ id: 1 }); // Error Argument of type '{ id: number; }' is not assignable to parameter of type 'typeof User | readonly (typeof User)[]'.

new GenericClass<User>().query.insert({ id: 1 });

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