The revised `solution.ts` file with types added is shown below:

```typescript 
/** An append-only log of timestamped events. */
export class EventLog {
  #events: Event[] = [];

  /** Append one event. */
  record(event: Event): void {
    this.#events.push(event);
  }

  /** Every event at or after the given timestamp, in insertion order. */
  since(timestamp: number): Event[] {
    // If you want to return copies of events rather than references, use this line instead.
    // return this.#events.filter((event) => event.timestamp >= timestamp).map(e => ({...e}));
 
    return this.#events.filter((event: Event) => event.timestamp >= timestamp);
  }
}

export interface Event { 
  name: string; 
  timestamp: number; 
}
```