I have a file named `service.ts` which exposes the following code:

```
export interface SomeInterface {
  keyOne: string;
}

export class TestService<T = SomeInterface> {
  property: T;
}

```

In `index.ts` file I am using the service:

```
import { TestService } from './service';

const service = new TestService();
service.property.keyOne

```

I also created `index.d.ts` file which declare the same interface `SomeInterface` with more keys:

```
export interface SomeInterface {
  keyTwo: number;
}

```

The problem is that `service.property` only "knows" the `keyOne` property. How can I tell typescript to merge both of them?

<https://stackblitz.com/edit/typescript-cp8zmv>