Angular中严格类型表单联合类型收窄问题求助

我有三个核心数据相同、仅个别属性不同的表单实例，想要创建一个接收泛型参数的基表单类，以此收窄类型并移除不需要的控件，但和TypeScript僵持了数小时，差点要放弃转而使用无类型表单。

简化示例代码 #

export type FormOne = {
  name: AbstractControl<string | null>;
  email: AbstractControl<string | null>;
  age: AbstractControl<number | null>;
};

export type FormTwo = {
  name: AbstractControl<string | null>;
  email: AbstractControl<string | null>;
};

export type FormThree = {
  name: AbstractControl<string | null>;
  email: AbstractControl<string | null>;
  location: AbstractControl<string | null>;
};

export type BaseForm = FormOne | FormTwo | FormThree;

尝试定义的基类 #

@Directive()
export abstract class BaseFormComponent<T extends BaseForm> {
  private readonly _formBuilder = inject(FormBuilder);

  public readonly baseForm = this._formBuilder.group<T>({
    name: this._formBuilder.control<string | null>(''),
    email: this._formBuilder.control<string | null>(''),
    age: this._formBuilder.control<number | null>(0),
    location: this._formBuilder.control<string | null>(''),
  });
}

遇到的TS2345错误 #

TS2345: Argument of type

{
  name: FormControl<string | null>;
  email: FormControl<string | null>;
  age: FormControl<number | null>;
  location: FormControl<string | null>; 
}

is not assignable to parameter of type T

{
  name: FormControl<string | null>;
  email: FormControl<string | null>;
  age: FormControl<number | null>;
  location: FormControl<string | null>;
}

is assignable to the constraint of type T, but T could 
be instantiated with a different subtype of constraint BaseForm.

我对此感到困惑，因为BaseForm只有我定义的三个子类型，我理解联合类型BaseForm会被解析为：

{
  name: AbstractControl<string | null>;
  email: AbstractControl<string | null>;
  age?: AbstractControl<number | null>;
  location?: AbstractControl<string | null>;
}

按道理这应该允许我在抽象类中定义的基础表单结构。

最终目标组件 #

@Component({...})
export class FormTwoComponent extends BaseFormComponent<FormTwo> implements OnInit {
  public ngOnInit(): void {
    this.baseForm.removeControl('age');
    this.baseForm.removeControl('location');
  }
}

我知道上述组件在ngOnInit执行前，表单并不符合给定的T类型，可能会导致编译时问题，但现在连基类都定义不成功。恳请精通TypeScript的人解释我哪里出错了，以及是否有可行的解决方法？

内容的提问来源于stack exchange，提问作者Alex Davis