Typescript 使用更严格的泛型重写方法

在typescript中使用d3.js，我试图用一个返回更具体的SVGRectElement选择的方法覆盖一个返回SVGElement选择的方法

class ElementSelector {
    public getSelection(): d3.Selection<SVGElement, any, any, any> {
        return d3.select<SVGElement, any>("");
    }
}

class RectSelector extends ElementSelector {
    public getSelection(): d3.Selection<SVGRectElement, any, any, any> {
        return d3.select<SVGRectElement, any>("");
    }
}

类元素选择器{
public getSelection（）：d3.Selection{
返回d3，选择（“”）；
}
}
类RectSelector扩展了ElementSelector{
public getSelection（）：d3.Selection{
返回d3，选择（“”）；
}
}

但我得到了这个错误：

Class 'B' incorrectly extends base class 'A'.
  Types of property 'getSelection' are incompatible.
    Type '() => Selection<SVGRectElement, any, any, any>' is not assignable to type '() => Selection<SVGElement, any, any, any>'.
      Type 'Selection<SVGRectElement, any, any, any>' is not assignable to type 'Selection<SVGElement, any, any, any>'.
        Types of property 'datum' are incompatible.
          Type '{ (): any; (value: null): Selection<SVGRectElement, undefined, any, any>; <NewDatum>(value: Value...' is not assignable to type '{ (): any; (value: null): Selection<SVGElement, undefined, any, any>; <NewDatum>(value: ValueFn<S...'.
            Type 'Selection<SVGRectElement, undefined, any, any>' is not assignable to type 'Selection<SVGElement, undefined, any, any>'.
              Types of property 'on' are incompatible.
                Type '{ (typenames: string): ValueFn<SVGRectElement, undefined, void> | undefined; (typenames: string, ...' is not assignable to type '{ (typenames: string): ValueFn<SVGElement, undefined, void> | undefined; (typenames: string, list...'.
                  Type 'ValueFn<SVGRectElement, undefined, void> | undefined' is not assignable to type 'ValueFn<SVGElement, undefined, void> | undefined'.
                    Type 'ValueFn<SVGRectElement, undefined, void>' is not assignable to type 'ValueFn<SVGElement, undefined, void> | undefined'.
                      Type 'ValueFn<SVGRectElement, undefined, void>' is not assignable to type 'ValueFn<SVGElement, undefined, void>'.
                        The 'this' types of each signature are incompatible.
                          Type 'SVGElement' is not assignable to type 'SVGRectElement'.

类“B”错误地扩展了基类“A”。 属性“getSelection”的类型不兼容。 类型“（）=>Selection”不可分配给类型“（）=>Selection”。 类型“Selection”不可分配给类型“Selection”。 属性“基准”的类型不兼容。 类型“{（）：any；（值：null）：选择；（值：值…”不可分配给类型“{（）：any；（值：null）：选择；（值：ValueFn

interface Gen<T> { 
  prop: T
}

class A {
    init(param1: number): Gen<SVGElement> {
      return { prop: {} as SVGElement };
    }
}

class B extends A {
    init(param1: number): Gen<SVGRectElement> {
        return { prop: {} as SVGRectElement  };
    }
}