class Property 箭头函数体、初始化值、class表达式未支持

测试代码：
class ExtendedAdder extends Adder {
    x: number = 0;  **初始化值**
    y: string = '';
    // Create a copy of parent before creating our own
    private superAdd = this.add; 
    // Now create our override
    add = (b: string): string => { **箭头函数体**
        return this.superAdd(b);
    }
    public Members = class { **class表达式**

    }
}