父类调用子类运行报错：“ is not initialized”

父类： 
import { B } from ‘./Son’; 
 
export class A { 
  constructor() { 
  } 
 
  getInstance() { 
    if (this instanceof B) { 
    } 
  } 
} 
 
子类： 
import { A } from ‘./Father’; 
 
export class B extends A { 
} 
 
运行报错，调用栈： 
Reason:ReferenceError 
Error name:ReferenceError 
Error message:A is not initialized 
SourceCode: 
export class B extends A { 
  ^ 
  Stacktrace: 
    at func_main_0 (entry/src/main/ets/test/Son.ets:3:24)