Function call(this: Function, thisArg: any, ...argArray: any[]): any 不能用了

class A { 
  value: string; 
  constructor (value: string) { 
    this.value = value; 
  } 
 
  foo() { 
    this.fooCall(this); 
  } 
 
  fooCall(a: A) { 
    console.log('a',JSON.stringify(a)); 
    console.log(a.value); 
  } 
} 
 
let a1 = new A('1'); 
let a2 = new A('2'); 
 
a1.foo(); 
a1.fooCall(a2);