Missing class name when use decorator

[Brooooooklyn]

const bar = (target: any, name: any, value: any) => {
  const parentName = target.constructor.name
  console.log(parentName)
}
class a {
  @bar
  public foo() {
  }
}

It works. But

const bar = (target: any, name: any, value: any) => {
  const parentName = target.constructor.name
  console.log(parentName)
 // it would be an empty string here!!!!!!!!
}
const log = (target: any) => {}

@log
class a {
  @bar
  public foo() {
  }
}

these code is ok when compile target was ES5, but missing class name when target was ES6

[mhegazy]

duplicate of #5386