TS 3.7：optionalChaining nullishCoalescing是否不适用于联合类型？

Question

我希望新的TypeScript 3.7功能可以支持以下情况：

export interface Foo {
  aaa: string;
  bbb: string;
  ccc: string;
}

export interface Bar {
  ddd: string;
  eee: string;
  fff: string;
}

type Data = Foo | Bar;

const doSomething = (data: Data) => {
  const optionalChaining = data?.aaa //error
  const nullishCoalescing = data.bbb ?? "default"; //error

  if ("ccc" in data) {
    //OK this works
  }
}

除了后者在较早的ts版本中也起作用之外，是否还有其他方法可以处理此问题？ ts-playground：http://www.typescriptlang.org/play/?ts=3.7-Beta#code/KYDwDg9gTgLgBASwHY2FAZgQwMbDgMQgjgG8BYAKDjk1oC44BnGKZAcwG5LqAjPh5qySducbOIEt2XCgF9KlUJFiIUaLLjgAhTFFKiAJkclCRVOMEsnpo9HevCZ8ipRgBPMHgAimGJjgAvAREcAA+2roylNgQSMxwBhAAyhAAtsAwABbsgXAAFAa+mAw+fgCUgQB8+uYxcfAQYDAIsZgANgDCmZjIOUGFfgD8AHS0mKJ18UgArm1tCIyZHRDtwIzYfQlFw3w8cIODcABEBsBYszBHUeYI6PlH4thHqlvlNdTUAPSfAPIA0nAsgs4AB3aAAa0YomcziAA