What's the difference between export interface and export default interface in typescript declaration merging?

Question

What's the difference between export interface and export default interface in declaration merging ?

I think export interface just extend, export default interface will override old interface completely.

declare module 'react-intl' {
  export interface MessageDescriptor {
    // error: ts(2717), id's type must be string
    id: 'test' | 'test2';
  }
}

if I use :

declare module 'react-intl' {
  export default interface MessageDescriptor {
    // ok
    id: 'test' | 'test2';
  }
}

Answer 1

当您导出接口时，它将仅导出类中的特定对象，但是当您导出默认接口时，它将导出所有对象并覆盖先前导出的类实例的行为。