index.d.ts export default is the interface Message, the right way is export a const value typeof interface Message.

[jovercao]

export interface Message {
  (options: MessageOptions): Promise<MessageReturn>;
  config(options: MessageOptions): MessageOptions;
  install: PluginFunction<MessageOptions>;
  alert(content: string, options: MessageOptions): Promise<MessageReturn>;
  alert(content: string, title: string, options: MessageOptions): Promise<MessageReturn>;
  confirm(content: string, options: MessageOptions): Promise<MessageReturn>;
  confirm(content: string, title: string, options: MessageOptions): Promise<MessageReturn>;
  prompt(content: string, options: MessageOptions): Promise<MessageReturn>;
  prompt(content: string, title: string, options: MessageOptions): Promise<MessageReturn>;
}

export default Message;