ember-source/types/stable/@ember/routing/lib/engines.d.ts

declare module '@ember/routing/lib/engines' {
  export interface EngineInfo {
    name: string;
    instanceId: number;
    mountPoint: string;
    fullName: string;
  }
  export interface EngineRouteInfo extends EngineInfo {
    localFullName: string;
    serializeMethod?: (
      model: {},
      params: string[]
    ) => {
      [key: string]: unknown | undefined;
    };
  }
}