因此，在工作中，我们使用这些类型来创建我们的几何基础：

export type GeoJSON = Geometry | Feature;

export type GeoJsonTypes = GeoJSON['type'];

export interface GeoJsonObject { type: GeoJsonTypes; }

export interface Point extends GeoJsonObject {
   type: 'Point';
   coordinates: number[];
 }

export interface MultiPoint extends GeoJsonObject {
   type: "MultiPoint",
   coordinates: number[][];
 }

export type Geometry =
 | Point
 | MultiPoint

export interface Feature<G extends Geometry = Geometry>
  extends GeoJsonObject {
  type: 'Feature';
  geometry: G;
}

问题是我们最终不得不为每个几何体创建单独的typeguard：

export const isPointGeometry = (g: Geometry): g is Point => {
  return (g as Point).type === 'Point';
};

我试着创建一个通用的typeguard：

export function isGeometry<T extends Geometry, G extends GeoJsonObject['type']>(feature: T, geometry: G): feature is T {
  return feature && feature && feature.type === geometry;
}

但是没有用。因为我仍然有问题？有人有主意吗？

export function coordinatesFor(f: Feature<Point | MultiPoint>) {
  if (isGeometry(f.geometry, 'Point')) {
   return f.geometry.coordinates ?? []; // Expected Feature<Point> but got Feature<Point | MultiPoint>
  }
  return [];
 }