Fix geometry creation in TypeScript

CHANGES.md

@@ -16,6 +16,7 @@
 - Fixed JSDoc and TypeScript type definitions for `EllipsoidTangentPlane.fromPoints`, which takes an array of `Cartesian3`, not a single instance. [#8928](https://github.com/CesiumGS/cesium/pull/8928)
 - Fixed JSDoc and TypeScript type definitions for `EntityCollection.getById` and `CompositeEntityCollection.getById`, which can both return undefined. [#8928](https://github.com/CesiumGS/cesium/pull/8928)
 - Fixed JSDoc and TypeScript type definitions for `Viewer` options parameter, which was incorrectly listed as required.
+- Fixed TypeScript type definitions to allow the creation of `GeometryInstance` instances using `XXXGeometry` classes. [#8941](https://github.com/CesiumGS/cesium/pull/8941).
 - Fixed a memory leak where some 3D Tiles requests were being unintentionally retained after the requests were cancelled. [#8843](https://github.com/CesiumGS/cesium/pull/8843)
 
 ### 1.70.0 - 2020-06-01

Source/Core/GeometryFactory.js

@@ -0,0 +1,25 @@
+import DeveloperError from "../Core/DeveloperError.js";
+
+/**
+ * Base class for all geometry creation utility classes that can be passed to {@link GeometryInstance}
+ * for asynchronous geometry creation.
+ *
+ * @constructor
+ * @class
+ * @abstract
+ */
+function GeometryFactory() {
+  DeveloperError.throwInstantiationError();
+}
+
+/**
+ * Returns a geometry.
+ *
+ * @param {GeometryFactory} geometryFactory A description of the circle.
+ * @returns {Geometry|undefined} The computed vertices and indices.
+ */
+GeometryFactory.createGeometry = function (geometryFactory) {
+  DeveloperError.throwInstantiationError();
+};
+
+export default GeometryFactory;

Source/Core/GeometryInstance.js

@@ -13,7 +13,7 @@ import Matrix4 from "./Matrix4.js";
  * @constructor
  *
  * @param {Object} options Object with the following properties:
- * @param {Geometry} options.geometry The geometry to instance.
+ * @param {Geometry|GeometryFactory} options.geometry The geometry to instance.
  * @param {Matrix4} [options.modelMatrix=Matrix4.IDENTITY] The model matrix that transforms to transform the geometry from model to world coordinates.
  * @param {Object} [options.id] A user-defined object to return when the instance is picked with {@link Scene#pick} or get/set per-instance attributes with {@link Primitive#getGeometryInstanceAttributes}.
  * @param {Object} [options.attributes] Per-instance attributes like a show or color attribute shown in the example below.

Source/Core/PlaneGeometry.js

@@ -16,7 +16,7 @@ import VertexFormat from "./VertexFormat.js";
  * @alias PlaneGeometry
  * @constructor
  *
- * @param {Object} options Object with the following properties:
+ * @param {Object} [options] Object with the following properties:
  * @param {VertexFormat} [options.vertexFormat=VertexFormat.DEFAULT] The vertex attributes to be computed.
  *
  * @example

Source/Core/SimplePolylineGeometry.js

@@ -251,7 +251,7 @@ var generateArcOptionsScratch = {
  * Computes the geometric representation of a simple polyline, including its vertices, indices, and a bounding sphere.
  *
  * @param {SimplePolylineGeometry} simplePolylineGeometry A description of the polyline.
- * @returns {Geometry} The computed vertices and indices.
+ * @returns {Geometry|undefined} The computed vertices and indices.
  */
 SimplePolylineGeometry.createGeometry = function (simplePolylineGeometry) {
   var positions = simplePolylineGeometry._positions;

Source/Core/SphereGeometry.js

@@ -110,7 +110,7 @@ SphereGeometry.unpack = function (array, startingIndex, result) {
  * Computes the geometric representation of a sphere, including its vertices, indices, and a bounding sphere.
  *
  * @param {SphereGeometry} sphereGeometry A description of the sphere.
- * @returns {Geometry} The computed vertices and indices.
+ * @returns {Geometry|undefined} The computed vertices and indices.
  */
 SphereGeometry.createGeometry = function (sphereGeometry) {
   return EllipsoidGeometry.createGeometry(sphereGeometry._ellipsoidGeometry);

Source/Core/SphereOutlineGeometry.js

@@ -110,7 +110,7 @@ SphereOutlineGeometry.unpack = function (array, startingIndex, result) {
  * Computes the geometric representation of an outline of a sphere, including its vertices, indices, and a bounding sphere.
  *
  * @param {SphereOutlineGeometry} sphereGeometry A description of the sphere outline.
- * @returns {Geometry} The computed vertices and indices.
+ * @returns {Geometry|undefined} The computed vertices and indices.
  */
 SphereOutlineGeometry.createGeometry = function (sphereGeometry) {
   return EllipsoidOutlineGeometry.createGeometry(