Use type template for the source type of layers

src/ol/layer/BaseTile.js

@@ -39,6 +39,7 @@ import {assign} from '../obj.js';
  * property on the layer object; for example, setting `title: 'My Title'` in the
  * options means that `title` is observable, and has get/set accessors.
  *
+ * @extends {Layer<import("../source/Tile.js").default>}
  * @api
  */
 class BaseTileLayer extends Layer {
@@ -102,13 +103,4 @@ class BaseTileLayer extends Layer {
 }
 
 
-/**
- * Return the associated {@link module:ol/source/Tile tilesource} of the layer.
- * @function
- * @return {import("../source/Tile.js").default} Source.
- * @api
- */
-BaseTileLayer.prototype.getSource;
-
-
 export default BaseTileLayer;