improve leaflet Util and Class typings

types/leaflet/index.d.ts

@@ -11,10 +11,12 @@ export as namespace L;
 import * as geojson from 'geojson';
 
 export class Class {
-    static extend(props: any): any/* how to return constructor of self extended type ? */;
-    static include(props: any): any /* how to return self extended type ? */;
-    static mergeOptions(props: any): any /* how to return self extended type ? */;
-    static addInitHook(initHookFn: () => void): any/* how to return self extended type ? */;
+    static extend(props: any): {new(...args: any[]): any} & typeof Class;
+    static include(props: any): any & typeof Class;
+    static mergeOptions(props: any): any & typeof Class;
+
+    static addInitHook(initHookFn: () => void): any & typeof Class;
+    static addInitHook(methodName: string, ...args: any[]): any & typeof Class;
 }
 
 export class Transformation {
@@ -1532,8 +1534,12 @@ export namespace Browser {
 }
 
 export namespace Util {
-    function extend(dest: any, src?: any): any;
-    function create(proto: any, properties?: any): any;
+    function extend<D extends object, S1 extends object = {}>(dest: D, src?: S1): D & S1;
+    function extend<D extends object, S1 extends object, S2 extends object>(dest: D, src1: S1, src2: S2): D & S1 & S2;
+    function extend<D extends object, S1 extends object, S2 extends object, S3 extends object>(dest: D, src1: S1, src2: S2, src3: S3): D & S1 & S2 & S3;
+    function extend(dest: any, ...src: any[]): any;
+
+    function create(proto: object | null, properties?: PropertyDescriptorMap): any;
     function bind(fn: () => void, ...obj: any[]): () => void;
     function stamp(obj: any): number;
     function throttle(fn: () => void, time: number, context: any): () => void;
@@ -1547,7 +1553,7 @@ export namespace Util {
     function template(str: string, data: any): string;
     function isArray(obj: any): boolean;
     function indexOf(array: any[], el: any): number;
-    function requestAnimFrame(fn: () => void, context?: any, immediate?: boolean): number;
+    function requestAnimFrame(fn: (timestamp: number) => void, context?: any, immediate?: boolean): number;
     function cancelAnimFrame(id: number): void;
 
     let lastId: number;

types/leaflet/leaflet-tests.ts

@@ -444,10 +444,13 @@ defaultIcon = new L.Icon.Default({imagePath: 'apath'});
 
 const myControlClass = L.Control.extend({});
 const myControl = new myControlClass();
+const myOtherControlClass = myControlClass.extend({});
+const myOtherControl = new myOtherControlClass();
 
 L.Control.include({});
 L.Control.mergeOptions({});
 L.Control.addInitHook(() => {});
+L.Control.addInitHook('method1', 'hello', 1);
 
 export class MyNewControl extends L.Control {
 	constructor() {
@@ -526,8 +529,35 @@ polyline = new L.Polyline(multiPolylineLatLngs);
 polyline.setLatLngs(multiPolylineLatLngs);
 const multiPolylineLatLngs2: L.LatLng[][] = polyline.getLatLngs() as L.LatLng[][];
 
-L.Util.extend({});
+const obj1 = {
+	prop1: 1,
+};
+
+const obj2 = {
+	prop2: '2',
+};
+
+const obj3 = {
+	prop3: 'three',
+};
+
+const obj4 = {
+	prop4: 'cuatro',
+};
+
+const obj5 = {
+	prop5: 'cinque',
+};
+
+const extended0: typeof obj1 = L.Util.extend(obj1);
+const extended1: typeof obj1 & typeof obj2 = L.Util.extend(obj1, obj2);
+const extended2: typeof obj1 & typeof obj2 & typeof obj3 = L.Util.extend(obj1, obj2, obj3);
+const extended3: typeof obj1 & typeof obj2 & typeof obj3 & typeof obj4 = L.Util.extend(obj1, obj2, obj3, obj4);
+const extended4: typeof obj1 & typeof obj2 & typeof obj3 & typeof obj4 & typeof obj5 = L.Util.extend(obj1, obj2, obj3, obj4, obj5);
+
 L.Util.create({});
+L.Util.create(null, {foo: {writable: true, value: 'bar'}});
+
 L.Util.bind(() => {}, {});
 L.Util.stamp({});
 L.Util.throttle(() => {}, 123, {});
@@ -546,7 +576,7 @@ L.Util.template('template', {});
 L.Util.isArray({});
 L.Util.indexOf([], {});
 L.Util.requestAnimFrame(() => {});
-L.Util.requestAnimFrame(() => {}, {});
+L.Util.requestAnimFrame(timestamp => console.log(timestamp), {});
 L.Util.requestAnimFrame(() => {}, {}, true);
 L.Util.cancelAnimFrame(1);
 L.Util.emptyImageUrl;