fix(typescript): fix reduce return type

package.json

@@ -16,6 +16,7 @@
   "types": "lib/index.d.ts",
   "scripts": {
     "test": "mocha test/",
+    "prebuild": "rimraf lib",
     "build": "cross-env NODE_ENV=production tsc -p .",
     "watch": "tsc -p . --watch",
     "prepublish": "npm run --if-present build"
@@ -42,6 +43,7 @@
     "espower-typescript": "^8.0.0",
     "mocha": "^3.2.0",
     "power-assert": "^1.4.2",
+    "rimraf": "^2.6.1",
     "typescript": "^2.2.2"
   }
 }

src/ReduceState.ts

@@ -28,7 +28,7 @@ export class ReduceState {
      * @param {Object} payload
      * @returns {ReduceState}
      */
-    reduce(payload: Payload): ReduceState {
+    reduce<T extends ReduceState>(payload: Payload): T | this {
         switch (payload.type) {
             default:
                 return this;

src/ReduceStore.ts

@@ -3,14 +3,11 @@
 const assert = require("assert");
 import { Store, Payload } from "almin";
 import { ReduceState } from "./ReduceState";
-export class ReduceStore extends Store {
-    state: ReduceState | null;
+export class ReduceStore<T extends ReduceState> extends Store {
+    state: T | null;
 
     constructor() {
         super();
-        /**
-         * @type {ReduceState}
-         **/
         this.state = null;
         // Automatically handling onDispatch
         this.onDispatch(this._onDispatch.bind(this));
@@ -21,7 +18,7 @@ export class ReduceStore extends Store {
      * If `newState` is the same with `tis.state`, don't set.
      * @param {ReduceState} newState
      */
-    setState(newState: ReduceState): void {
+    setState(newState: T): void {
         if (process.env.NODE_ENV !== "production") {
             assert(this.state !== null, "this.state is null, should be set to this.state in constructor.");
             assert(newState instanceof this.state!.constructor, `newState should be instanceof exist this.state.constructor.
@@ -46,6 +43,6 @@ this.state.constructor: ${this.state!.constructor}
             assert(this.state !== null, "this.state is null, should be set to this.state in constructor.");
             assert(payload !== undefined, `payload is undefined: ${payload}`);
         }
-        this.setState(this.state!.reduce(payload));
+        this.setState(this.state!.reduce<T>(payload));
     }
 }