Add eslint type assertions rule

Fixes #3359

src/browser/services/CharacterJoinerService.test.ts

@@ -270,7 +270,7 @@ function lineData(data: IPartialLineData[]): IBufferLine {
   const tline = new BufferLine(0);
   for (let i = 0; i < data.length; ++i) {
     const line = data[i][0];
-    const attr = <number>(data[i][1] || 0);
+    const attr = (data[i][1] || 0) as number;
     const offset = tline.length;
     tline.resize(tline.length + line.split('').length, CellData.fromCharData([0, '', 0, 0]));
     line.split('').map((char, idx) => tline.setCell(idx + offset, CellData.fromCharData([attr, char, 1, char.charCodeAt(0)])));

src/browser/services/SelectionService.ts

@@ -133,8 +133,8 @@ export class SelectionService extends Disposable implements ISelectionService {
     super();
 
     // Init listeners
-    this._mouseMoveListener = event => this._onMouseMove(<MouseEvent>event);
-    this._mouseUpListener = event => this._onMouseUp(<MouseEvent>event);
+    this._mouseMoveListener = event => this._onMouseMove(event as MouseEvent);
+    this._mouseUpListener = event => this._onMouseUp(event as MouseEvent);
     this._coreService.onUserInput(() => {
       if (this.hasSelection) {
         this.clearSelection();

src/browser/services/SoundService.ts

@@ -13,7 +13,7 @@ export class SoundService implements ISoundService {
 
   public static get audioContext(): AudioContext | null {
     if (!SoundService._audioContext) {
-      const audioContextCtor: typeof AudioContext = (<any>window).AudioContext || (<any>window).webkitAudioContext;
+      const audioContextCtor: typeof AudioContext = (window as any).AudioContext || (window as any).webkitAudioContext;
       if (!audioContextCtor) {
         console.warn('Web Audio API is not supported by this browser. Consider upgrading to the latest version');
         return null;