Strongly type `Listener`

Don't use `Function` as it allows any sort of calling pattern

src/vs/base/common/event.ts

@@ -355,7 +355,7 @@ export namespace Event {
 	}
 }
 
-type Listener = [Function, any] | Function;
+type Listener<T> = [(e: T) => void, any] | ((e: T) => void);
 
 export interface EmitterOptions {
 	onFirstListenerAdd?: Function;
@@ -466,8 +466,8 @@ export class Emitter<T> {
 	private readonly _leakageMon: LeakageMonitor | undefined;
 	private _disposed: boolean = false;
 	private _event: Event<T> | undefined;
-	private _deliveryQueue: [Listener, T][] | undefined;
-	protected _listeners: LinkedList<Listener> | undefined;
+	private _deliveryQueue: [Listener<T>, T][] | undefined;
+	protected _listeners: LinkedList<Listener<T>> | undefined;
 
 	constructor(options?: EmitterOptions) {
 		this._options = options;
@@ -541,7 +541,7 @@ export class Emitter<T> {
 	 * To be kept private to fire an event to
 	 * subscribers
 	 */
-	fire(event: T): any {
+	fire(event: T): void {
 		if (this._listeners) {
 			// put all [listener,event]-pairs into delivery queue
 			// then emit all event. an inner/nested event might be
@@ -590,7 +590,7 @@ export interface IWaitUntil {
 
 export class AsyncEmitter<T extends IWaitUntil> extends Emitter<T> {
 
-	private _asyncDeliveryQueue: [Listener, T, Promise<any>[]][];
+	private _asyncDeliveryQueue: [Listener<T>, T, Promise<any>[]][];
 
 	async fireAsync(eventFn: (thenables: Promise<any>[], listener: Function) => T): Promise<void> {
 		if (!this._listeners) {

src/vs/workbench/browser/parts/quickinput/quickInput.ts

@@ -252,14 +252,20 @@ class QuickInput implements IQuickInput {
 			this.ui.leftActionBar.clear();
 			const leftButtons = this.buttons.filter(button => button === backButton);
 			this.ui.leftActionBar.push(leftButtons.map((button, index) => {
-				const action = new Action(`id-${index}`, '', button.iconClass || getIconClass(button.iconPath), true, () => this.onDidTriggerButtonEmitter.fire(button));
+				const action = new Action(`id-${index}`, '', button.iconClass || getIconClass(button.iconPath), true, () => {
+					this.onDidTriggerButtonEmitter.fire(button);
+					return Promise.resolve(null);
+				});
 				action.tooltip = button.tooltip;
 				return action;
 			}), { icon: true, label: false });
 			this.ui.rightActionBar.clear();
 			const rightButtons = this.buttons.filter(button => button !== backButton);
 			this.ui.rightActionBar.push(rightButtons.map((button, index) => {
-				const action = new Action(`id-${index}`, '', button.iconClass || getIconClass(button.iconPath), true, () => this.onDidTriggerButtonEmitter.fire(button));
+				const action = new Action(`id-${index}`, '', button.iconClass || getIconClass(button.iconPath), true, () => {
+					this.onDidTriggerButtonEmitter.fire(button);
+					return Promise.resolve(null);
+				});
 				action.tooltip = button.tooltip;
 				return action;
 			}), { icon: true, label: false });

src/vs/workbench/services/search/test/node/rawSearchService.test.ts

@@ -143,7 +143,7 @@ suite('RawSearchService', () => {
 		const service = new RawSearchService();
 
 		function fileSearch(config: IFileQuery, batchSize: number): Event<ISerializedSearchProgressItem | ISerializedSearchComplete> {
-			let promise: CancelablePromise<ISerializedSearchSuccess>;
+			let promise: CancelablePromise<ISerializedSearchSuccess | void>;
 
 			const emitter = new Emitter<ISerializedSearchProgressItem | ISerializedSearchComplete>({
 				onFirstListenerAdd: () => {