diff --git a/src/vs/workbench/api/common/extHost.api.impl.ts b/src/vs/workbench/api/common/extHost.api.impl.ts
index f8382ef8b10..3952717d220 100644
--- a/src/vs/workbench/api/common/extHost.api.impl.ts
+++ b/src/vs/workbench/api/common/extHost.api.impl.ts
@@ -475,14 +475,14 @@ export function createApiFactoryAndRegisterActors(accessor: ServicesAccessor): I
 			onDidChangeWindowState(listener, thisArg?, disposables?) {
 				return extHostWindow.onDidChangeWindowState(listener, thisArg, disposables);
 			},
-			showInformationMessage(message: string, first: vscode.MessageOptions | string | vscode.MessageItem, ...rest: Array<string | vscode.MessageItem>) {
-				return extHostMessageService.showMessage(extension, Severity.Info, message, first, rest);
+			showInformationMessage(message: string, ...rest: Array<vscode.MessageOptions | string | vscode.MessageItem>) {
+				return <Thenable<any>>extHostMessageService.showMessage(extension, Severity.Info, message, rest[0], <Array<string | vscode.MessageItem>>rest.slice(1));
 			},
-			showWarningMessage(message: string, first: vscode.MessageOptions | string | vscode.MessageItem, ...rest: Array<string | vscode.MessageItem>) {
-				return extHostMessageService.showMessage(extension, Severity.Warning, message, first, rest);
+			showWarningMessage(message: string, ...rest: Array<vscode.MessageOptions | string | vscode.MessageItem>) {
+				return <Thenable<any>>extHostMessageService.showMessage(extension, Severity.Warning, message, rest[0], <Array<string | vscode.MessageItem>>rest.slice(1));
 			},
-			showErrorMessage(message: string, first: vscode.MessageOptions | string | vscode.MessageItem, ...rest: Array<string | vscode.MessageItem>) {
-				return extHostMessageService.showMessage(extension, Severity.Error, message, first, rest);
+			showErrorMessage(message: string, ...rest: Array<vscode.MessageOptions | string | vscode.MessageItem>) {
+				return <Thenable<any>>extHostMessageService.showMessage(extension, Severity.Error, message, rest[0], <Array<string | vscode.MessageItem>>rest.slice(1));
 			},
 			showQuickPick(items: any, options?: vscode.QuickPickOptions, token?: vscode.CancellationToken): any {
 				return extHostQuickOpen.showQuickPick(items, !!extension.enableProposedApi, options, token);
@@ -533,7 +533,7 @@ export function createApiFactoryAndRegisterActors(accessor: ServicesAccessor): I
 			createOutputChannel(name: string): vscode.OutputChannel {
 				return extHostOutputService.createOutputChannel(name);
 			},
-			createWebviewPanel(viewType: string, title: string, showOptions: vscode.ViewColumn | { viewColumn: vscode.ViewColumn, preserveFocus?: boolean }, options: vscode.WebviewPanelOptions & vscode.WebviewOptions): vscode.WebviewPanel {
+			createWebviewPanel(viewType: string, title: string, showOptions: vscode.ViewColumn | { viewColumn: vscode.ViewColumn, preserveFocus?: boolean }, options?: vscode.WebviewPanelOptions & vscode.WebviewOptions): vscode.WebviewPanel {
 				return extHostWebviews.createWebviewPanel(extension, viewType, title, showOptions, options);
 			},
 			createWebviewTextEditorInset(editor: vscode.TextEditor, line: number, height: number, options?: vscode.WebviewOptions): vscode.WebviewEditorInset {
@@ -751,7 +751,12 @@ export function createApiFactoryAndRegisterActors(accessor: ServicesAccessor): I
 			},
 			openTunnel: (forward: vscode.TunnelOptions) => {
 				checkProposedApiEnabled(extension);
-				return extHostTunnelService.openTunnel(forward);
+				return extHostTunnelService.openTunnel(forward).then(value => {
+					if (!value) {
+						throw new Error('cannot open tunnel');
+					}
+					return value;
+				});
 			},
 			get tunnels() {
 				checkProposedApiEnabled(extension);
diff --git a/src/vs/workbench/api/common/extHostMessageService.ts b/src/vs/workbench/api/common/extHostMessageService.ts
index fc383d97265..ff75e2f3393 100644
--- a/src/vs/workbench/api/common/extHostMessageService.ts
+++ b/src/vs/workbench/api/common/extHostMessageService.ts
@@ -24,10 +24,11 @@ export class ExtHostMessageService {
 		this._proxy = mainContext.getProxy(MainContext.MainThreadMessageService);
 	}
 
-	showMessage(extension: IExtensionDescription, severity: Severity, message: string, optionsOrFirstItem: vscode.MessageOptions | string, rest: string[]): Promise<string | undefined>;
-	showMessage(extension: IExtensionDescription, severity: Severity, message: string, optionsOrFirstItem: vscode.MessageOptions | vscode.MessageItem, rest: vscode.MessageItem[]): Promise<vscode.MessageItem | undefined>;
-	showMessage(extension: IExtensionDescription, severity: Severity, message: string, optionsOrFirstItem: vscode.MessageOptions | vscode.MessageItem | string, rest: Array<vscode.MessageItem | string>): Promise<string | vscode.MessageItem | undefined>;
-	showMessage(extension: IExtensionDescription, severity: Severity, message: string, optionsOrFirstItem: vscode.MessageOptions | string | vscode.MessageItem, rest: Array<string | vscode.MessageItem>): Promise<string | vscode.MessageItem | undefined> {
+
+	showMessage(extension: IExtensionDescription, severity: Severity, message: string, optionsOrFirstItem: vscode.MessageOptions | string | undefined, rest: string[]): Promise<string | undefined>;
+	showMessage(extension: IExtensionDescription, severity: Severity, message: string, optionsOrFirstItem: vscode.MessageOptions | vscode.MessageItem | undefined, rest: vscode.MessageItem[]): Promise<vscode.MessageItem | undefined>;
+	showMessage(extension: IExtensionDescription, severity: Severity, message: string, optionsOrFirstItem: vscode.MessageOptions | vscode.MessageItem | string | undefined, rest: Array<vscode.MessageItem | string>): Promise<string | vscode.MessageItem | undefined>;
+	showMessage(extension: IExtensionDescription, severity: Severity, message: string, optionsOrFirstItem: vscode.MessageOptions | string | vscode.MessageItem | undefined, rest: Array<string | vscode.MessageItem>): Promise<string | vscode.MessageItem | undefined> {
 
 		const options: MainThreadMessageOptions = { extension };
 		let items: (string | vscode.MessageItem)[];
diff --git a/src/vs/workbench/contrib/quickopen/browser/gotoSymbolHandler.ts b/src/vs/workbench/contrib/quickopen/browser/gotoSymbolHandler.ts
index 16ef00ee8b7..5dfba2ef0c8 100644
--- a/src/vs/workbench/contrib/quickopen/browser/gotoSymbolHandler.ts
+++ b/src/vs/workbench/contrib/quickopen/browser/gotoSymbolHandler.ts
@@ -77,7 +77,7 @@ class OutlineModel extends QuickOpenModel {
 		const searchValuePos = searchValue.indexOf(SCOPE_PREFIX) === 0 ? 1 : 0;
 
 		// Check for match and update visibility and group label
-		this.entries.forEach((entry: SymbolEntry) => {
+		(<Array<SymbolEntry>>this.entries).forEach(entry => {
 
 			// Clear all state first
 			entry.setGroupLabel(undefined);
@@ -98,7 +98,7 @@ class OutlineModel extends QuickOpenModel {
 		});
 
 		// select comparator based on the presence of the colon-prefix
-		this.entries.sort(searchValuePos === 0
+		(<Array<SymbolEntry>>this.entries).sort(searchValuePos === 0
 			? SymbolEntry.compareByRank
 			: SymbolEntry.compareByKindAndRank
 		);
diff --git a/src/vs/workbench/contrib/themes/browser/themes.contribution.ts b/src/vs/workbench/contrib/themes/browser/themes.contribution.ts
index 0643cb30048..821c5a920d7 100644
--- a/src/vs/workbench/contrib/themes/browser/themes.contribution.ts
+++ b/src/vs/workbench/contrib/themes/browser/themes.contribution.ts
@@ -228,7 +228,7 @@ function isItem(i: QuickPickInput<ThemeItem>): i is ThemeItem {
 }
 
 function toEntries(themes: Array<IColorTheme | IFileIconTheme>, label?: string): QuickPickInput<ThemeItem>[] {
-	const toEntry = (theme: IColorTheme): ThemeItem => ({ id: theme.id, label: theme.label, description: theme.description });
+	const toEntry = (theme: IColorTheme | IFileIconTheme): ThemeItem => ({ id: theme.id, label: theme.label, description: theme.description });
 	const sorter = (t1: ThemeItem, t2: ThemeItem) => t1.label.localeCompare(t2.label);
 	let entries: QuickPickInput<ThemeItem>[] = themes.map(toEntry).sort(sorter);
 	if (entries.length > 0 && label) {