diff --git a/src/vs/base/browser/ui/grid/gridview.ts b/src/vs/base/browser/ui/grid/gridview.ts
index 26e01ee7089..1c4944ce539 100644
--- a/src/vs/base/browser/ui/grid/gridview.ts
+++ b/src/vs/base/browser/ui/grid/gridview.ts
@@ -188,12 +188,12 @@ class BranchNode implements ISplitView, IDisposable {
 		return this.orientation === Orientation.HORIZONTAL ? this.maximumSize : this.maximumOrthogonalSize;
 	}
 
-	private _onDidChange = new Emitter<number | undefined>();
+	private readonly _onDidChange = new Emitter<number | undefined>();
 	readonly onDidChange: Event<number | undefined> = this._onDidChange.event;
 
 	private childrenChangeDisposable: IDisposable = Disposable.None;
 
-	private _onDidSashReset = new Emitter<number[]>();
+	private readonly _onDidSashReset = new Emitter<number[]>();
 	readonly onDidSashReset: Event<number[]> = this._onDidSashReset.event;
 	private splitviewSashResetDisposable: IDisposable = Disposable.None;
 	private childrenSashResetDisposable: IDisposable = Disposable.None;
@@ -539,7 +539,7 @@ class LeafNode implements ISplitView, IDisposable {
 		this._onDidSetLinkedNode.fire(undefined);
 	}
 
-	private _onDidSetLinkedNode = new Emitter<number | undefined>();
+	private readonly _onDidSetLinkedNode = new Emitter<number | undefined>();
 	private _onDidViewChange: Event<number | undefined>;
 	readonly onDidChange: Event<number | undefined>;
 
diff --git a/src/vs/base/browser/ui/list/listView.ts b/src/vs/base/browser/ui/list/listView.ts
index 284a66f41b9..0d2404422c8 100644
--- a/src/vs/base/browser/ui/list/listView.ts
+++ b/src/vs/base/browser/ui/list/listView.ts
@@ -190,7 +190,7 @@ export class ListView<T> implements ISpliceable<T>, IDisposable {
 
 	private readonly disposables: DisposableStore = new DisposableStore();
 
-	private _onDidChangeContentHeight = new Emitter<number>();
+	private readonly _onDidChangeContentHeight = new Emitter<number>();
 	readonly onDidChangeContentHeight: Event<number> = Event.latch(this._onDidChangeContentHeight.event);
 	get contentHeight(): number { return this.rangeMap.size; }
 
diff --git a/src/vs/base/browser/ui/list/listWidget.ts b/src/vs/base/browser/ui/list/listWidget.ts
index a969eab5f45..51d1b8b0732 100644
--- a/src/vs/base/browser/ui/list/listWidget.ts
+++ b/src/vs/base/browser/ui/list/listWidget.ts
@@ -110,7 +110,7 @@ class Trait<T> implements ISpliceable<boolean>, IDisposable {
 	private indexes: number[] = [];
 	private sortedIndexes: number[] = [];
 
-	private _onChange = new Emitter<ITraitChangeEvent>();
+	private readonly _onChange = new Emitter<ITraitChangeEvent>();
 	readonly onChange: Event<ITraitChangeEvent> = this._onChange.event;
 
 	get trait(): string { return this._trait; }
@@ -176,7 +176,7 @@ class Trait<T> implements ISpliceable<boolean>, IDisposable {
 	}
 
 	dispose() {
-		this._onChange = dispose(this._onChange);
+		dispose(this._onChange);
 	}
 }
 
@@ -1111,10 +1111,10 @@ export class List<T> implements ISpliceable<T>, IDisposable {
 		return Event.map(this.eventBufferer.wrapEvent(this.selection.onChange), e => this.toListEvent(e));
 	}
 
-	private _onDidOpen = new Emitter<IListEvent<T>>();
+	private readonly _onDidOpen = new Emitter<IListEvent<T>>();
 	readonly onDidOpen: Event<IListEvent<T>> = this._onDidOpen.event;
 
-	private _onDidPin = new Emitter<IListEvent<T>>();
+	private readonly _onDidPin = new Emitter<IListEvent<T>>();
 	readonly onDidPin: Event<IListEvent<T>> = this._onDidPin.event;
 
 	get domId(): string { return this.view.domId; }
@@ -1168,7 +1168,7 @@ export class List<T> implements ISpliceable<T>, IDisposable {
 	readonly onDidFocus: Event<void>;
 	readonly onDidBlur: Event<void>;
 
-	private _onDidDispose = new Emitter<void>();
+	private readonly _onDidDispose = new Emitter<void>();
 	readonly onDidDispose: Event<void> = this._onDidDispose.event;
 
 	constructor(
diff --git a/src/vs/base/browser/ui/tree/abstractTree.ts b/src/vs/base/browser/ui/tree/abstractTree.ts
index 5f6a4fc8d69..41018dd1e50 100644
--- a/src/vs/base/browser/ui/tree/abstractTree.ts
+++ b/src/vs/base/browser/ui/tree/abstractTree.ts
@@ -567,7 +567,7 @@ class TypeFilterController<T, TFilterData> implements IDisposable {
 	private _empty: boolean = false;
 	get empty(): boolean { return this._empty; }
 
-	private _onDidChangeEmptyState = new Emitter<boolean>();
+	private readonly _onDidChangeEmptyState = new Emitter<boolean>();
 	readonly onDidChangeEmptyState: Event<boolean> = Event.latch(this._onDidChangeEmptyState.event);
 
 	private positionClassName = 'ne';
@@ -581,7 +581,7 @@ class TypeFilterController<T, TFilterData> implements IDisposable {
 	private automaticKeyboardNavigation = true;
 	private triggered = false;
 
-	private _onDidChangePattern = new Emitter<string>();
+	private readonly _onDidChangePattern = new Emitter<string>();
 	readonly onDidChangePattern = this._onDidChangePattern.event;
 
 	private enabledDisposables: IDisposable[] = [];
@@ -934,7 +934,7 @@ class Trait<T> {
 	private nodes: ITreeNode<T, any>[] = [];
 	private elements: T[] | undefined;
 
-	private _onDidChange = new Emitter<ITreeEvent<T>>();
+	private readonly _onDidChange = new Emitter<ITreeEvent<T>>();
 	readonly onDidChange = this._onDidChange.event;
 
 	private _nodeSet: Set<ITreeNode<T, any>> | undefined;
@@ -1204,7 +1204,7 @@ export abstract class AbstractTree<T, TFilterData, TRef> implements IDisposable
 	get onDidChangeCollapseState(): Event<ICollapseStateChangeEvent<T, TFilterData>> { return this.model.onDidChangeCollapseState; }
 	get onDidChangeRenderNodeCount(): Event<ITreeNode<T, TFilterData>> { return this.model.onDidChangeRenderNodeCount; }
 
-	private _onWillRefilter = new Emitter<void>();
+	private readonly _onWillRefilter = new Emitter<void>();
 	readonly onWillRefilter: Event<void> = this._onWillRefilter.event;
 
 	get filterOnType(): boolean { return !!this._options.filterOnType; }
@@ -1213,7 +1213,7 @@ export abstract class AbstractTree<T, TFilterData, TRef> implements IDisposable
 	get openOnSingleClick(): boolean { return typeof this._options.openOnSingleClick === 'undefined' ? true : this._options.openOnSingleClick; }
 	get expandOnlyOnTwistieClick(): boolean | ((e: T) => boolean) { return typeof this._options.expandOnlyOnTwistieClick === 'undefined' ? false : this._options.expandOnlyOnTwistieClick; }
 
-	private _onDidUpdateOptions = new Emitter<IAbstractTreeOptions<T, TFilterData>>();
+	private readonly _onDidUpdateOptions = new Emitter<IAbstractTreeOptions<T, TFilterData>>();
 	readonly onDidUpdateOptions: Event<IAbstractTreeOptions<T, TFilterData>> = this._onDidUpdateOptions.event;
 
 	get onDidDispose(): Event<void> { return this.view.onDidDispose; }
diff --git a/src/vs/base/browser/ui/tree/indexTreeModel.ts b/src/vs/base/browser/ui/tree/indexTreeModel.ts
index 182caa98612..8616d00e8cd 100644
--- a/src/vs/base/browser/ui/tree/indexTreeModel.ts
+++ b/src/vs/base/browser/ui/tree/indexTreeModel.ts
@@ -62,17 +62,17 @@ export class IndexTreeModel<T extends Exclude<any, undefined>, TFilterData = voi
 	private root: IIndexTreeNode<T, TFilterData>;
 	private eventBufferer = new EventBufferer();
 
-	private _onDidChangeCollapseState = new Emitter<ICollapseStateChangeEvent<T, TFilterData>>();
+	private readonly _onDidChangeCollapseState = new Emitter<ICollapseStateChangeEvent<T, TFilterData>>();
 	readonly onDidChangeCollapseState: Event<ICollapseStateChangeEvent<T, TFilterData>> = this.eventBufferer.wrapEvent(this._onDidChangeCollapseState.event);
 
-	private _onDidChangeRenderNodeCount = new Emitter<ITreeNode<T, TFilterData>>();
+	private readonly _onDidChangeRenderNodeCount = new Emitter<ITreeNode<T, TFilterData>>();
 	readonly onDidChangeRenderNodeCount: Event<ITreeNode<T, TFilterData>> = this.eventBufferer.wrapEvent(this._onDidChangeRenderNodeCount.event);
 
 	private collapseByDefault: boolean;
 	private filter?: ITreeFilter<T, TFilterData>;
 	private autoExpandSingleChildren: boolean;
 
-	private _onDidSplice = new Emitter<ITreeModelSpliceEvent<T, TFilterData>>();
+	private readonly _onDidSplice = new Emitter<ITreeModelSpliceEvent<T, TFilterData>>();
 	readonly onDidSplice = this._onDidSplice.event;
 
 	constructor(
diff --git a/src/vs/base/common/event.ts b/src/vs/base/common/event.ts
index 4d43bd8c132..d09206cd9d9 100644
--- a/src/vs/base/common/event.ts
+++ b/src/vs/base/common/event.ts
@@ -451,7 +451,7 @@ class LeakageMonitor {
  * Sample:
 	class Document {
 
-		private _onDidChange = new Emitter<(value:string)=>any>();
+		private readonly _onDidChange = new Emitter<(value:string)=>any>();
 
 		public onDidChange = this._onDidChange.event;
 
@@ -808,7 +808,7 @@ export class Relay<T> implements IDisposable {
 	private inputEvent: Event<T> = Event.None;
 	private inputEventListener: IDisposable = Disposable.None;
 
-	private emitter = new Emitter<T>({
+	private readonly emitter = new Emitter<T>({
 		onFirstListenerDidAdd: () => {
 			this.listening = true;
 			this.inputEventListener = this.inputEvent(this.emitter.fire, this.emitter);
diff --git a/src/vs/base/common/sequence.ts b/src/vs/base/common/sequence.ts
index 5d8ac1d6630..418d3907c99 100644
--- a/src/vs/base/common/sequence.ts
+++ b/src/vs/base/common/sequence.ts
@@ -24,11 +24,11 @@ export class Sequence<T> implements ISequence<T>, ISpliceable<T> {
 
 	readonly elements: T[] = [];
 
-	private _onDidSplice = new Emitter<ISplice<T>>();
+	private readonly _onDidSplice = new Emitter<ISplice<T>>();
 	readonly onDidSplice: Event<ISplice<T>> = this._onDidSplice.event;
 
 	splice(start: number, deleteCount: number, toInsert: T[] = []): void {
 		this.elements.splice(start, deleteCount, ...toInsert);
 		this._onDidSplice.fire({ start, deleteCount, toInsert });
 	}
-}
\ No newline at end of file
+}
diff --git a/src/vs/base/parts/ipc/common/ipc.net.ts b/src/vs/base/parts/ipc/common/ipc.net.ts
index 084ef5ae782..b2b939b0ba2 100644
--- a/src/vs/base/parts/ipc/common/ipc.net.ts
+++ b/src/vs/base/parts/ipc/common/ipc.net.ts
@@ -351,10 +351,10 @@ export class Protocol extends Disposable implements IMessagePassingProtocol {
 	private _socketWriter: ProtocolWriter;
 	private _socketReader: ProtocolReader;
 
-	private _onMessage = new Emitter<VSBuffer>();
+	private readonly _onMessage = new Emitter<VSBuffer>();
 	readonly onMessage: Event<VSBuffer> = this._onMessage.event;
 
-	private _onClose = new Emitter<void>();
+	private readonly _onClose = new Emitter<void>();
 	readonly onClose: Event<void> = this._onClose.event;
 
 	constructor(socket: ISocket) {
diff --git a/src/vs/base/parts/ipc/common/ipc.ts b/src/vs/base/parts/ipc/common/ipc.ts
index 392cfeaeae7..7b60ba4a101 100644
--- a/src/vs/base/parts/ipc/common/ipc.ts
+++ b/src/vs/base/parts/ipc/common/ipc.ts
@@ -442,7 +442,7 @@ export class ChannelClient implements IChannelClient, IDisposable {
 	private lastRequestId: number = 0;
 	private protocolListener: IDisposable | null;
 
-	private _onDidInitialize = new Emitter<void>();
+	private readonly _onDidInitialize = new Emitter<void>();
 	readonly onDidInitialize = this._onDidInitialize.event;
 
 	constructor(private protocol: IMessagePassingProtocol) {
@@ -660,7 +660,7 @@ export class IPCServer<TContext = string> implements IChannelServer<TContext>, I
 	private channels = new Map<string, IServerChannel<TContext>>();
 	private _connections = new Set<Connection<TContext>>();
 
-	private _onDidChangeConnections = new Emitter<Connection<TContext>>();
+	private readonly _onDidChangeConnections = new Emitter<Connection<TContext>>();
 	readonly onDidChangeConnections: Event<Connection<TContext>> = this._onDidChangeConnections.event;
 
 	get connections(): Connection<TContext>[] {
diff --git a/src/vs/base/parts/ipc/node/ipc.cp.ts b/src/vs/base/parts/ipc/node/ipc.cp.ts
index 42671a2e1a6..d930cdd4003 100644
--- a/src/vs/base/parts/ipc/node/ipc.cp.ts
+++ b/src/vs/base/parts/ipc/node/ipc.cp.ts
@@ -92,7 +92,7 @@ export class Client implements IChannelClient, IDisposable {
 	private _client: IPCClient | null;
 	private channels = new Map<string, IChannel>();
 
-	private _onDidProcessExit = new Emitter<{ code: number, signal: string }>();
+	private readonly _onDidProcessExit = new Emitter<{ code: number, signal: string }>();
 	readonly onDidProcessExit = this._onDidProcessExit.event;
 
 	constructor(private modulePath: string, private options: IIPCOptions) {
diff --git a/src/vs/base/parts/ipc/test/node/ipc.test.ts b/src/vs/base/parts/ipc/test/node/ipc.test.ts
index e30252caa76..26481f88f55 100644
--- a/src/vs/base/parts/ipc/test/node/ipc.test.ts
+++ b/src/vs/base/parts/ipc/test/node/ipc.test.ts
@@ -16,7 +16,7 @@ class QueueProtocol implements IMessagePassingProtocol {
 	private buffering = true;
 	private buffers: VSBuffer[] = [];
 
-	private _onMessage = new Emitter<VSBuffer>({
+	private readonly _onMessage = new Emitter<VSBuffer>({
 		onFirstListenerDidAdd: () => {
 			for (const buffer of this.buffers) {
 				this._onMessage.fire(buffer);
@@ -57,7 +57,7 @@ function createProtocolPair(): [IMessagePassingProtocol, IMessagePassingProtocol
 
 class TestIPCClient extends IPCClient<string> {
 
-	private _onDidDisconnect = new Emitter<void>();
+	private readonly _onDidDisconnect = new Emitter<void>();
 	readonly onDidDisconnect = this._onDidDisconnect.event;
 
 	constructor(protocol: IMessagePassingProtocol, id: string) {
@@ -107,7 +107,7 @@ interface ITestService {
 
 class TestService implements ITestService {
 
-	private _pong = new Emitter<string>();
+	private readonly _pong = new Emitter<string>();
 	readonly pong = this._pong.event;
 
 	marco(): Promise<string> {
diff --git a/src/vs/base/parts/ipc/test/node/testService.ts b/src/vs/base/parts/ipc/test/node/testService.ts
index 6784bdfc60d..505a2300a10 100644
--- a/src/vs/base/parts/ipc/test/node/testService.ts
+++ b/src/vs/base/parts/ipc/test/node/testService.ts
@@ -20,7 +20,7 @@ export interface ITestService {
 
 export class TestService implements ITestService {
 
-	private _onMarco = new Emitter<IMarcoPoloEvent>();
+	private readonly _onMarco = new Emitter<IMarcoPoloEvent>();
 	onMarco: Event<IMarcoPoloEvent> = this._onMarco.event;
 
 	marco(): Promise<string> {
@@ -76,4 +76,4 @@ export class TestServiceClient implements ITestService {
 	cancelMe(): Promise<boolean> {
 		return this.channel.call('cancelMe');
 	}
-}
\ No newline at end of file
+}
diff --git a/src/vs/base/parts/storage/test/node/storage.test.ts b/src/vs/base/parts/storage/test/node/storage.test.ts
index 4c915ef2ae7..92992e494b0 100644
--- a/src/vs/base/parts/storage/test/node/storage.test.ts
+++ b/src/vs/base/parts/storage/test/node/storage.test.ts
@@ -101,7 +101,7 @@ suite('Storage Library', () => {
 		await mkdirp(storageDir);
 
 		class TestSQLiteStorageDatabase extends SQLiteStorageDatabase {
-			private _onDidChangeItemsExternal = new Emitter<IStorageItemsChangeEvent>();
+			private readonly _onDidChangeItemsExternal = new Emitter<IStorageItemsChangeEvent>();
 			get onDidChangeItemsExternal(): Event<IStorageItemsChangeEvent> { return this._onDidChangeItemsExternal.event; }
 
 			fireDidChangeItemsExternal(event: IStorageItemsChangeEvent): void {
diff --git a/src/vs/base/parts/tree/browser/treeImpl.ts b/src/vs/base/parts/tree/browser/treeImpl.ts
index aa3e07acf8e..8b8f7b28078 100644
--- a/src/vs/base/parts/tree/browser/treeImpl.ts
+++ b/src/vs/base/parts/tree/browser/treeImpl.ts
@@ -77,7 +77,7 @@ export class Tree implements _.ITree {
 	readonly onDidExpandItem: Event<Model.IItemExpandEvent> = this._onDidExpandItem.event;
 	private _onDidCollapseItem = new Relay<Model.IItemCollapseEvent>();
 	readonly onDidCollapseItem: Event<Model.IItemCollapseEvent> = this._onDidCollapseItem.event;
-	private _onDispose = new Emitter<void>();
+	private readonly _onDispose = new Emitter<void>();
 	readonly onDidDispose: Event<void> = this._onDispose.event;
 
 	constructor(container: HTMLElement, configuration: _.ITreeConfiguration, options: _.ITreeOptions = {}) {
diff --git a/src/vs/base/parts/tree/browser/treeModel.ts b/src/vs/base/parts/tree/browser/treeModel.ts
index ba1b0d77836..30df6dc07d7 100644
--- a/src/vs/base/parts/tree/browser/treeModel.ts
+++ b/src/vs/base/parts/tree/browser/treeModel.ts
@@ -259,29 +259,29 @@ export class Item {
 
 	private traits: { [trait: string]: boolean; };
 
-	private _onDidCreate = new Emitter<Item>();
+	private readonly _onDidCreate = new Emitter<Item>();
 	readonly onDidCreate: Event<Item> = this._onDidCreate.event;
-	private _onDidReveal = new Emitter<IItemRevealEvent>();
+	private readonly _onDidReveal = new Emitter<IItemRevealEvent>();
 	readonly onDidReveal: Event<IItemRevealEvent> = this._onDidReveal.event;
-	private _onExpand = new Emitter<IItemExpandEvent>();
+	private readonly _onExpand = new Emitter<IItemExpandEvent>();
 	readonly onExpand: Event<IItemExpandEvent> = this._onExpand.event;
-	private _onDidExpand = new Emitter<IItemExpandEvent>();
+	private readonly _onDidExpand = new Emitter<IItemExpandEvent>();
 	readonly onDidExpand: Event<IItemExpandEvent> = this._onDidExpand.event;
-	private _onCollapse = new Emitter<IItemCollapseEvent>();
+	private readonly _onCollapse = new Emitter<IItemCollapseEvent>();
 	readonly onCollapse: Event<IItemCollapseEvent> = this._onCollapse.event;
-	private _onDidCollapse = new Emitter<IItemCollapseEvent>();
+	private readonly _onDidCollapse = new Emitter<IItemCollapseEvent>();
 	readonly onDidCollapse: Event<IItemCollapseEvent> = this._onDidCollapse.event;
-	private _onDidAddTrait = new Emitter<IItemTraitEvent>();
+	private readonly _onDidAddTrait = new Emitter<IItemTraitEvent>();
 	readonly onDidAddTrait: Event<IItemTraitEvent> = this._onDidAddTrait.event;
-	private _onDidRemoveTrait = new Emitter<IItemCollapseEvent>();
+	private readonly _onDidRemoveTrait = new Emitter<IItemCollapseEvent>();
 	readonly onDidRemoveTrait: Event<IItemCollapseEvent> = this._onDidRemoveTrait.event;
-	private _onDidRefresh = new Emitter<Item>();
+	private readonly _onDidRefresh = new Emitter<Item>();
 	readonly onDidRefresh: Event<Item> = this._onDidRefresh.event;
-	private _onRefreshChildren = new Emitter<IItemChildrenRefreshEvent>();
+	private readonly _onRefreshChildren = new Emitter<IItemChildrenRefreshEvent>();
 	readonly onRefreshChildren: Event<IItemChildrenRefreshEvent> = this._onRefreshChildren.event;
-	private _onDidRefreshChildren = new Emitter<IItemChildrenRefreshEvent>();
+	private readonly _onDidRefreshChildren = new Emitter<IItemChildrenRefreshEvent>();
 	readonly onDidRefreshChildren: Event<IItemChildrenRefreshEvent> = this._onDidRefreshChildren.event;
-	private _onDidDispose = new Emitter<Item>();
+	private readonly _onDidDispose = new Emitter<Item>();
 	readonly onDidDispose: Event<Item> = this._onDidDispose.event;
 
 	private _isDisposed: boolean;
@@ -868,19 +868,19 @@ export class TreeModel {
 	private registryDisposable: IDisposable = Disposable.None;
 	private traitsToItems: ITraitMap;
 
-	private _onSetInput = new Emitter<IInputEvent>();
+	private readonly _onSetInput = new Emitter<IInputEvent>();
 	readonly onSetInput: Event<IInputEvent> = this._onSetInput.event;
-	private _onDidSetInput = new Emitter<IInputEvent>();
+	private readonly _onDidSetInput = new Emitter<IInputEvent>();
 	readonly onDidSetInput: Event<IInputEvent> = this._onDidSetInput.event;
-	private _onRefresh = new Emitter<IRefreshEvent>();
+	private readonly _onRefresh = new Emitter<IRefreshEvent>();
 	readonly onRefresh: Event<IRefreshEvent> = this._onRefresh.event;
-	private _onDidRefresh = new Emitter<IRefreshEvent>();
+	private readonly _onDidRefresh = new Emitter<IRefreshEvent>();
 	readonly onDidRefresh: Event<IRefreshEvent> = this._onDidRefresh.event;
-	private _onDidHighlight = new Emitter<_.IHighlightEvent>();
+	private readonly _onDidHighlight = new Emitter<_.IHighlightEvent>();
 	readonly onDidHighlight: Event<_.IHighlightEvent> = this._onDidHighlight.event;
-	private _onDidSelect = new Emitter<_.ISelectionEvent>();
+	private readonly _onDidSelect = new Emitter<_.ISelectionEvent>();
 	readonly onDidSelect: Event<_.ISelectionEvent> = this._onDidSelect.event;
-	private _onDidFocus = new Emitter<_.IFocusEvent>();
+	private readonly _onDidFocus = new Emitter<_.IFocusEvent>();
 	readonly onDidFocus: Event<_.IFocusEvent> = this._onDidFocus.event;
 
 	private _onDidRevealItem = new Relay<IItemRevealEvent>();
diff --git a/src/vs/base/parts/tree/test/browser/treeModel.test.ts b/src/vs/base/parts/tree/test/browser/treeModel.test.ts
index 5a880d99194..18d27eefada 100644
--- a/src/vs/base/parts/tree/test/browser/treeModel.test.ts
+++ b/src/vs/base/parts/tree/test/browser/treeModel.test.ts
@@ -1081,10 +1081,10 @@ class DynamicModel implements _.IDataSource {
 	private data: any;
 	public promiseFactory: { (): Promise<any>; } | null;
 
-	private _onGetChildren = new Emitter<any>();
+	private readonly _onGetChildren = new Emitter<any>();
 	readonly onGetChildren: Event<any> = this._onGetChildren.event;
 
-	private _onDidGetChildren = new Emitter<any>();
+	private readonly _onDidGetChildren = new Emitter<any>();
 	readonly onDidGetChildren: Event<any> = this._onDidGetChildren.event;
 
 	constructor() {
diff --git a/src/vs/base/test/browser/ui/grid/util.ts b/src/vs/base/test/browser/ui/grid/util.ts
index 39a35736ddd..26b7ec06255 100644
--- a/src/vs/base/test/browser/ui/grid/util.ts
+++ b/src/vs/base/test/browser/ui/grid/util.ts
@@ -10,7 +10,7 @@ import { IView } from 'vs/base/browser/ui/grid/grid';
 
 export class TestView implements IView {
 
-	private _onDidChange = new Emitter<{ width: number; height: number; } | undefined>();
+	private readonly _onDidChange = new Emitter<{ width: number; height: number; } | undefined>();
 	readonly onDidChange = this._onDidChange.event;
 
 	get minimumWidth(): number { return this._minimumWidth; }
@@ -28,7 +28,7 @@ export class TestView implements IView {
 	private _element: HTMLElement = document.createElement('div');
 	get element(): HTMLElement { this._onDidGetElement.fire(); return this._element; }
 
-	private _onDidGetElement = new Emitter<void>();
+	private readonly _onDidGetElement = new Emitter<void>();
 	readonly onDidGetElement = this._onDidGetElement.event;
 
 	private _width = 0;
@@ -39,10 +39,10 @@ export class TestView implements IView {
 
 	get size(): [number, number] { return [this.width, this.height]; }
 
-	private _onDidLayout = new Emitter<{ width: number; height: number; }>();
+	private readonly _onDidLayout = new Emitter<{ width: number; height: number; }>();
 	readonly onDidLayout: Event<{ width: number; height: number; }> = this._onDidLayout.event;
 
-	private _onDidFocus = new Emitter<void>();
+	private readonly _onDidFocus = new Emitter<void>();
 	readonly onDidFocus: Event<void> = this._onDidFocus.event;
 
 	constructor(
diff --git a/src/vs/base/test/browser/ui/splitview/splitview.test.ts b/src/vs/base/test/browser/ui/splitview/splitview.test.ts
index c5e9cfce763..264a2bac86b 100644
--- a/src/vs/base/test/browser/ui/splitview/splitview.test.ts
+++ b/src/vs/base/test/browser/ui/splitview/splitview.test.ts
@@ -10,7 +10,7 @@ import { Sash, SashState } from 'vs/base/browser/ui/sash/sash';
 
 class TestView implements IView {
 
-	private _onDidChange = new Emitter<number | undefined>();
+	private readonly _onDidChange = new Emitter<number | undefined>();
 	readonly onDidChange = this._onDidChange.event;
 
 	get minimumSize(): number { return this._minimumSize; }
@@ -22,17 +22,17 @@ class TestView implements IView {
 	private _element: HTMLElement = document.createElement('div');
 	get element(): HTMLElement { this._onDidGetElement.fire(); return this._element; }
 
-	private _onDidGetElement = new Emitter<void>();
+	private readonly _onDidGetElement = new Emitter<void>();
 	readonly onDidGetElement = this._onDidGetElement.event;
 
 	private _size = 0;
 	get size(): number { return this._size; }
 	private _orthogonalSize: number | undefined = 0;
 	get orthogonalSize(): number | undefined { return this._orthogonalSize; }
-	private _onDidLayout = new Emitter<{ size: number; orthogonalSize: number | undefined }>();
+	private readonly _onDidLayout = new Emitter<{ size: number; orthogonalSize: number | undefined }>();
 	readonly onDidLayout = this._onDidLayout.event;
 
-	private _onDidFocus = new Emitter<void>();
+	private readonly _onDidFocus = new Emitter<void>();
 	readonly onDidFocus = this._onDidFocus.event;
 
 	constructor(
diff --git a/src/vs/base/test/common/event.test.ts b/src/vs/base/test/common/event.test.ts
index 039743bbb39..09f3f6eec81 100644
--- a/src/vs/base/test/common/event.test.ts
+++ b/src/vs/base/test/common/event.test.ts
@@ -25,7 +25,7 @@ namespace Samples {
 
 	export class Document3 {
 
-		private _onDidChange = new Emitter<string>();
+		private readonly _onDidChange = new Emitter<string>();
 
 		onDidChange: Event<string> = this._onDidChange.event;
 
diff --git a/src/vs/editor/common/view/minimapCharRenderer.ts b/src/vs/editor/common/view/minimapCharRenderer.ts
index 17c835d8c2e..f47962e4c0f 100644
--- a/src/vs/editor/common/view/minimapCharRenderer.ts
+++ b/src/vs/editor/common/view/minimapCharRenderer.ts
@@ -19,7 +19,7 @@ export class MinimapTokensColorTracker {
 	private _colors!: RGBA8[];
 	private _backgroundIsLight!: boolean;
 
-	private _onDidChange = new Emitter<void>();
+	private readonly _onDidChange = new Emitter<void>();
 	public readonly onDidChange: Event<void> = this._onDidChange.event;
 
 	private constructor() {
diff --git a/src/vs/editor/contrib/colorPicker/colorPickerModel.ts b/src/vs/editor/contrib/colorPicker/colorPickerModel.ts
index cfeda974e3c..9b974876732 100644
--- a/src/vs/editor/contrib/colorPicker/colorPickerModel.ts
+++ b/src/vs/editor/contrib/colorPicker/colorPickerModel.ts
@@ -41,13 +41,13 @@ export class ColorPickerModel {
 		this._onDidChangePresentation.fire(this.presentation);
 	}
 
-	private _onColorFlushed = new Emitter<Color>();
+	private readonly _onColorFlushed = new Emitter<Color>();
 	readonly onColorFlushed: Event<Color> = this._onColorFlushed.event;
 
-	private _onDidChangeColor = new Emitter<Color>();
+	private readonly _onDidChangeColor = new Emitter<Color>();
 	readonly onDidChangeColor: Event<Color> = this._onDidChangeColor.event;
 
-	private _onDidChangePresentation = new Emitter<IColorPresentation>();
+	private readonly _onDidChangePresentation = new Emitter<IColorPresentation>();
 	readonly onDidChangePresentation: Event<IColorPresentation> = this._onDidChangePresentation.event;
 
 	constructor(color: Color, availableColorPresentations: IColorPresentation[], private presentationIndex: number) {
diff --git a/src/vs/editor/contrib/colorPicker/colorPickerWidget.ts b/src/vs/editor/contrib/colorPicker/colorPickerWidget.ts
index b4e8404b423..64329a79ba9 100644
--- a/src/vs/editor/contrib/colorPicker/colorPickerWidget.ts
+++ b/src/vs/editor/contrib/colorPicker/colorPickerWidget.ts
@@ -127,10 +127,10 @@ class SaturationBox extends Disposable {
 	private height!: number;
 
 	private monitor: GlobalMouseMoveMonitor<IStandardMouseMoveEventData> | null;
-	private _onDidChange = new Emitter<{ s: number, v: number }>();
+	private readonly _onDidChange = new Emitter<{ s: number, v: number }>();
 	readonly onDidChange: Event<{ s: number, v: number }> = this._onDidChange.event;
 
-	private _onColorFlushed = new Emitter<void>();
+	private readonly _onColorFlushed = new Emitter<void>();
 	readonly onColorFlushed: Event<void> = this._onColorFlushed.event;
 
 	constructor(container: HTMLElement, private readonly model: ColorPickerModel, private pixelRatio: number) {
@@ -237,10 +237,10 @@ abstract class Strip extends Disposable {
 	protected slider: HTMLElement;
 	private height!: number;
 
-	private _onDidChange = new Emitter<number>();
+	private readonly _onDidChange = new Emitter<number>();
 	readonly onDidChange: Event<number> = this._onDidChange.event;
 
-	private _onColorFlushed = new Emitter<void>();
+	private readonly _onColorFlushed = new Emitter<void>();
 	readonly onColorFlushed: Event<void> = this._onColorFlushed.event;
 
 	constructor(container: HTMLElement, protected model: ColorPickerModel) {
diff --git a/src/vs/editor/contrib/folding/foldingModel.ts b/src/vs/editor/contrib/folding/foldingModel.ts
index e81b529d061..15cc62d2098 100644
--- a/src/vs/editor/contrib/folding/foldingModel.ts
+++ b/src/vs/editor/contrib/folding/foldingModel.ts
@@ -28,7 +28,7 @@ export class FoldingModel {
 	private _editorDecorationIds: string[];
 	private _isInitialized: boolean;
 
-	private _updateEventEmitter = new Emitter<FoldingModelChangeEvent>();
+	private readonly _updateEventEmitter = new Emitter<FoldingModelChangeEvent>();
 	public readonly onDidChange: Event<FoldingModelChangeEvent> = this._updateEventEmitter.event;
 
 	public get regions(): FoldingRegions { return this._regions; }
diff --git a/src/vs/editor/contrib/folding/hiddenRangeModel.ts b/src/vs/editor/contrib/folding/hiddenRangeModel.ts
index 96205183819..0e0f0b390f0 100644
--- a/src/vs/editor/contrib/folding/hiddenRangeModel.ts
+++ b/src/vs/editor/contrib/folding/hiddenRangeModel.ts
@@ -14,7 +14,7 @@ export class HiddenRangeModel {
 	private readonly _foldingModel: FoldingModel;
 	private _hiddenRanges: IRange[];
 	private _foldingModelListener: IDisposable | null;
-	private _updateEventEmitter = new Emitter<IRange[]>();
+	private readonly _updateEventEmitter = new Emitter<IRange[]>();
 
 	public get onDidChange(): Event<IRange[]> { return this._updateEventEmitter.event; }
 	public get hiddenRanges() { return this._hiddenRanges; }
@@ -154,4 +154,4 @@ function findRange(ranges: IRange[], line: number): IRange | null {
 		return ranges[i];
 	}
 	return null;
-}
\ No newline at end of file
+}
diff --git a/src/vs/editor/contrib/gotoError/gotoErrorWidget.ts b/src/vs/editor/contrib/gotoError/gotoErrorWidget.ts
index 705728c05f4..3c94a3b561a 100644
--- a/src/vs/editor/contrib/gotoError/gotoErrorWidget.ts
+++ b/src/vs/editor/contrib/gotoError/gotoErrorWidget.ts
@@ -173,7 +173,7 @@ export class MarkerNavigationWidget extends PeekViewWidget {
 	private readonly _callOnDispose = new DisposableStore();
 	private _severity: MarkerSeverity;
 	private _backgroundColor?: Color;
-	private _onDidSelectRelatedInformation = new Emitter<IRelatedInformation>();
+	private readonly _onDidSelectRelatedInformation = new Emitter<IRelatedInformation>();
 	private _heightInPixel!: number;
 
 	readonly onDidSelectRelatedInformation: Event<IRelatedInformation> = this._onDidSelectRelatedInformation.event;
diff --git a/src/vs/editor/contrib/referenceSearch/peekViewWidget.ts b/src/vs/editor/contrib/referenceSearch/peekViewWidget.ts
index 8db8f79203b..2d2d5113f7b 100644
--- a/src/vs/editor/contrib/referenceSearch/peekViewWidget.ts
+++ b/src/vs/editor/contrib/referenceSearch/peekViewWidget.ts
@@ -83,7 +83,7 @@ export abstract class PeekViewWidget extends ZoneWidget {
 
 	public _serviceBrand: undefined;
 
-	private _onDidClose = new Emitter<PeekViewWidget>();
+	private readonly _onDidClose = new Emitter<PeekViewWidget>();
 
 	protected _headElement?: HTMLDivElement;
 	protected _primaryHeading?: HTMLElement;
diff --git a/src/vs/editor/contrib/referenceSearch/referencesWidget.ts b/src/vs/editor/contrib/referenceSearch/referencesWidget.ts
index 26eca18fb11..627902b09b9 100644
--- a/src/vs/editor/contrib/referenceSearch/referencesWidget.ts
+++ b/src/vs/editor/contrib/referenceSearch/referencesWidget.ts
@@ -196,7 +196,7 @@ export class ReferenceWidget extends PeekViewWidget {
 
 	private readonly _disposeOnNewModel = new DisposableStore();
 	private readonly _callOnDispose = new DisposableStore();
-	private _onDidSelectReference = new Emitter<SelectionEvent>();
+	private readonly _onDidSelectReference = new Emitter<SelectionEvent>();
 
 	private _tree!: WorkbenchAsyncDataTree<ReferencesModel | FileReferences, TreeElement, FuzzyScore>;
 	private _treeContainer!: HTMLElement;
diff --git a/src/vs/editor/contrib/suggest/suggestWidget.ts b/src/vs/editor/contrib/suggest/suggestWidget.ts
index fa7198d184c..70e4d14e5ba 100644
--- a/src/vs/editor/contrib/suggest/suggestWidget.ts
+++ b/src/vs/editor/contrib/suggest/suggestWidget.ts
@@ -450,10 +450,10 @@ export class SuggestWidget implements IContentWidget, IListVirtualDelegate<Compl
 	private readonly showTimeout = new TimeoutTimer();
 	private readonly toDispose = new DisposableStore();
 
-	private onDidSelectEmitter = new Emitter<ISelectedSuggestion>();
-	private onDidFocusEmitter = new Emitter<ISelectedSuggestion>();
-	private onDidHideEmitter = new Emitter<this>();
-	private onDidShowEmitter = new Emitter<this>();
+	private readonly onDidSelectEmitter = new Emitter<ISelectedSuggestion>();
+	private readonly onDidFocusEmitter = new Emitter<ISelectedSuggestion>();
+	private readonly onDidHideEmitter = new Emitter<this>();
+	private readonly onDidShowEmitter = new Emitter<this>();
 
 	readonly onDidSelect: Event<ISelectedSuggestion> = this.onDidSelectEmitter.event;
 	readonly onDidFocus: Event<ISelectedSuggestion> = this.onDidFocusEmitter.event;
diff --git a/src/vs/editor/standalone/browser/simpleServices.ts b/src/vs/editor/standalone/browser/simpleServices.ts
index d0da84973a7..372ceb0deab 100644
--- a/src/vs/editor/standalone/browser/simpleServices.ts
+++ b/src/vs/editor/standalone/browser/simpleServices.ts
@@ -420,7 +420,7 @@ export class SimpleConfigurationService implements IConfigurationService {
 
 	_serviceBrand: undefined;
 
-	private _onDidChangeConfiguration = new Emitter<IConfigurationChangeEvent>();
+	private readonly _onDidChangeConfiguration = new Emitter<IConfigurationChangeEvent>();
 	public readonly onDidChangeConfiguration: Event<IConfigurationChangeEvent> = this._onDidChangeConfiguration.event;
 
 	private readonly _configuration: Configuration;
diff --git a/src/vs/platform/debug/common/extensionHostDebugIpc.ts b/src/vs/platform/debug/common/extensionHostDebugIpc.ts
index 555d90bfde0..e342490136d 100644
--- a/src/vs/platform/debug/common/extensionHostDebugIpc.ts
+++ b/src/vs/platform/debug/common/extensionHostDebugIpc.ts
@@ -15,11 +15,11 @@ export class ExtensionHostDebugBroadcastChannel<TContext> implements IServerChan
 
 	static readonly ChannelName = 'extensionhostdebugservice';
 
-	private _onCloseEmitter = new Emitter<ICloseSessionEvent>();
-	private _onReloadEmitter = new Emitter<IReloadSessionEvent>();
-	private _onTerminateEmitter = new Emitter<ITerminateSessionEvent>();
-	private _onLogToEmitter = new Emitter<ILogToSessionEvent>();
-	private _onAttachEmitter = new Emitter<IAttachSessionEvent>();
+	private readonly _onCloseEmitter = new Emitter<ICloseSessionEvent>();
+	private readonly _onReloadEmitter = new Emitter<IReloadSessionEvent>();
+	private readonly _onTerminateEmitter = new Emitter<ITerminateSessionEvent>();
+	private readonly _onLogToEmitter = new Emitter<ILogToSessionEvent>();
+	private readonly _onAttachEmitter = new Emitter<IAttachSessionEvent>();
 
 	call(ctx: TContext, command: string, arg?: any): Promise<any> {
 		switch (command) {
diff --git a/src/vs/platform/driver/electron-main/driver.ts b/src/vs/platform/driver/electron-main/driver.ts
index 9101eeb28ce..a0e9f373504 100644
--- a/src/vs/platform/driver/electron-main/driver.ts
+++ b/src/vs/platform/driver/electron-main/driver.ts
@@ -30,7 +30,7 @@ export class Driver implements IDriver, IWindowDriverRegistry {
 
 	private registeredWindowIds = new Set<number>();
 	private reloadingWindowIds = new Set<number>();
-	private onDidReloadingChange = new Emitter<void>();
+	private readonly onDidReloadingChange = new Emitter<void>();
 
 	constructor(
 		private windowServer: IPCServer,
diff --git a/src/vs/platform/files/node/watcher/nsfw/nsfwWatcherService.ts b/src/vs/platform/files/node/watcher/nsfw/nsfwWatcherService.ts
index 916a0492077..582d0bc8754 100644
--- a/src/vs/platform/files/node/watcher/nsfw/nsfwWatcherService.ts
+++ b/src/vs/platform/files/node/watcher/nsfw/nsfwWatcherService.ts
@@ -39,10 +39,10 @@ export class NsfwWatcherService implements IWatcherService {
 	private _verboseLogging: boolean | undefined;
 	private enospcErrorLogged: boolean | undefined;
 
-	private _onWatchEvent = new Emitter<IDiskFileChange[]>();
+	private readonly _onWatchEvent = new Emitter<IDiskFileChange[]>();
 	readonly onWatchEvent = this._onWatchEvent.event;
 
-	private _onLogMessage = new Emitter<ILogMessage>();
+	private readonly _onLogMessage = new Emitter<ILogMessage>();
 	readonly onLogMessage: Event<ILogMessage> = this._onLogMessage.event;
 
 	watch(options: IWatcherOptions): Event<IDiskFileChange[]> {
diff --git a/src/vs/platform/files/node/watcher/unix/chokidarWatcherService.ts b/src/vs/platform/files/node/watcher/unix/chokidarWatcherService.ts
index 2600512e0e7..f12dfef68bc 100644
--- a/src/vs/platform/files/node/watcher/unix/chokidarWatcherService.ts
+++ b/src/vs/platform/files/node/watcher/unix/chokidarWatcherService.ts
@@ -43,10 +43,10 @@ export class ChokidarWatcherService implements IWatcherService {
 	private spamWarningLogged: boolean | undefined;
 	private enospcErrorLogged: boolean | undefined;
 
-	private _onWatchEvent = new Emitter<IDiskFileChange[]>();
+	private readonly _onWatchEvent = new Emitter<IDiskFileChange[]>();
 	readonly onWatchEvent = this._onWatchEvent.event;
 
-	private _onLogMessage = new Emitter<ILogMessage>();
+	private readonly _onLogMessage = new Emitter<ILogMessage>();
 	readonly onLogMessage: Event<ILogMessage> = this._onLogMessage.event;
 
 	public watch(options: IWatcherOptions): Event<IDiskFileChange[]> {
diff --git a/src/vs/platform/history/electron-main/historyMainService.ts b/src/vs/platform/history/electron-main/historyMainService.ts
index 95055636e3c..54ca0d95c81 100644
--- a/src/vs/platform/history/electron-main/historyMainService.ts
+++ b/src/vs/platform/history/electron-main/historyMainService.ts
@@ -59,7 +59,7 @@ export class HistoryMainService implements IHistoryMainService {
 
 	_serviceBrand: undefined;
 
-	private _onRecentlyOpenedChange = new Emitter<void>();
+	private readonly _onRecentlyOpenedChange = new Emitter<void>();
 	readonly onRecentlyOpenedChange: CommonEvent<void> = this._onRecentlyOpenedChange.event;
 
 	private macOSRecentDocumentsUpdater: ThrottledDelayer<void>;
diff --git a/src/vs/platform/markers/common/markerService.ts b/src/vs/platform/markers/common/markerService.ts
index 3959296f926..9bd5e64f123 100644
--- a/src/vs/platform/markers/common/markerService.ts
+++ b/src/vs/platform/markers/common/markerService.ts
@@ -123,7 +123,7 @@ export class MarkerService implements IMarkerService {
 
 	_serviceBrand: undefined;
 
-	private _onMarkerChanged = new Emitter<URI[]>();
+	private readonly _onMarkerChanged = new Emitter<URI[]>();
 	private _onMarkerChangedEvent: Event<URI[]> = Event.debounce(this._onMarkerChanged.event, MarkerService._debouncer, 0);
 	private _byResource: MapMap<IMarker[]> = Object.create(null);
 	private _byOwner: MapMap<IMarker[]> = Object.create(null);
diff --git a/src/vs/platform/update/electron-browser/updateService.ts b/src/vs/platform/update/electron-browser/updateService.ts
index fe6e5be934a..95632dead57 100644
--- a/src/vs/platform/update/electron-browser/updateService.ts
+++ b/src/vs/platform/update/electron-browser/updateService.ts
@@ -12,7 +12,7 @@ export class UpdateService implements IUpdateService {
 
 	_serviceBrand: undefined;
 
-	private _onStateChange = new Emitter<State>();
+	private readonly _onStateChange = new Emitter<State>();
 	readonly onStateChange: Event<State> = this._onStateChange.event;
 
 	private _state: State = State.Uninitialized;
diff --git a/src/vs/platform/update/electron-main/abstractUpdateService.ts b/src/vs/platform/update/electron-main/abstractUpdateService.ts
index 276c468a51a..8a1c95d37be 100644
--- a/src/vs/platform/update/electron-main/abstractUpdateService.ts
+++ b/src/vs/platform/update/electron-main/abstractUpdateService.ts
@@ -30,7 +30,7 @@ export abstract class AbstractUpdateService implements IUpdateService {
 
 	private _state: State = State.Uninitialized;
 
-	private _onStateChange = new Emitter<State>();
+	private readonly _onStateChange = new Emitter<State>();
 	readonly onStateChange: Event<State> = this._onStateChange.event;
 
 	get state(): State {
diff --git a/src/vs/platform/update/electron-main/updateService.snap.ts b/src/vs/platform/update/electron-main/updateService.snap.ts
index 75d7c1e187e..3516b44ad2c 100644
--- a/src/vs/platform/update/electron-main/updateService.snap.ts
+++ b/src/vs/platform/update/electron-main/updateService.snap.ts
@@ -21,7 +21,7 @@ abstract class AbstractUpdateService2 implements IUpdateService {
 
 	private _state: State = State.Uninitialized;
 
-	private _onStateChange = new Emitter<State>();
+	private readonly _onStateChange = new Emitter<State>();
 	readonly onStateChange: Event<State> = this._onStateChange.event;
 
 	get state(): State {
diff --git a/src/vs/workbench/api/browser/mainThreadComments.ts b/src/vs/workbench/api/browser/mainThreadComments.ts
index bbd29b585a2..658199aebaa 100644
--- a/src/vs/workbench/api/browser/mainThreadComments.ts
+++ b/src/vs/workbench/api/browser/mainThreadComments.ts
@@ -33,7 +33,7 @@ export class MainThreadCommentThread implements modes.CommentThread {
 		this._onDidChangeInput.fire(value);
 	}
 
-	private _onDidChangeInput = new Emitter<modes.CommentInput | undefined>();
+	private readonly _onDidChangeInput = new Emitter<modes.CommentInput | undefined>();
 	get onDidChangeInput(): Event<modes.CommentInput | undefined> { return this._onDidChangeInput.event; }
 
 	private _label: string | undefined;
@@ -57,7 +57,7 @@ export class MainThreadCommentThread implements modes.CommentThread {
 		this._contextValue = context;
 	}
 
-	private _onDidChangeLabel = new Emitter<string | undefined>();
+	private readonly _onDidChangeLabel = new Emitter<string | undefined>();
 	readonly onDidChangeLabel: Event<string | undefined> = this._onDidChangeLabel.event;
 
 	private _comments: modes.Comment[] | undefined;
@@ -71,7 +71,7 @@ export class MainThreadCommentThread implements modes.CommentThread {
 		this._onDidChangeComments.fire(this._comments);
 	}
 
-	private _onDidChangeComments = new Emitter<modes.Comment[] | undefined>();
+	private readonly _onDidChangeComments = new Emitter<modes.Comment[] | undefined>();
 	get onDidChangeComments(): Event<modes.Comment[] | undefined> { return this._onDidChangeComments.event; }
 
 	set range(range: IRange) {
@@ -83,7 +83,7 @@ export class MainThreadCommentThread implements modes.CommentThread {
 		return this._range;
 	}
 
-	private _onDidChangeRange = new Emitter<IRange>();
+	private readonly _onDidChangeRange = new Emitter<IRange>();
 	public onDidChangeRange = this._onDidChangeRange.event;
 
 	private _collapsibleState: modes.CommentThreadCollapsibleState | undefined;
@@ -96,7 +96,7 @@ export class MainThreadCommentThread implements modes.CommentThread {
 		this._onDidChangeCollasibleState.fire(this._collapsibleState);
 	}
 
-	private _onDidChangeCollasibleState = new Emitter<modes.CommentThreadCollapsibleState | undefined>();
+	private readonly _onDidChangeCollasibleState = new Emitter<modes.CommentThreadCollapsibleState | undefined>();
 	public onDidChangeCollasibleState = this._onDidChangeCollasibleState.event;
 
 	private _isDisposed: boolean;
diff --git a/src/vs/workbench/api/browser/mainThreadDocumentsAndEditors.ts b/src/vs/workbench/api/browser/mainThreadDocumentsAndEditors.ts
index 10037f6c21a..fdd407e642a 100644
--- a/src/vs/workbench/api/browser/mainThreadDocumentsAndEditors.ts
+++ b/src/vs/workbench/api/browser/mainThreadDocumentsAndEditors.ts
@@ -308,10 +308,10 @@ export class MainThreadDocumentsAndEditors {
 	private readonly _proxy: ExtHostDocumentsAndEditorsShape;
 	private readonly _textEditors = new Map<string, MainThreadTextEditor>();
 
-	private _onTextEditorAdd = new Emitter<MainThreadTextEditor[]>();
-	private _onTextEditorRemove = new Emitter<string[]>();
-	private _onDocumentAdd = new Emitter<ITextModel[]>();
-	private _onDocumentRemove = new Emitter<URI[]>();
+	private readonly _onTextEditorAdd = new Emitter<MainThreadTextEditor[]>();
+	private readonly _onTextEditorRemove = new Emitter<string[]>();
+	private readonly _onDocumentAdd = new Emitter<ITextModel[]>();
+	private readonly _onDocumentRemove = new Emitter<URI[]>();
 
 	readonly onTextEditorAdd: Event<MainThreadTextEditor[]> = this._onTextEditorAdd.event;
 	readonly onTextEditorRemove: Event<string[]> = this._onTextEditorRemove.event;
diff --git a/src/vs/workbench/api/browser/mainThreadSCM.ts b/src/vs/workbench/api/browser/mainThreadSCM.ts
index e71a7c8a007..4488720cf9a 100644
--- a/src/vs/workbench/api/browser/mainThreadSCM.ts
+++ b/src/vs/workbench/api/browser/mainThreadSCM.ts
@@ -18,12 +18,12 @@ class MainThreadSCMResourceGroup implements ISCMResourceGroup {
 
 	readonly elements: ISCMResource[] = [];
 
-	private _onDidSplice = new Emitter<ISplice<ISCMResource>>();
+	private readonly _onDidSplice = new Emitter<ISplice<ISCMResource>>();
 	readonly onDidSplice = this._onDidSplice.event;
 
 	get hideWhenEmpty(): boolean { return !!this.features.hideWhenEmpty; }
 
-	private _onDidChange = new Emitter<void>();
+	private readonly _onDidChange = new Emitter<void>();
 	readonly onDidChange: Event<void> = this._onDidChange.event;
 
 	constructor(
@@ -104,7 +104,7 @@ class MainThreadSCMProvider implements ISCMProvider {
 	// 	// 	.filter(g => g.resources.elements.length > 0 || !g.features.hideWhenEmpty);
 	// }
 
-	private _onDidChangeResources = new Emitter<void>();
+	private readonly _onDidChangeResources = new Emitter<void>();
 	readonly onDidChangeResources: Event<void> = this._onDidChangeResources.event;
 
 	private features: SCMProviderFeatures = {};
@@ -119,13 +119,13 @@ class MainThreadSCMProvider implements ISCMProvider {
 	get statusBarCommands(): Command[] | undefined { return this.features.statusBarCommands; }
 	get count(): number | undefined { return this.features.count; }
 
-	private _onDidChangeCommitTemplate = new Emitter<string>();
+	private readonly _onDidChangeCommitTemplate = new Emitter<string>();
 	readonly onDidChangeCommitTemplate: Event<string> = this._onDidChangeCommitTemplate.event;
 
-	private _onDidChangeStatusBarCommands = new Emitter<Command[]>();
+	private readonly _onDidChangeStatusBarCommands = new Emitter<Command[]>();
 	get onDidChangeStatusBarCommands(): Event<Command[]> { return this._onDidChangeStatusBarCommands.event; }
 
-	private _onDidChange = new Emitter<void>();
+	private readonly _onDidChange = new Emitter<void>();
 	readonly onDidChange: Event<void> = this._onDidChange.event;
 
 	constructor(
diff --git a/src/vs/workbench/api/common/extHostComments.ts b/src/vs/workbench/api/common/extHostComments.ts
index b4057f98164..5fac49d7eda 100644
--- a/src/vs/workbench/api/common/extHostComments.ts
+++ b/src/vs/workbench/api/common/extHostComments.ts
@@ -239,7 +239,7 @@ export class ExtHostCommentThread implements vscode.CommentThread {
 		return this._uri;
 	}
 
-	private _onDidUpdateCommentThread = new Emitter<void>();
+	private readonly _onDidUpdateCommentThread = new Emitter<void>();
 	readonly onDidUpdateCommentThread = this._onDidUpdateCommentThread.event;
 
 	set range(range: vscode.Range) {
diff --git a/src/vs/workbench/api/common/extHostDocuments.ts b/src/vs/workbench/api/common/extHostDocuments.ts
index fc8bc68cb40..ea9e189ce51 100644
--- a/src/vs/workbench/api/common/extHostDocuments.ts
+++ b/src/vs/workbench/api/common/extHostDocuments.ts
@@ -15,10 +15,10 @@ import * as vscode from 'vscode';
 
 export class ExtHostDocuments implements ExtHostDocumentsShape {
 
-	private _onDidAddDocument = new Emitter<vscode.TextDocument>();
-	private _onDidRemoveDocument = new Emitter<vscode.TextDocument>();
-	private _onDidChangeDocument = new Emitter<vscode.TextDocumentChangeEvent>();
-	private _onDidSaveDocument = new Emitter<vscode.TextDocument>();
+	private readonly _onDidAddDocument = new Emitter<vscode.TextDocument>();
+	private readonly _onDidRemoveDocument = new Emitter<vscode.TextDocument>();
+	private readonly _onDidChangeDocument = new Emitter<vscode.TextDocumentChangeEvent>();
+	private readonly _onDidSaveDocument = new Emitter<vscode.TextDocument>();
 
 	readonly onDidAddDocument: Event<vscode.TextDocument> = this._onDidAddDocument.event;
 	readonly onDidRemoveDocument: Event<vscode.TextDocument> = this._onDidRemoveDocument.event;
diff --git a/src/vs/workbench/api/common/extHostFileSystemEventService.ts b/src/vs/workbench/api/common/extHostFileSystemEventService.ts
index 5ed5945f2f5..8658c24bb14 100644
--- a/src/vs/workbench/api/common/extHostFileSystemEventService.ts
+++ b/src/vs/workbench/api/common/extHostFileSystemEventService.ts
@@ -16,9 +16,9 @@ import { IExtensionDescription } from 'vs/platform/extensions/common/extensions'
 
 class FileSystemWatcher implements vscode.FileSystemWatcher {
 
-	private _onDidCreate = new Emitter<vscode.Uri>();
-	private _onDidChange = new Emitter<vscode.Uri>();
-	private _onDidDelete = new Emitter<vscode.Uri>();
+	private readonly _onDidCreate = new Emitter<vscode.Uri>();
+	private readonly _onDidChange = new Emitter<vscode.Uri>();
+	private readonly _onDidDelete = new Emitter<vscode.Uri>();
 	private _disposable: Disposable;
 	private _config: number;
 
diff --git a/src/vs/workbench/api/common/extHostQuickOpen.ts b/src/vs/workbench/api/common/extHostQuickOpen.ts
index 467b05f5c96..3d790f26276 100644
--- a/src/vs/workbench/api/common/extHostQuickOpen.ts
+++ b/src/vs/workbench/api/common/extHostQuickOpen.ts
@@ -246,10 +246,10 @@ class ExtHostQuickInput implements QuickInput {
 	private _placeholder: string;
 	private _buttons: QuickInputButton[] = [];
 	private _handlesToButtons = new Map<number, QuickInputButton>();
-	private _onDidAcceptEmitter = new Emitter<void>();
-	private _onDidChangeValueEmitter = new Emitter<string>();
-	private _onDidTriggerButtonEmitter = new Emitter<QuickInputButton>();
-	private _onDidHideEmitter = new Emitter<void>();
+	private readonly _onDidAcceptEmitter = new Emitter<void>();
+	private readonly _onDidChangeValueEmitter = new Emitter<string>();
+	private readonly _onDidTriggerButtonEmitter = new Emitter<QuickInputButton>();
+	private readonly _onDidHideEmitter = new Emitter<void>();
 	private _updateTimeout: any;
 	private _pendingUpdate: TransferQuickInput = { id: this._id };
 
@@ -486,9 +486,9 @@ class ExtHostQuickPick<T extends QuickPickItem> extends ExtHostQuickInput implem
 	private _matchOnDescription = true;
 	private _matchOnDetail = true;
 	private _activeItems: T[] = [];
-	private _onDidChangeActiveEmitter = new Emitter<T[]>();
+	private readonly _onDidChangeActiveEmitter = new Emitter<T[]>();
 	private _selectedItems: T[] = [];
-	private _onDidChangeSelectionEmitter = new Emitter<T[]>();
+	private readonly _onDidChangeSelectionEmitter = new Emitter<T[]>();
 
 	constructor(proxy: MainThreadQuickOpenShape, extensionId: ExtensionIdentifier, enableProposedApi: boolean, onDispose: () => void) {
 		super(proxy, extensionId, onDispose);
diff --git a/src/vs/workbench/api/common/extHostSCM.ts b/src/vs/workbench/api/common/extHostSCM.ts
index 9ab1b497761..80c0c007f65 100644
--- a/src/vs/workbench/api/common/extHostSCM.ts
+++ b/src/vs/workbench/api/common/extHostSCM.ts
@@ -157,7 +157,7 @@ export class ExtHostSCMInputBox implements vscode.SourceControlInputBox {
 		this.updateValue(value);
 	}
 
-	private _onDidChange = new Emitter<string>();
+	private readonly _onDidChange = new Emitter<string>();
 
 	get onDidChange(): Event<string> {
 		return this._onDidChange.event;
@@ -233,9 +233,9 @@ class ExtHostSourceControlResourceGroup implements vscode.SourceControlResourceG
 	private _resourceStatesMap: Map<ResourceStateHandle, vscode.SourceControlResourceState> = new Map<ResourceStateHandle, vscode.SourceControlResourceState>();
 	private _resourceStatesCommandsMap: Map<ResourceStateHandle, vscode.Command> = new Map<ResourceStateHandle, vscode.Command>();
 
-	private _onDidUpdateResourceStates = new Emitter<void>();
+	private readonly _onDidUpdateResourceStates = new Emitter<void>();
 	readonly onDidUpdateResourceStates = this._onDidUpdateResourceStates.event;
-	private _onDidDispose = new Emitter<void>();
+	private readonly _onDidDispose = new Emitter<void>();
 	readonly onDidDispose = this._onDidDispose.event;
 
 	private _handlesSnapshot: number[] = [];
@@ -451,7 +451,7 @@ class ExtHostSourceControl implements vscode.SourceControl {
 		return this._selected;
 	}
 
-	private _onDidChangeSelection = new Emitter<boolean>();
+	private readonly _onDidChangeSelection = new Emitter<boolean>();
 	readonly onDidChangeSelection = this._onDidChangeSelection.event;
 
 	private handle: number = ExtHostSourceControl._handlePool++;
@@ -535,7 +535,7 @@ export class ExtHostSCM implements ExtHostSCMShape {
 	private _sourceControls: Map<ProviderHandle, ExtHostSourceControl> = new Map<ProviderHandle, ExtHostSourceControl>();
 	private _sourceControlsByExtension: Map<string, ExtHostSourceControl[]> = new Map<string, ExtHostSourceControl[]>();
 
-	private _onDidChangeActiveProvider = new Emitter<vscode.SourceControl>();
+	private readonly _onDidChangeActiveProvider = new Emitter<vscode.SourceControl>();
 	get onDidChangeActiveProvider(): Event<vscode.SourceControl> { return this._onDidChangeActiveProvider.event; }
 
 	private _selectedSourceControlHandles = new Set<number>();
diff --git a/src/vs/workbench/api/common/extHostStorage.ts b/src/vs/workbench/api/common/extHostStorage.ts
index 71bb81ef6c8..8c87a3ea33c 100644
--- a/src/vs/workbench/api/common/extHostStorage.ts
+++ b/src/vs/workbench/api/common/extHostStorage.ts
@@ -20,7 +20,7 @@ export class ExtHostStorage implements ExtHostStorageShape {
 
 	private _proxy: MainThreadStorageShape;
 
-	private _onDidChangeStorage = new Emitter<IStorageChangeEvent>();
+	private readonly _onDidChangeStorage = new Emitter<IStorageChangeEvent>();
 	readonly onDidChangeStorage = this._onDidChangeStorage.event;
 
 	constructor(mainContext: IExtHostRpcService) {
diff --git a/src/vs/workbench/api/common/extHostWindow.ts b/src/vs/workbench/api/common/extHostWindow.ts
index fa36961f152..7017c29788e 100644
--- a/src/vs/workbench/api/common/extHostWindow.ts
+++ b/src/vs/workbench/api/common/extHostWindow.ts
@@ -18,7 +18,7 @@ export class ExtHostWindow implements ExtHostWindowShape {
 
 	private _proxy: MainThreadWindowShape;
 
-	private _onDidChangeWindowState = new Emitter<WindowState>();
+	private readonly _onDidChangeWindowState = new Emitter<WindowState>();
 	readonly onDidChangeWindowState: Event<WindowState> = this._onDidChangeWindowState.event;
 
 	private _state = ExtHostWindow.InitialState;
diff --git a/src/vs/workbench/browser/parts/compositeBarActions.ts b/src/vs/workbench/browser/parts/compositeBarActions.ts
index d93d9aec8b7..33c609eba58 100644
--- a/src/vs/workbench/browser/parts/compositeBarActions.ts
+++ b/src/vs/workbench/browser/parts/compositeBarActions.ts
@@ -51,10 +51,10 @@ export interface ICompositeBar {
 
 export class ActivityAction extends Action {
 
-	private _onDidChangeActivity = new Emitter<this>();
+	private readonly _onDidChangeActivity = new Emitter<this>();
 	readonly onDidChangeActivity: Event<this> = this._onDidChangeActivity.event;
 
-	private _onDidChangeBadge = new Emitter<this>();
+	private readonly _onDidChangeBadge = new Emitter<this>();
 	readonly onDidChangeBadge: Event<this> = this._onDidChangeBadge.event;
 
 	private badge?: IBadge;
diff --git a/src/vs/workbench/browser/parts/editor/breadcrumbsModel.ts b/src/vs/workbench/browser/parts/editor/breadcrumbsModel.ts
index 73b3e5f7664..c6f7164cc8e 100644
--- a/src/vs/workbench/browser/parts/editor/breadcrumbsModel.ts
+++ b/src/vs/workbench/browser/parts/editor/breadcrumbsModel.ts
@@ -45,7 +45,7 @@ export class EditorBreadcrumbsModel {
 	private _outlineElements: Array<OutlineModel | OutlineGroup | OutlineElement> = [];
 	private _outlineDisposables = new DisposableStore();
 
-	private _onDidUpdate = new Emitter<this>();
+	private readonly _onDidUpdate = new Emitter<this>();
 	readonly onDidUpdate: Event<this> = this._onDidUpdate.event;
 
 	constructor(
diff --git a/src/vs/workbench/browser/parts/quickinput/quickInputList.ts b/src/vs/workbench/browser/parts/quickinput/quickInputList.ts
index c5b9c04fb5d..4c992ffd94f 100644
--- a/src/vs/workbench/browser/parts/quickinput/quickInputList.ts
+++ b/src/vs/workbench/browser/parts/quickinput/quickInputList.ts
@@ -50,7 +50,7 @@ class ListElement implements IListElement {
 	saneDescription?: string;
 	saneDetail?: string;
 	hidden = false;
-	private _onChecked = new Emitter<boolean>();
+	private readonly _onChecked = new Emitter<boolean>();
 	onChecked = this._onChecked.event;
 	_checked?: boolean;
 	get checked() {
@@ -222,17 +222,17 @@ export class QuickInputList {
 	matchOnDescription = false;
 	matchOnDetail = false;
 	matchOnLabel = true;
-	private _onChangedAllVisibleChecked = new Emitter<boolean>();
+	private readonly _onChangedAllVisibleChecked = new Emitter<boolean>();
 	onChangedAllVisibleChecked: Event<boolean> = this._onChangedAllVisibleChecked.event;
-	private _onChangedCheckedCount = new Emitter<number>();
+	private readonly _onChangedCheckedCount = new Emitter<number>();
 	onChangedCheckedCount: Event<number> = this._onChangedCheckedCount.event;
-	private _onChangedVisibleCount = new Emitter<number>();
+	private readonly _onChangedVisibleCount = new Emitter<number>();
 	onChangedVisibleCount: Event<number> = this._onChangedVisibleCount.event;
-	private _onChangedCheckedElements = new Emitter<IQuickPickItem[]>();
+	private readonly _onChangedCheckedElements = new Emitter<IQuickPickItem[]>();
 	onChangedCheckedElements: Event<IQuickPickItem[]> = this._onChangedCheckedElements.event;
-	private _onButtonTriggered = new Emitter<IQuickPickItemButtonEvent<IQuickPickItem>>();
+	private readonly _onButtonTriggered = new Emitter<IQuickPickItemButtonEvent<IQuickPickItem>>();
 	onButtonTriggered = this._onButtonTriggered.event;
-	private _onLeave = new Emitter<void>();
+	private readonly _onLeave = new Emitter<void>();
 	onLeave: Event<void> = this._onLeave.event;
 	private _fireCheckedEvents = true;
 	private elementDisposables: IDisposable[] = [];
diff --git a/src/vs/workbench/contrib/codeEditor/browser/suggestEnabledInput/suggestEnabledInput.ts b/src/vs/workbench/contrib/codeEditor/browser/suggestEnabledInput/suggestEnabledInput.ts
index 5fac853caaa..2ce7aef85f7 100644
--- a/src/vs/workbench/contrib/codeEditor/browser/suggestEnabledInput/suggestEnabledInput.ts
+++ b/src/vs/workbench/contrib/codeEditor/browser/suggestEnabledInput/suggestEnabledInput.ts
@@ -94,13 +94,13 @@ export function attachSuggestEnabledInputBoxStyler(widget: IThemable, themeServi
 
 export class SuggestEnabledInput extends Widget implements IThemable {
 
-	private _onShouldFocusResults = new Emitter<void>();
+	private readonly _onShouldFocusResults = new Emitter<void>();
 	readonly onShouldFocusResults: Event<void> = this._onShouldFocusResults.event;
 
-	private _onEnter = new Emitter<void>();
+	private readonly _onEnter = new Emitter<void>();
 	readonly onEnter: Event<void> = this._onEnter.event;
 
-	private _onInputDidChange = new Emitter<string | undefined>();
+	private readonly _onInputDidChange = new Emitter<string | undefined>();
 	readonly onInputDidChange: Event<string | undefined> = this._onInputDidChange.event;
 
 	private readonly inputWidget: CodeEditorWidget;
diff --git a/src/vs/workbench/contrib/comments/browser/commentNode.ts b/src/vs/workbench/contrib/comments/browser/commentNode.ts
index e0fce1e0ba0..e6d891f2e4f 100644
--- a/src/vs/workbench/contrib/comments/browser/commentNode.ts
+++ b/src/vs/workbench/contrib/comments/browser/commentNode.ts
@@ -57,7 +57,7 @@ export class CommentNode extends Disposable {
 	protected toolbar: ToolBar | undefined;
 	private _commentFormActions: CommentFormActions | null = null;
 
-	private _onDidDelete = new Emitter<CommentNode>();
+	private readonly _onDidDelete = new Emitter<CommentNode>();
 
 	public get domNode(): HTMLElement {
 		return this._domNode;
diff --git a/src/vs/workbench/contrib/comments/browser/commentThreadWidget.ts b/src/vs/workbench/contrib/comments/browser/commentThreadWidget.ts
index 8691a8105d5..09438e54175 100644
--- a/src/vs/workbench/contrib/comments/browser/commentThreadWidget.ts
+++ b/src/vs/workbench/contrib/comments/browser/commentThreadWidget.ts
@@ -65,8 +65,8 @@ export class ReviewZoneWidget extends ZoneWidget implements ICommentThreadWidget
 	private _commentForm: HTMLElement;
 	private _reviewThreadReplyButton: HTMLElement;
 	private _resizeObserver: any;
-	private _onDidClose = new Emitter<ReviewZoneWidget | undefined>();
-	private _onDidCreateThread = new Emitter<ReviewZoneWidget>();
+	private readonly _onDidClose = new Emitter<ReviewZoneWidget | undefined>();
+	private readonly _onDidCreateThread = new Emitter<ReviewZoneWidget>();
 	private _isExpanded?: boolean;
 	private _collapseAction: Action;
 	private _commentGlyph?: CommentGlyphWidget;
diff --git a/src/vs/workbench/contrib/debug/browser/debugConfigurationManager.ts b/src/vs/workbench/contrib/debug/browser/debugConfigurationManager.ts
index 3e71419c14a..bef32f8a8d2 100644
--- a/src/vs/workbench/contrib/debug/browser/debugConfigurationManager.ts
+++ b/src/vs/workbench/contrib/debug/browser/debugConfigurationManager.ts
@@ -50,7 +50,7 @@ export class ConfigurationManager implements IConfigurationManager {
 	private selectedName: string | undefined;
 	private selectedLaunch: ILaunch | undefined;
 	private toDispose: IDisposable[];
-	private _onDidSelectConfigurationName = new Emitter<void>();
+	private readonly _onDidSelectConfigurationName = new Emitter<void>();
 	private configProviders: IDebugConfigurationProvider[];
 	private adapterDescriptorFactories: IDebugAdapterDescriptorFactory[];
 	private debugAdapterFactories = new Map<string, IDebugAdapterFactory>();
diff --git a/src/vs/workbench/contrib/files/browser/views/explorerDecorationsProvider.ts b/src/vs/workbench/contrib/files/browser/views/explorerDecorationsProvider.ts
index eb1f7705faf..8ddcc6337d3 100644
--- a/src/vs/workbench/contrib/files/browser/views/explorerDecorationsProvider.ts
+++ b/src/vs/workbench/contrib/files/browser/views/explorerDecorationsProvider.ts
@@ -15,7 +15,7 @@ import { explorerRootErrorEmitter } from 'vs/workbench/contrib/files/browser/vie
 
 export class ExplorerDecorationsProvider implements IDecorationsProvider {
 	readonly label: string = localize('label', "Explorer");
-	private _onDidChange = new Emitter<URI[]>();
+	private readonly _onDidChange = new Emitter<URI[]>();
 	private readonly toDispose = new DisposableStore();
 
 	constructor(
diff --git a/src/vs/workbench/contrib/files/common/explorerModel.ts b/src/vs/workbench/contrib/files/common/explorerModel.ts
index 6bba996f279..161b94b12f9 100644
--- a/src/vs/workbench/contrib/files/common/explorerModel.ts
+++ b/src/vs/workbench/contrib/files/common/explorerModel.ts
@@ -21,7 +21,7 @@ export class ExplorerModel implements IDisposable {
 
 	private _roots!: ExplorerItem[];
 	private _listener: IDisposable;
-	private _onDidChangeRoots = new Emitter<void>();
+	private readonly _onDidChangeRoots = new Emitter<void>();
 
 	constructor(private readonly contextService: IWorkspaceContextService) {
 		const setRoots = () => this._roots = this.contextService.getWorkspace().folders
diff --git a/src/vs/workbench/contrib/files/common/explorerService.ts b/src/vs/workbench/contrib/files/common/explorerService.ts
index 1674c9448e1..cc957101494 100644
--- a/src/vs/workbench/contrib/files/common/explorerService.ts
+++ b/src/vs/workbench/contrib/files/common/explorerService.ts
@@ -31,11 +31,11 @@ export class ExplorerService implements IExplorerService {
 
 	private static readonly EXPLORER_FILE_CHANGES_REACT_DELAY = 500; // delay in ms to react to file changes to give our internal events a chance to react first
 
-	private _onDidChangeRoots = new Emitter<void>();
-	private _onDidChangeItem = new Emitter<{ item?: ExplorerItem, recursive: boolean }>();
-	private _onDidChangeEditable = new Emitter<ExplorerItem>();
-	private _onDidSelectResource = new Emitter<{ resource?: URI, reveal?: boolean }>();
-	private _onDidCopyItems = new Emitter<{ items: ExplorerItem[], cut: boolean, previouslyCutItems: ExplorerItem[] | undefined }>();
+	private readonly _onDidChangeRoots = new Emitter<void>();
+	private readonly _onDidChangeItem = new Emitter<{ item?: ExplorerItem, recursive: boolean }>();
+	private readonly _onDidChangeEditable = new Emitter<ExplorerItem>();
+	private readonly _onDidSelectResource = new Emitter<{ resource?: URI, reveal?: boolean }>();
+	private readonly _onDidCopyItems = new Emitter<{ items: ExplorerItem[], cut: boolean, previouslyCutItems: ExplorerItem[] | undefined }>();
 	private readonly disposables = new DisposableStore();
 	private editable: { stat: ExplorerItem, data: IEditableData } | undefined;
 	private _sortOrder: SortOrder;
diff --git a/src/vs/workbench/contrib/outline/browser/outlinePanel.ts b/src/vs/workbench/contrib/outline/browser/outlinePanel.ts
index 55ec4cb5e4b..fa20184d99d 100644
--- a/src/vs/workbench/contrib/outline/browser/outlinePanel.ts
+++ b/src/vs/workbench/contrib/outline/browser/outlinePanel.ts
@@ -169,7 +169,7 @@ class OutlineViewState {
 	private _filterOnType = true;
 	private _sortBy = OutlineSortOrder.ByKind;
 
-	private _onDidChange = new Emitter<{ followCursor?: boolean, sortBy?: boolean, filterOnType?: boolean }>();
+	private readonly _onDidChange = new Emitter<{ followCursor?: boolean, sortBy?: boolean, filterOnType?: boolean }>();
 	readonly onDidChange = this._onDidChange.event;
 
 	set followCursor(value: boolean) {
diff --git a/src/vs/workbench/contrib/scm/browser/dirtydiffDecorator.ts b/src/vs/workbench/contrib/scm/browser/dirtydiffDecorator.ts
index 7afb136e362..c7aec31036f 100644
--- a/src/vs/workbench/contrib/scm/browser/dirtydiffDecorator.ts
+++ b/src/vs/workbench/contrib/scm/browser/dirtydiffDecorator.ts
@@ -962,7 +962,7 @@ export class DirtyDiffModel extends Disposable {
 	private repositoryDisposables = new Set<IDisposable>();
 	private readonly originalModelDisposables = this._register(new DisposableStore());
 
-	private _onDidChange = new Emitter<ISplice<IChange>[]>();
+	private readonly _onDidChange = new Emitter<ISplice<IChange>[]>();
 	readonly onDidChange: Event<ISplice<IChange>[]> = this._onDidChange.event;
 
 	private _changes: IChange[] = [];
diff --git a/src/vs/workbench/contrib/scm/browser/mainPanel.ts b/src/vs/workbench/contrib/scm/browser/mainPanel.ts
index 8bad75a2aa1..134f70ce0ba 100644
--- a/src/vs/workbench/contrib/scm/browser/mainPanel.ts
+++ b/src/vs/workbench/contrib/scm/browser/mainPanel.ts
@@ -102,7 +102,7 @@ class ProviderRenderer implements IListRenderer<ISCMRepository, RepositoryTempla
 
 	readonly templateId = 'provider';
 
-	private _onDidRenderElement = new Emitter<ISCMRepository>();
+	private readonly _onDidRenderElement = new Emitter<ISCMRepository>();
 	readonly onDidRenderElement = this._onDidRenderElement.event;
 
 	constructor(
diff --git a/src/vs/workbench/contrib/scm/browser/repositoryPanel.ts b/src/vs/workbench/contrib/scm/browser/repositoryPanel.ts
index a1a17249418..6d6dadb1551 100644
--- a/src/vs/workbench/contrib/scm/browser/repositoryPanel.ts
+++ b/src/vs/workbench/contrib/scm/browser/repositoryPanel.ts
@@ -396,7 +396,7 @@ const enum ViewModelMode {
 class ViewModel {
 
 	private _mode = ViewModelMode.Tree;
-	private _onDidChangeMode = new Emitter<ViewModelMode>();
+	private readonly _onDidChangeMode = new Emitter<ViewModelMode>();
 	readonly onDidChangeMode = this._onDidChangeMode.event;
 
 	get mode(): ViewModelMode { return this._mode; }
diff --git a/src/vs/workbench/contrib/scm/browser/scmViewlet.ts b/src/vs/workbench/contrib/scm/browser/scmViewlet.ts
index 35ebbf9ccad..4ce397b202f 100644
--- a/src/vs/workbench/contrib/scm/browser/scmViewlet.ts
+++ b/src/vs/workbench/contrib/scm/browser/scmViewlet.ts
@@ -62,7 +62,7 @@ export class SCMViewlet extends ViewContainerViewlet implements IViewModel {
 	private repositoryCountKey: IContextKey<number>;
 	private viewDescriptors: RepositoryViewDescriptor[] = [];
 
-	private _onDidSplice = new Emitter<ISpliceEvent<ISCMRepository>>();
+	private readonly _onDidSplice = new Emitter<ISpliceEvent<ISCMRepository>>();
 	readonly onDidSplice: Event<ISpliceEvent<ISCMRepository>> = this._onDidSplice.event;
 
 	private _height: number | undefined = undefined;
diff --git a/src/vs/workbench/contrib/scm/common/scmService.ts b/src/vs/workbench/contrib/scm/common/scmService.ts
index d4a6da75f93..6b6583ab3ad 100644
--- a/src/vs/workbench/contrib/scm/common/scmService.ts
+++ b/src/vs/workbench/contrib/scm/common/scmService.ts
@@ -22,7 +22,7 @@ class SCMInput implements ISCMInput {
 		this._onDidChange.fire(value);
 	}
 
-	private _onDidChange = new Emitter<string>();
+	private readonly _onDidChange = new Emitter<string>();
 	readonly onDidChange: Event<string> = this._onDidChange.event;
 
 	private _placeholder = '';
@@ -36,7 +36,7 @@ class SCMInput implements ISCMInput {
 		this._onDidChangePlaceholder.fire(placeholder);
 	}
 
-	private _onDidChangePlaceholder = new Emitter<string>();
+	private readonly _onDidChangePlaceholder = new Emitter<string>();
 	readonly onDidChangePlaceholder: Event<string> = this._onDidChangePlaceholder.event;
 
 	private _visible = true;
@@ -50,7 +50,7 @@ class SCMInput implements ISCMInput {
 		this._onDidChangeVisibility.fire(visible);
 	}
 
-	private _onDidChangeVisibility = new Emitter<boolean>();
+	private readonly _onDidChangeVisibility = new Emitter<boolean>();
 	readonly onDidChangeVisibility: Event<boolean> = this._onDidChangeVisibility.event;
 
 	private _validateInput: IInputValidator = () => Promise.resolve(undefined);
@@ -64,13 +64,13 @@ class SCMInput implements ISCMInput {
 		this._onDidChangeValidateInput.fire();
 	}
 
-	private _onDidChangeValidateInput = new Emitter<void>();
+	private readonly _onDidChangeValidateInput = new Emitter<void>();
 	readonly onDidChangeValidateInput: Event<void> = this._onDidChangeValidateInput.event;
 }
 
 class SCMRepository implements ISCMRepository {
 
-	private _onDidFocus = new Emitter<void>();
+	private readonly _onDidFocus = new Emitter<void>();
 	readonly onDidFocus: Event<void> = this._onDidFocus.event;
 
 	private _selected = false;
@@ -78,7 +78,7 @@ class SCMRepository implements ISCMRepository {
 		return this._selected;
 	}
 
-	private _onDidChangeSelection = new Emitter<boolean>();
+	private readonly _onDidChangeSelection = new Emitter<boolean>();
 	readonly onDidChangeSelection: Event<boolean> = this._onDidChangeSelection.event;
 
 	readonly input: ISCMInput = new SCMInput();
@@ -114,13 +114,13 @@ export class SCMService implements ISCMService {
 	private _selectedRepositories: ISCMRepository[] = [];
 	get selectedRepositories(): ISCMRepository[] { return [...this._selectedRepositories]; }
 
-	private _onDidChangeSelectedRepositories = new Emitter<ISCMRepository[]>();
+	private readonly _onDidChangeSelectedRepositories = new Emitter<ISCMRepository[]>();
 	readonly onDidChangeSelectedRepositories: Event<ISCMRepository[]> = this._onDidChangeSelectedRepositories.event;
 
-	private _onDidAddProvider = new Emitter<ISCMRepository>();
+	private readonly _onDidAddProvider = new Emitter<ISCMRepository>();
 	readonly onDidAddRepository: Event<ISCMRepository> = this._onDidAddProvider.event;
 
-	private _onDidRemoveProvider = new Emitter<ISCMRepository>();
+	private readonly _onDidRemoveProvider = new Emitter<ISCMRepository>();
 	readonly onDidRemoveRepository: Event<ISCMRepository> = this._onDidRemoveProvider.event;
 
 	constructor(@ILogService private readonly logService: ILogService) { }
diff --git a/src/vs/workbench/services/dialogs/browser/simpleFileDialog.ts b/src/vs/workbench/services/dialogs/browser/simpleFileDialog.ts
index ee8b8925e04..ca0d3d75602 100644
--- a/src/vs/workbench/services/dialogs/browser/simpleFileDialog.ts
+++ b/src/vs/workbench/services/dialogs/browser/simpleFileDialog.ts
@@ -117,7 +117,7 @@ export class SimpleFileDialog {
 	private badPath: string | undefined;
 	private remoteAgentEnvironment: IRemoteAgentEnvironment | null | undefined;
 	private separator: string = '/';
-	private onBusyChangeEmitter = new Emitter<boolean>();
+	private readonly onBusyChangeEmitter = new Emitter<boolean>();
 	private updatingPromise: CancelablePromise<void> | undefined;
 
 	protected disposables: IDisposable[] = [
diff --git a/src/vs/workbench/services/extensionManagement/common/extensionEnablementService.ts b/src/vs/workbench/services/extensionManagement/common/extensionEnablementService.ts
index 5d98b651c5d..927b11bf516 100644
--- a/src/vs/workbench/services/extensionManagement/common/extensionEnablementService.ts
+++ b/src/vs/workbench/services/extensionManagement/common/extensionEnablementService.ts
@@ -26,7 +26,7 @@ export class ExtensionEnablementService extends Disposable implements IExtension
 
 	_serviceBrand: undefined;
 
-	private _onEnablementChanged = new Emitter<IExtension[]>();
+	private readonly _onEnablementChanged = new Emitter<IExtension[]>();
 	public readonly onEnablementChanged: Event<IExtension[]> = this._onEnablementChanged.event;
 
 	private readonly storageManger: StorageManager;
diff --git a/src/vs/workbench/test/electron-browser/textsearch.perf.integrationTest.ts b/src/vs/workbench/test/electron-browser/textsearch.perf.integrationTest.ts
index c0d3abb9cdc..88372504ee9 100644
--- a/src/vs/workbench/test/electron-browser/textsearch.perf.integrationTest.ts
+++ b/src/vs/workbench/test/electron-browser/textsearch.perf.integrationTest.ts
@@ -150,7 +150,7 @@ class TestTelemetryService implements ITelemetryService {
 
 	public events: any[] = [];
 
-	private emitter = new Emitter<any>();
+	private readonly emitter = new Emitter<any>();
 
 	public get eventLogged(): Event<any> {
 		return this.emitter.event;
diff --git a/src/vs/workbench/test/workbenchTestServices.ts b/src/vs/workbench/test/workbenchTestServices.ts
index e5ce75c7100..0cacc4e1176 100644
--- a/src/vs/workbench/test/workbenchTestServices.ts
+++ b/src/vs/workbench/test/workbenchTestServices.ts
@@ -460,8 +460,8 @@ export class TestLayoutService implements IWorkbenchLayoutService {
 	onPanelPositionChange: Event<string> = Event.None;
 	onLayout = Event.None;
 
-	private _onTitleBarVisibilityChange = new Emitter<void>();
-	private _onMenubarVisibilityChange = new Emitter<Dimension>();
+	private readonly _onTitleBarVisibilityChange = new Emitter<void>();
+	private readonly _onMenubarVisibilityChange = new Emitter<Dimension>();
 
 	public get onTitleBarVisibilityChange(): Event<void> {
 		return this._onTitleBarVisibilityChange.event;
@@ -1259,9 +1259,9 @@ export class TestLifecycleService implements ILifecycleService {
 	public phase: LifecyclePhase;
 	public startupKind: StartupKind;
 
-	private _onBeforeShutdown = new Emitter<BeforeShutdownEvent>();
-	private _onWillShutdown = new Emitter<WillShutdownEvent>();
-	private _onShutdown = new Emitter<void>();
+	private readonly _onBeforeShutdown = new Emitter<BeforeShutdownEvent>();
+	private readonly _onWillShutdown = new Emitter<WillShutdownEvent>();
+	private readonly _onShutdown = new Emitter<void>();
 
 	when(): Promise<void> {
 		return Promise.resolve();