diff --git a/src/vs/base/browser/ui/tree/abstractTree.ts b/src/vs/base/browser/ui/tree/abstractTree.ts
index 3c7aa3ad308..1a5f138db2f 100644
--- a/src/vs/base/browser/ui/tree/abstractTree.ts
+++ b/src/vs/base/browser/ui/tree/abstractTree.ts
@@ -22,7 +22,7 @@ import { distinct, equals, firstOrDefault, range } from 'vs/base/common/arrays';
 import { Delayer, disposableTimeout, timeout } from 'vs/base/common/async';
 import { Codicon } from 'vs/base/common/codicons';
 import { ThemeIcon } from 'vs/base/common/themables';
-import { SetMap } from 'vs/base/common/collections';
+import { SetMap } from 'vs/base/common/map';
 import { Emitter, Event, EventBufferer, Relay } from 'vs/base/common/event';
 import { fuzzyScore, FuzzyScore } from 'vs/base/common/filters';
 import { KeyCode } from 'vs/base/common/keyCodes';
diff --git a/src/vs/base/common/collections.ts b/src/vs/base/common/collections.ts
index 4ff9b49829c..0b306144e5e 100644
--- a/src/vs/base/common/collections.ts
+++ b/src/vs/base/common/collections.ts
@@ -80,51 +80,3 @@ export function intersection<T>(setA: Set<T>, setB: Iterable<T>): Set<T> {
 	}
 	return result;
 }
-
-export class SetMap<K, V> {
-
-	private map = new Map<K, Set<V>>();
-
-	add(key: K, value: V): void {
-		let values = this.map.get(key);
-
-		if (!values) {
-			values = new Set<V>();
-			this.map.set(key, values);
-		}
-
-		values.add(value);
-	}
-
-	delete(key: K, value: V): void {
-		const values = this.map.get(key);
-
-		if (!values) {
-			return;
-		}
-
-		values.delete(value);
-
-		if (values.size === 0) {
-			this.map.delete(key);
-		}
-	}
-
-	forEach(key: K, fn: (value: V) => void): void {
-		const values = this.map.get(key);
-
-		if (!values) {
-			return;
-		}
-
-		values.forEach(fn);
-	}
-
-	get(key: K): ReadonlySet<V> {
-		const values = this.map.get(key);
-		if (!values) {
-			return new Set<V>();
-		}
-		return values;
-	}
-}
diff --git a/src/vs/base/common/lifecycle.ts b/src/vs/base/common/lifecycle.ts
index a1aa7f2bd66..9dff9590abb 100644
--- a/src/vs/base/common/lifecycle.ts
+++ b/src/vs/base/common/lifecycle.ts
@@ -4,7 +4,8 @@
  *--------------------------------------------------------------------------------------------*/
 
 import { compareBy, numberComparator } from 'vs/base/common/arrays';
-import { SetMap, groupBy } from 'vs/base/common/collections';
+import { groupBy } from 'vs/base/common/collections';
+import { SetMap } from './map';
 import { createSingleCallFunction } from 'vs/base/common/functional';
 import { Iterable } from 'vs/base/common/iterator';
 
diff --git a/src/vs/base/common/map.ts b/src/vs/base/common/map.ts
index 74fd108e399..9249bf9af0c 100644
--- a/src/vs/base/common/map.ts
+++ b/src/vs/base/common/map.ts
@@ -742,3 +742,51 @@ export class BidirectionalMap<K, V> {
 		return this._m1.values();
 	}
 }
+
+export class SetMap<K, V> {
+
+	private map = new Map<K, Set<V>>();
+
+	add(key: K, value: V): void {
+		let values = this.map.get(key);
+
+		if (!values) {
+			values = new Set<V>();
+			this.map.set(key, values);
+		}
+
+		values.add(value);
+	}
+
+	delete(key: K, value: V): void {
+		const values = this.map.get(key);
+
+		if (!values) {
+			return;
+		}
+
+		values.delete(value);
+
+		if (values.size === 0) {
+			this.map.delete(key);
+		}
+	}
+
+	forEach(key: K, fn: (value: V) => void): void {
+		const values = this.map.get(key);
+
+		if (!values) {
+			return;
+		}
+
+		values.forEach(fn);
+	}
+
+	get(key: K): ReadonlySet<V> {
+		const values = this.map.get(key);
+		if (!values) {
+			return new Set<V>();
+		}
+		return values;
+	}
+}
diff --git a/src/vs/base/test/common/map.test.ts b/src/vs/base/test/common/map.test.ts
index e8cfca7d714..8793b24dcd1 100644
--- a/src/vs/base/test/common/map.test.ts
+++ b/src/vs/base/test/common/map.test.ts
@@ -4,7 +4,7 @@
  *--------------------------------------------------------------------------------------------*/
 
 import * as assert from 'assert';
-import { BidirectionalMap, LinkedMap, LRUCache, ResourceMap, Touch } from 'vs/base/common/map';
+import { BidirectionalMap, LinkedMap, LRUCache, ResourceMap, SetMap, Touch } from 'vs/base/common/map';
 import { extUriIgnorePathCase } from 'vs/base/common/resources';
 import { URI } from 'vs/base/common/uri';
 
@@ -571,3 +571,42 @@ suite('BidirectionalMap', () => {
 		assert.strictEqual(map.getKey(3), undefined);
 	});
 });
+
+suite('SetMap', () => {
+
+	test('add and get', () => {
+		const setMap = new SetMap<string, number>();
+		setMap.add('a', 1);
+		setMap.add('a', 2);
+		setMap.add('b', 3);
+		assert.deepStrictEqual([...setMap.get('a')], [1, 2]);
+		assert.deepStrictEqual([...setMap.get('b')], [3]);
+	});
+
+	test('delete', () => {
+		const setMap = new SetMap<string, number>();
+		setMap.add('a', 1);
+		setMap.add('a', 2);
+		setMap.add('b', 3);
+		setMap.delete('a', 1);
+		assert.deepStrictEqual([...setMap.get('a')], [2]);
+		setMap.delete('a', 2);
+		assert.deepStrictEqual([...setMap.get('a')], []);
+	});
+
+	test('forEach', () => {
+		const setMap = new SetMap<string, number>();
+		setMap.add('a', 1);
+		setMap.add('a', 2);
+		setMap.add('b', 3);
+		let sum = 0;
+		setMap.forEach('a', value => sum += value);
+		assert.strictEqual(sum, 3);
+	});
+
+	test('get empty set', () => {
+		const setMap = new SetMap<string, number>();
+		assert.deepStrictEqual([...setMap.get('a')], []);
+	});
+
+});
diff --git a/src/vs/editor/common/diff/defaultLinesDiffComputer/computeMovedLines.ts b/src/vs/editor/common/diff/defaultLinesDiffComputer/computeMovedLines.ts
index 2d25234c4e5..75ad5f23d52 100644
--- a/src/vs/editor/common/diff/defaultLinesDiffComputer/computeMovedLines.ts
+++ b/src/vs/editor/common/diff/defaultLinesDiffComputer/computeMovedLines.ts
@@ -7,7 +7,7 @@ import { ITimeout, SequenceDiff } from 'vs/editor/common/diff/defaultLinesDiffCo
 import { DetailedLineRangeMapping, LineRangeMapping } from '../rangeMapping';
 import { pushMany, compareBy, numberComparator, reverseOrder } from 'vs/base/common/arrays';
 import { MonotonousArray, findLastMonotonous } from 'vs/base/common/arraysFind';
-import { SetMap } from 'vs/base/common/collections';
+import { SetMap } from 'vs/base/common/map';
 import { LineRange, LineRangeSet } from 'vs/editor/common/core/lineRange';
 import { OffsetRange } from 'vs/editor/common/core/offsetRange';
 import { LinesSliceCharSequence } from 'vs/editor/common/diff/defaultLinesDiffComputer/linesSliceCharSequence';
diff --git a/src/vs/editor/contrib/inlineCompletions/browser/provideInlineCompletions.ts b/src/vs/editor/contrib/inlineCompletions/browser/provideInlineCompletions.ts
index a9952a50f14..9d91e0ade1e 100644
--- a/src/vs/editor/contrib/inlineCompletions/browser/provideInlineCompletions.ts
+++ b/src/vs/editor/contrib/inlineCompletions/browser/provideInlineCompletions.ts
@@ -6,7 +6,7 @@
 import { assertNever } from 'vs/base/common/assert';
 import { DeferredPromise } from 'vs/base/common/async';
 import { CancellationToken } from 'vs/base/common/cancellation';
-import { SetMap } from 'vs/base/common/collections';
+import { SetMap } from 'vs/base/common/map';
 import { onUnexpectedExternalError } from 'vs/base/common/errors';
 import { IDisposable } from 'vs/base/common/lifecycle';
 import { ISingleEditOperation } from 'vs/editor/common/core/editOperation';
diff --git a/src/vs/workbench/common/views.ts b/src/vs/workbench/common/views.ts
index 8633aac784a..84cee2b04a6 100644
--- a/src/vs/workbench/common/views.ts
+++ b/src/vs/workbench/common/views.ts
@@ -11,13 +11,12 @@ import { localize } from 'vs/nls';
 import { createDecorator } from 'vs/platform/instantiation/common/instantiation';
 import { IDisposable, Disposable, toDisposable } from 'vs/base/common/lifecycle';
 import { ThemeIcon } from 'vs/base/common/themables';
-import { getOrSet } from 'vs/base/common/map';
+import { getOrSet, SetMap } from 'vs/base/common/map';
 import { Registry } from 'vs/platform/registry/common/platform';
 import { IKeybindings } from 'vs/platform/keybinding/common/keybindingsRegistry';
 import { ExtensionIdentifier } from 'vs/platform/extensions/common/extensions';
 import { flatten } from 'vs/base/common/arrays';
 import { SyncDescriptor } from 'vs/platform/instantiation/common/descriptors';
-import { SetMap } from 'vs/base/common/collections';
 import { IProgressIndicator } from 'vs/platform/progress/common/progress';
 import Severity from 'vs/base/common/severity';
 import { IPaneComposite } from 'vs/workbench/common/panecomposite';