diff --git a/src/vs/base/common/map.ts b/src/vs/base/common/map.ts
index eee70e82684106f9cebf30e9db740f9fb31e73f5..277ab50bb88d962f1e4ed01b77ddfa0b7037ee94 100644
--- a/src/vs/base/common/map.ts
+++ b/src/vs/base/common/map.ts
@@ -8,14 +8,6 @@ import { CharCode } from 'vs/base/common/charCode';
 import { Iterator, IteratorResult, FIN } from './iterator';
 
 
-export function fromArray<T>(array: readonly T[]): Set<T> {
-	const result = new Set<T>();
-	for (const element of array) {
-		result.add(element);
-	}
-	return result;
-}
-
 export function values<V = any>(set: Set<V>): V[];
 export function values<K = any, V = any>(map: Map<K, V>): V[];
 export function values<V>(forEachable: { forEach(callback: (value: V, ...more: any[]) => any): void }): V[] {
diff --git a/src/vs/editor/common/modes.ts b/src/vs/editor/common/modes.ts
index 9bf53989111b64636be2a196500ffd96f637ee7d..b5428b8840339fd7255b3894cbbfbadedb1123a1 100644
--- a/src/vs/editor/common/modes.ts
+++ b/src/vs/editor/common/modes.ts
@@ -404,7 +404,7 @@ export interface CompletionItem {
 	 * A modifier to the `kind` which affect how the item
 	 * is rendered, e.g. Deprecated is rendered with a strikeout
 	 */
-	kindTags?: Set<CompletionItemKindTag>;
+	kindTags?: ReadonlyArray<CompletionItemKindTag>;
 	/**
 	 * A human-readable string with additional information
 	 * about this item, like type or symbol information.
@@ -913,7 +913,7 @@ export interface DocumentSymbol {
 	name: string;
 	detail: string;
 	kind: SymbolKind;
-	kindTags: SymbolKindTag[];
+	kindTags: ReadonlyArray<SymbolKindTag>;
 	containerName?: string;
 	range: IRange;
 	selectionRange: IRange;
diff --git a/src/vs/editor/contrib/suggest/suggestWidget.ts b/src/vs/editor/contrib/suggest/suggestWidget.ts
index cb0260ecc609aa04f6bbd4409f1b727aa98afbce..8a0c10b205c4b94443d6604874580328e849ea4b 100644
--- a/src/vs/editor/contrib/suggest/suggestWidget.ts
+++ b/src/vs/editor/contrib/suggest/suggestWidget.ts
@@ -193,7 +193,7 @@ class Renderer implements IListRenderer<CompletionItem, ISuggestionTemplateData>
 			];
 		}
 
-		if (suggestion.kindTags && suggestion.kindTags.has(CompletionItemKindTag.Deprecated)) {
+		if (suggestion.kindTags && suggestion.kindTags.indexOf(CompletionItemKindTag.Deprecated) >= 0) {
 			labelOptions.extraClasses = (labelOptions.extraClasses || []).concat(['deprecated']);
 			labelOptions.matches = [];
 		}
diff --git a/src/vs/monaco.d.ts b/src/vs/monaco.d.ts
index 79c36b8b67e426f824e3a1962dd13e54f00ab955..b55c54c2aa4d9e1192bd8dcd2c4a2fecb5a7b78e 100644
--- a/src/vs/monaco.d.ts
+++ b/src/vs/monaco.d.ts
@@ -4822,7 +4822,7 @@ declare namespace monaco.languages {
 		 * A modifier to the `kind` which affect how the item
 		 * is rendered, e.g. Deprecated is rendered with a strikeout
 		 */
-		kindTags?: Set<CompletionItemKindTag>;
+		kindTags?: ReadonlyArray<CompletionItemKindTag>;
 		/**
 		 * A human-readable string with additional information
 		 * about this item, like type or symbol information.
@@ -5240,7 +5240,7 @@ declare namespace monaco.languages {
 		name: string;
 		detail: string;
 		kind: SymbolKind;
-		kindTags: SymbolKindTag[];
+		kindTags: ReadonlyArray<SymbolKindTag>;
 		containerName?: string;
 		range: IRange;
 		selectionRange: IRange;
diff --git a/src/vs/workbench/api/browser/mainThreadLanguageFeatures.ts b/src/vs/workbench/api/browser/mainThreadLanguageFeatures.ts
index cbc61e52916a450910ff016972fef6d56cb94df0..d9c397890d062f100c4476dc3d70d92af05afe57 100644
--- a/src/vs/workbench/api/browser/mainThreadLanguageFeatures.ts
+++ b/src/vs/workbench/api/browser/mainThreadLanguageFeatures.ts
@@ -21,7 +21,6 @@ import { Selection } from 'vs/editor/common/core/selection';
 import { ExtensionIdentifier } from 'vs/platform/extensions/common/extensions';
 import * as callh from 'vs/workbench/contrib/callHierarchy/common/callHierarchy';
 import { mixin } from 'vs/base/common/objects';
-import { fromArray } from 'vs/base/common/map';
 
 @extHostNamedCustomer(MainContext.MainThreadLanguageFeatures)
 export class MainThreadLanguageFeatures implements MainThreadLanguageFeaturesShape {
@@ -331,7 +330,7 @@ export class MainThreadLanguageFeatures implements MainThreadLanguageFeaturesSha
 		return {
 			label: data.a,
 			kind: data.b,
-			kindTags: data.n && fromArray(data.n),
+			kindTags: data.n,
 			detail: data.c,
 			documentation: data.d,
 			sortText: data.e,