1 files changed, 29 insertions, 0 deletions
diff --git a/cli/tsc/dts/lib.esnext.collection.d.ts b/cli/tsc/dts/lib.esnext.collection.d.ts
new file mode 100644
index 000000000..a48fd93d5
--- /dev/null
+++ b/cli/tsc/dts/lib.esnext.collection.d.ts
@@ -0,0 +1,29 @@
+/*! *****************************************************************************
+Copyright (c) Microsoft Corporation. All rights reserved.
+Licensed under the Apache License, Version 2.0 (the "License"); you may not use
+this file except in compliance with the License. You may obtain a copy of the
+License at http://www.apache.org/licenses/LICENSE-2.0
+
+THIS CODE IS PROVIDED ON AN *AS IS* BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+KIND, EITHER EXPRESS OR IMPLIED, INCLUDING WITHOUT LIMITATION ANY IMPLIED
+WARRANTIES OR CONDITIONS OF TITLE, FITNESS FOR A PARTICULAR PURPOSE,
+MERCHANTABLITY OR NON-INFRINGEMENT.
+
+See the Apache Version 2.0 License for specific language governing permissions
+and limitations under the License.
+***************************************************************************** */
+
+
+/// <reference no-default-lib="true"/>
+
+interface MapConstructor {
+    /**
+     * Groups members of an iterable according to the return value of the passed callback.
+     * @param items An iterable.
+     * @param keySelector A callback which will be invoked for each item in items.
+     */
+    groupBy<K, T>(
+        items: Iterable<T>,
+        keySelector: (item: T, index: number) => K,
+    ): Map<K, T[]>;
+}