1 files changed, 85 insertions, 0 deletions
diff --git a/cli/dts/lib.es2019.array.d.ts b/cli/dts/lib.es2019.array.d.ts
new file mode 100644
index 000000000..160748346
--- /dev/null
+++ b/cli/dts/lib.es2019.array.d.ts
@@ -0,0 +1,85 @@
+/*! *****************************************************************************
+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"/>
+
+
+type FlatArray<Arr, Depth extends number> = {
+    "done": Arr,
+    "recur": Arr extends ReadonlyArray<infer InnerArr>
+        ? FlatArray<InnerArr, [-1, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20][Depth]>
+        : Arr
+}[Depth extends -1 ? "done" : "recur"];
+
+interface ReadonlyArray<T> {
+
+    /**
+     * Calls a defined callback function on each element of an array. Then, flattens the result into
+     * a new array.
+     * This is identical to a map followed by flat with depth 1.
+     *
+     * @param callback A function that accepts up to three arguments. The flatMap method calls the
+     * callback function one time for each element in the array.
+     * @param thisArg An object to which the this keyword can refer in the callback function. If
+     * thisArg is omitted, undefined is used as the this value.
+     */
+    flatMap<U, This = undefined> (
+        callback: (this: This, value: T, index: number, array: T[]) => U | ReadonlyArray<U>,
+        thisArg?: This
+    ): U[]
+
+
+    /**
+     * Returns a new array with all sub-array elements concatenated into it recursively up to the
+     * specified depth.
+     *
+     * @param depth The maximum recursion depth
+     */
+    flat<A, D extends number = 1>(
+        this: A,
+        depth?: D
+    ): FlatArray<A, D>[]
+  }
+
+interface Array<T> {
+
+    /**
+     * Calls a defined callback function on each element of an array. Then, flattens the result into
+     * a new array.
+     * This is identical to a map followed by flat with depth 1.
+     *
+     * @param callback A function that accepts up to three arguments. The flatMap method calls the
+     * callback function one time for each element in the array.
+     * @param thisArg An object to which the this keyword can refer in the callback function. If
+     * thisArg is omitted, undefined is used as the this value.
+     */
+    flatMap<U, This = undefined> (
+        callback: (this: This, value: T, index: number, array: T[]) => U | ReadonlyArray<U>,
+        thisArg?: This
+    ): U[]
+
+    /**
+     * Returns a new array with all sub-array elements concatenated into it recursively up to the
+     * specified depth.
+     *
+     * @param depth The maximum recursion depth
+     */
+    flat<A, D extends number = 1>(
+        this: A,
+        depth?: D
+    ): FlatArray<A, D>[]
+}