From fbef1e18a1085e7f94561e437e2dc47e2f86a2f4 Mon Sep 17 00:00:00 2001
From: Hyden <tanxu2983@gmail.com>
Date: Sun, 5 Sep 2021 19:29:18 +0800
Subject: [PATCH 1/2] Update Object.assign to support unlimited params

Add Tuple2Intersection type, it support convert tuple to intersection. So, Object.assign can use it to define return type better.
---
 lib/lib.es2015.core.d.ts | 47 +++++++++++++++-------------------------
 1 file changed, 18 insertions(+), 29 deletions(-)

diff --git a/lib/lib.es2015.core.d.ts b/lib/lib.es2015.core.d.ts
index 79901dfe96b56..c34de0196f500 100644
--- a/lib/lib.es2015.core.d.ts
+++ b/lib/lib.es2015.core.d.ts
@@ -276,42 +276,31 @@ interface NumberConstructor {
     parseInt(string: string, radix?: number): number;
 }
 
-interface ObjectConstructor {
-    /**
-     * Copy the values of all of the enumerable own properties from one or more source objects to a
-     * target object. Returns the target object.
-     * @param target The target object to copy to.
-     * @param source The source object from which to copy properties.
-     */
-    assign<T, U>(target: T, source: U): T & U;
-
-    /**
-     * Copy the values of all of the enumerable own properties from one or more source objects to a
-     * target object. Returns the target object.
-     * @param target The target object to copy to.
-     * @param source1 The first source object from which to copy properties.
-     * @param source2 The second source object from which to copy properties.
-     */
-    assign<T, U, V>(target: T, source1: U, source2: V): T & U & V;
-
-    /**
-     * Copy the values of all of the enumerable own properties from one or more source objects to a
-     * target object. Returns the target object.
-     * @param target The target object to copy to.
-     * @param source1 The first source object from which to copy properties.
-     * @param source2 The second source object from which to copy properties.
-     * @param source3 The third source object from which to copy properties.
-     */
-    assign<T, U, V, W>(target: T, source1: U, source2: V, source3: W): T & U & V & W;
+/**
+* Return a empty object type if the param's type is undefined
+*/
+type Undefined2Object<T> = T extends undefined ? {} : T;
+
+/**
+* Remove the first tow item of tuple
+*/
+type RemoveFirstTwo<T extends unknown[], First, Second> =  T extends [a: First, b: Second, ...rest: infer P] ? P : [];
+
+/**
+* Convert tuple to intersection with tuple item's type
+*/
+type Tuple2Intersection<T extends unknown[]> = T[2] extends undefined
+  ? Undefined2Object<T[0]> & Undefined2Object<T[1]>
+  : Tuple2Intersection<[T[0], T[1]]> & Tuple2Intersection<RemoveFirstTwo<T, T[0], T[1]>>;
 
+interface ObjectConstructor {
     /**
      * Copy the values of all of the enumerable own properties from one or more source objects to a
      * target object. Returns the target object.
      * @param target The target object to copy to.
      * @param sources One or more source objects from which to copy properties
      */
-    assign(target: object, ...sources: any[]): any;
-
+    assign<T extends object, R extends object[]>(target: T, ...sources: R): Tuple2Intersection<[T, ...R]>;
     /**
      * Returns an array of all symbol properties found directly on object o.
      * @param o Object to retrieve the symbols from.

From a02422ed2a9300f7005c37c71c223af4c7e08ee2 Mon Sep 17 00:00:00 2001
From: Hyden <tanxu2983@gmail.com>
Date: Mon, 6 Sep 2021 11:11:52 +0800
Subject: [PATCH 2/2] modify the spelling

---
 lib/lib.es2015.core.d.ts | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/lib/lib.es2015.core.d.ts b/lib/lib.es2015.core.d.ts
index c34de0196f500..fa13765fb85ab 100644
--- a/lib/lib.es2015.core.d.ts
+++ b/lib/lib.es2015.core.d.ts
@@ -282,16 +282,16 @@ interface NumberConstructor {
 type Undefined2Object<T> = T extends undefined ? {} : T;
 
 /**
-* Remove the first tow item of tuple
+* Remove the first two item of tuple
 */
 type RemoveFirstTwo<T extends unknown[], First, Second> =  T extends [a: First, b: Second, ...rest: infer P] ? P : [];
 
 /**
 * Convert tuple to intersection with tuple item's type
 */
-type Tuple2Intersection<T extends unknown[]> = T[2] extends undefined
+type MergeTuple<T extends unknown[]> = T[2] extends undefined
   ? Undefined2Object<T[0]> & Undefined2Object<T[1]>
-  : Tuple2Intersection<[T[0], T[1]]> & Tuple2Intersection<RemoveFirstTwo<T, T[0], T[1]>>;
+  : MergeTuple<[T[0], T[1]]> & MergeTuple<RemoveFirstTwo<T, T[0], T[1]>>;
 
 interface ObjectConstructor {
     /**
@@ -300,7 +300,7 @@ interface ObjectConstructor {
      * @param target The target object to copy to.
      * @param sources One or more source objects from which to copy properties
      */
-    assign<T extends object, R extends object[]>(target: T, ...sources: R): Tuple2Intersection<[T, ...R]>;
+    assign<T extends object, R extends object[]>(target: T, ...sources: R): MergeTuple<[T, ...R]>;
     /**
      * Returns an array of all symbol properties found directly on object o.
      * @param o Object to retrieve the symbols from.