make Array explicitly extend ReadonlyArray and use this type in the callbacks

src/lib/es2015.core.d.ts

@@ -1,26 +1,4 @@
-interface Array<T> {
-    /**
-     * Returns the value of the first element in the array where predicate is true, and undefined
-     * otherwise.
-     * @param predicate find calls predicate once for each element of the array, in ascending
-     * order, until it finds one where predicate returns true. If such an element is found, find
-     * immediately returns that element value. Otherwise, find returns undefined.
-     * @param thisArg If provided, it will be used as the this value for each invocation of
-     * predicate. If it is not provided, undefined is used instead.
-     */
-    find<S extends T>(predicate: (this: void, value: T, index: number, obj: T[]) => value is S, thisArg?: any): S | undefined;
-    find(predicate: (value: T, index: number, obj: T[]) => unknown, thisArg?: any): T | undefined;
-
-    /**
-     * Returns the index of the first element in the array where predicate is true, and -1
-     * otherwise.
-     * @param predicate find calls predicate once for each element of the array, in ascending
-     * order, until it finds one where predicate returns true. If such an element is found,
-     * findIndex immediately returns that element index. Otherwise, findIndex returns -1.
-     * @param thisArg If provided, it will be used as the this value for each invocation of
-     * predicate. If it is not provided, undefined is used instead.
-     */
-    findIndex(predicate: (value: T, index: number, obj: T[]) => unknown, thisArg?: any): number;
+interface Array<T> extends ReadonlyArray<T> {
 
     /**
      * Changes all array elements from `start` to `end` index to a static `value` and returns the modified array
@@ -329,8 +307,8 @@ interface ReadonlyArray<T> {
      * @param thisArg If provided, it will be used as the this value for each invocation of
      * predicate. If it is not provided, undefined is used instead.
      */
-    find<S extends T>(predicate: (this: void, value: T, index: number, obj: readonly T[]) => value is S, thisArg?: any): S | undefined;
-    find(predicate: (value: T, index: number, obj: readonly T[]) => unknown, thisArg?: any): T | undefined;
+    find<S extends T>(predicate: (this: void, value: T, index: number, obj: this) => value is S, thisArg?: any): S | undefined;
+    find(predicate: (value: T, index: number, obj: this) => unknown, thisArg?: any): T | undefined;
 
     /**
      * Returns the index of the first element in the array where predicate is true, and -1
@@ -341,7 +319,7 @@ interface ReadonlyArray<T> {
      * @param thisArg If provided, it will be used as the this value for each invocation of
      * predicate. If it is not provided, undefined is used instead.
      */
-    findIndex(predicate: (value: T, index: number, obj: readonly T[]) => unknown, thisArg?: any): number;
+    findIndex(predicate: (value: T, index: number, obj: this) => unknown, thisArg?: any): number;
 }
 
 interface RegExp {

src/lib/es2015.iterable.d.ts

@@ -35,26 +35,6 @@ interface IterableIterator<T> extends Iterator<T> {
     [Symbol.iterator](): IterableIterator<T>;
 }
 
-interface Array<T> {
-    /** Iterator */
-    [Symbol.iterator](): IterableIterator<T>;
-
-    /**
-     * Returns an iterable of key, value pairs for every entry in the array
-     */
-    entries(): IterableIterator<[number, T]>;
-
-    /**
-     * Returns an iterable of keys in the array
-     */
-    keys(): IterableIterator<number>;
-
-    /**
-     * Returns an iterable of values in the array
-     */
-    values(): IterableIterator<T>;
-}
-
 interface ArrayConstructor {
     /**
      * Creates an array from an iterable object.

src/lib/es2015.symbol.wellknown.d.ts

@@ -71,7 +71,7 @@ interface Symbol {
     readonly [Symbol.toStringTag]: string;
 }
 
-interface Array<T> {
+interface Array<T> extends ReadonlyArray<T> {
     /**
      * Returns an object whose properties have the value 'true'
      * when they will be absent when used in a 'with' statement.

src/lib/es2016.array.include.d.ts

@@ -1,12 +1,3 @@
-interface Array<T> {
-    /**
-     * Determines whether an array includes a certain element, returning true or false as appropriate.
-     * @param searchElement The element to search for.
-     * @param fromIndex The position in this array at which to begin searching for searchElement.
-     */
-    includes(searchElement: T, fromIndex?: number): boolean;
-}
-
 interface ReadonlyArray<T> {
     /**
      * Determines whether an array includes a certain element, returning true or false as appropriate.

src/lib/es2019.array.d.ts

@@ -23,35 +23,6 @@ interface ReadonlyArray<T> {
     ): 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.

src/lib/es2022.array.d.ts

@@ -1,11 +1,3 @@
-interface Array<T> {
-    /**
-     * Returns the item located at the specified index.
-     * @param index The zero-based index of the desired code unit. A negative index will count back from the last item.
-     */
-    at(index: number): T | undefined;
-}
-
 interface ReadonlyArray<T> {
     /**
      * Returns the item located at the specified index.