From f67d09b28ed5f1b0185b1a72408f0a24734f9d82 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Chiciuc=20Nicu=C8=99or?= <nicuchiciuc@gmail.com>
Date: Sat, 4 Apr 2020 07:32:56 +0300
Subject: [PATCH] fix: Extract type of the element of a tuple without indexing.
 (#22916)

* Extract type of the element of a tuple without indexing.

* Amend ElementOf<T> to also support readonly arrays.
---
 components/_util/type.ts               | 6 ++++++
 components/transfer/renderListBody.tsx | 4 ++--
 2 files changed, 8 insertions(+), 2 deletions(-)

diff --git a/components/_util/type.ts b/components/_util/type.ts
index 7e3f82bd0ed8..7620c9db1cd4 100644
--- a/components/_util/type.ts
+++ b/components/_util/type.ts
@@ -3,3 +3,9 @@ export type Omit<T, K extends keyof T> = Pick<T, Exclude<keyof T, K>>;
 export const tuple = <T extends string[]>(...args: T) => args;
 
 export const tupleNum = <T extends number[]>(...args: T) => args;
+
+/**
+ * https://stackoverflow.com/a/59187769
+ * Extract the type of an element of an array/tuple without performing indexing
+ */
+export type ElementOf<T> = T extends (infer E)[] ? E : T extends readonly (infer E)[] ? E : never;
diff --git a/components/transfer/renderListBody.tsx b/components/transfer/renderListBody.tsx
index 792f4ec93364..3c065bff1f63 100644
--- a/components/transfer/renderListBody.tsx
+++ b/components/transfer/renderListBody.tsx
@@ -1,11 +1,11 @@
 import * as React from 'react';
-import { Omit, tuple } from '../_util/type';
+import { ElementOf, Omit, tuple } from '../_util/type';
 import { TransferItem } from '.';
 import { TransferListProps, RenderedItem } from './list';
 import ListItem from './ListItem';
 
 export const OmitProps = tuple('handleFilter', 'handleClear', 'checkedKeys');
-export type OmitProp = typeof OmitProps[number];
+export type OmitProp = ElementOf<typeof OmitProps>;
 type PartialTransferListProps = Omit<TransferListProps, OmitProp>;
 
 export interface TransferListBodyProps extends PartialTransferListProps {