From e4e23898686532d9dcfa025341075ebb77ce9d84 Mon Sep 17 00:00:00 2001
From: EnixCoda <enixcoda@gmail.com>
Date: Wed, 20 Feb 2019 12:30:20 +0800
Subject: [PATCH] fix: return type of $

---
 src/components/Portal.tsx  |  2 +-
 src/driver/core/SideBar.ts |  2 +-
 src/utils/DOMHelper.ts     | 14 ++++++++++----
 3 files changed, 12 insertions(+), 6 deletions(-)

diff --git a/src/components/Portal.tsx b/src/components/Portal.tsx
index 8af7152..2747871 100644
--- a/src/components/Portal.tsx
+++ b/src/components/Portal.tsx
@@ -2,7 +2,7 @@ import * as React from 'react'
 import * as ReactDOM from 'react-dom'
 
 type Props = {
-  into: HTMLElement
+  into: Element
 }
 
 class Portal extends React.PureComponent<Props> {
diff --git a/src/driver/core/SideBar.ts b/src/driver/core/SideBar.ts
index 02a601a..ee76bce 100644
--- a/src/driver/core/SideBar.ts
+++ b/src/driver/core/SideBar.ts
@@ -37,7 +37,7 @@ export type ConnectorState = {
   compressSingletonFolder?: boolean
   copyFileButton?: boolean
   copySnippetButton?: boolean
-  logoContainerElement: HTMLElement | null
+  logoContainerElement: Element | null
 
   init: () => void
   onPJAXEnd: () => void
diff --git a/src/utils/DOMHelper.ts b/src/utils/DOMHelper.ts
index db08765..f1936ec 100644
--- a/src/utils/DOMHelper.ts
+++ b/src/utils/DOMHelper.ts
@@ -28,11 +28,17 @@ function setBodyIndent(shouldShowGitako: boolean) {
   }
 }
 
-function $<R1 = never, R2 = never>(
+function $<E extends (element: Element) => any, O extends () => any>(
   selector: string,
-  existCallback?: (element: Element) => R1,
-  otherwise?: () => R2,
-): R1 | R2 | Element {
+  existCallback?: E,
+  otherwise?: O,
+): E extends never
+  ? O extends never
+    ? (Element | null)
+    : ReturnType<O> | null
+  : O extends never
+  ? (ReturnType<E> | null)
+  : ReturnType<O> | ReturnType<E> {
   const element = document.querySelector(selector)
   if (element) {
     return existCallback ? existCallback(element) : element