From ac5c2068c43ee6982552d51468b1e48b56557b40 Mon Sep 17 00:00:00 2001
From: Sebastian Silbermann <silbermann.sebastian@gmail.com>
Date: Sun, 22 Nov 2020 11:02:59 +0100
Subject: [PATCH] [core] Add support for TypeScript 4.1 (#23633)

---
 package.json                                  |  2 +-
 .../src/makeStyles/makeStyles.d.ts            | 19 ++++++-------------
 .../src/makeStyles/makeStyles.spec.tsx        |  2 +-
 packages/material-ui-utils/src/deepmerge.ts   |  8 +++++++-
 .../material-ui/src/styles/makeStyles.d.ts    | 18 ++++++------------
 5 files changed, 21 insertions(+), 28 deletions(-)

diff --git a/package.json b/package.json
index 0ae0184a14c00e..d6dc9369deff2e 100644
--- a/package.json
+++ b/package.json
@@ -49,7 +49,7 @@
     "test:umd": "node packages/material-ui/test/umd/run.js",
     "test:unit": "cross-env NODE_ENV=test mocha 'packages/**/*.test.{js,ts,tsx}' 'docs/**/*.test.{js,ts,tsx}' 'scripts/**/*.test.{js,ts,tsx}' 'test/utils/**/*.test.{js,ts,tsx}'",
     "test:watch": "yarn test:unit --watch",
-    "typescript": "lerna run typescript --parallel"
+    "typescript": "lerna run --no-bail --parallel typescript"
   },
   "devDependencies": {
     "@babel/cli": "^7.10.1",
diff --git a/packages/material-ui-styles/src/makeStyles/makeStyles.d.ts b/packages/material-ui-styles/src/makeStyles/makeStyles.d.ts
index a0ce04b43fcde1..b164e38cd7e3c4 100644
--- a/packages/material-ui-styles/src/makeStyles/makeStyles.d.ts
+++ b/packages/material-ui-styles/src/makeStyles/makeStyles.d.ts
@@ -2,22 +2,15 @@ import { ClassNameMap, Styles, WithStylesOptions } from '@material-ui/styles/wit
 import { Omit } from '@material-ui/types';
 import { DefaultTheme } from '../defaultTheme';
 
-/**
- * `makeStyles` where the passed `styles` do not depend on props
- */
-export default function makeStyles<Theme = DefaultTheme, ClassKey extends string = string>(
-  style: Styles<Theme, {}, ClassKey>,
-  options?: Omit<WithStylesOptions<Theme>, 'withTheme'>
-): (props?: any) => ClassNameMap<ClassKey>;
-
-/**
- * `makeStyles` where the passed `styles` do depend on props
- */
 export default function makeStyles<
   Theme = DefaultTheme,
-  Props extends {} = {},
+  Props extends object = {},
   ClassKey extends string = string
 >(
   styles: Styles<Theme, Props, ClassKey>,
   options?: Omit<WithStylesOptions<Theme>, 'withTheme'>
-): (props: Props) => ClassNameMap<ClassKey>;
+): keyof Props extends never
+  ? // `makeStyles` where the passed `styles` do not depend on props
+    (props?: any) => ClassNameMap<ClassKey>
+  : // `makeStyles` where the passed `styles` do depend on props
+    (props: Props) => ClassNameMap<ClassKey>;
diff --git a/packages/material-ui-styles/src/makeStyles/makeStyles.spec.tsx b/packages/material-ui-styles/src/makeStyles/makeStyles.spec.tsx
index 0ec32547be1d70..c8e00982f2a567 100644
--- a/packages/material-ui-styles/src/makeStyles/makeStyles.spec.tsx
+++ b/packages/material-ui-styles/src/makeStyles/makeStyles.spec.tsx
@@ -81,7 +81,7 @@ import { createStyles, makeStyles } from '@material-ui/styles';
   );
 
   const UnsafeProps = (props: StyleProps) => {
-    // would be nice to have at least a compile time error because we forgot the argument
+    // @ts-expect-error
     const classes = useUnsafeProps(); // runtime: Can't read property color of undefined
     // but this would pass anyway
     const alsoClasses = useUnsafeProps(undefined); // runtime: Can't read property color of undefined
diff --git a/packages/material-ui-utils/src/deepmerge.ts b/packages/material-ui-utils/src/deepmerge.ts
index 3952225a06f2fa..8ff8d1c26ab3eb 100644
--- a/packages/material-ui-utils/src/deepmerge.ts
+++ b/packages/material-ui-utils/src/deepmerge.ts
@@ -1,5 +1,11 @@
 export function isPlainObject(item: unknown): item is Record<keyof any, unknown> {
-  return item && typeof item === 'object' && item.constructor === Object;
+  return (
+    item !== null &&
+    typeof item === 'object' &&
+    // TS thinks `item is possibly null` even though this was our first guard.
+    // @ts-expect-error
+    item.constructor === Object
+  );
 }
 
 export interface DeepmergeOptions {
diff --git a/packages/material-ui/src/styles/makeStyles.d.ts b/packages/material-ui/src/styles/makeStyles.d.ts
index 07908af194078f..1f8218efa0a9da 100644
--- a/packages/material-ui/src/styles/makeStyles.d.ts
+++ b/packages/material-ui/src/styles/makeStyles.d.ts
@@ -2,21 +2,15 @@ import { ClassNameMap, Styles, WithStylesOptions } from '@material-ui/styles/wit
 import { Omit } from '@material-ui/types';
 import { Theme as DefaultTheme } from './createMuiTheme';
 
-/**
- * `makeStyles` where the passed `styles` do not depend on props
- */
-export default function makeStyles<Theme = DefaultTheme, ClassKey extends string = string>(
-  style: Styles<Theme, {}, ClassKey>,
-  options?: Omit<WithStylesOptions<Theme>, 'withTheme'>
-): (props?: any) => ClassNameMap<ClassKey>;
-/**
- * `makeStyles` where the passed `styles` do depend on props
- */
 export default function makeStyles<
   Theme = DefaultTheme,
-  Props extends {} = {},
+  Props extends object = {},
   ClassKey extends string = string
 >(
   styles: Styles<Theme, Props, ClassKey>,
   options?: Omit<WithStylesOptions<Theme>, 'withTheme'>
-): (props: Props) => ClassNameMap<ClassKey>;
+): keyof Props extends never
+  ? // `makeStyles` where the passed `styles` do not depend on props
+    (props?: any) => ClassNameMap<ClassKey>
+  : // `makeStyles` where the passed `styles` do depend on props
+    (props: Props) => ClassNameMap<ClassKey>;