Incorrect TypeScript definition of `createStyles()`

[JasonHK]

• The issue is present in the latest release.
• I have searched the issues of this repository and believe that this is not a duplicate.

Current Behavior 😯

According to the documentation, createStyles() should accept either a function or an object, but the TypeScript definition accept an object only.

Expected Behavior 🤔

The TypeScript definition of createStyles() should also accept a function.

Steps to Reproduce 🕹

CodeSandbox reproduction: https://codesandbox.io/s/sparkling-moon-yrppz?file=/src/index.ts

Context 🔦

Your Environment 🌎

Tech	Version
Material-UI	v4.9.12
React	N/A
Browser	N/A
TypeScript	v3.8.3
etc.

[eps1lon]

createStyles<IStylesClassKey, IStylesProps>(() => {

We don't accept a function without an argument. The function signature is only useful if you're using the theme:

-createStyles<IStylesClassKey, IStylesProps>(() => {
+createStyles<IStylesClassKey, IStylesProps>(theme => {

[JasonHK]

createStyles<IStylesClassKey, IStylesProps>(() => {

We don't accept a function without an argument. The function signature is only useful if you're using the theme:

-createStyles<IStylesClassKey, IStylesProps>(() => {
+createStyles<IStylesClassKey, IStylesProps>(theme => {

@eps1lon No, TypeScript STILL throws an error after adding the argument. TypeScript doesn't care if the arguments were omitted or not.

Don't you read the description of the issue?

Current Behavior 😯

According to the documentation, createStyles() should accept either a function or an object, but the TypeScript definition accept an object only.

[JasonHK]

@eps1lon Is this what you called "working properly"?

[eps1lon]

Right, the API docs are wrong. See our TypeScript guide for the correct usage of createStyles