Lab theme augmentation instructions cause syntax error

• 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 😯

The “About the lab” docs suggest adding this line when creating the MUI theme:

import type '@material-ui/lab/themeAugmentation';

which causes error TS1005: '=' expected.

Expected Behavior 🤔

The import suggested by the docs doesn’t cause a syntax error. I’ve filed https://github.com/microsoft/TypeScript/issues/40051 to suggest this as a TypeScript feature, but in the mean time we may suggest the import be:

import '@material-ui/lab/themeAugmentation'

Your Environment 🌎

Tech	Version
Material-UI	v4.11.0
TypeScript	v3.9.7

[ianschmitz]

Actually @oliviertassinari i just discovered that import '@material-ui/lab/themeAugmentation' actually emits a runtime import which isn’t ideal. That’s by design for side-effect imports. Maybe we have a better suggestion until TypeScript possibly implements https://github.com/microsoft/TypeScript/issues/40051?

I used in my code base:

// Required to use type import, as a plain side-effect import will be emitted to runtime.
import type {} from "@material-ui/lab/themeAugmentation";

[oliviertassinari]

the instruction given in the next documentation causes #27704

@fcole90 Yeah, if you use the docs of v5, you also need to have v5 installed 😃