[core] Update typings for theme's components

[mnajdova]

Updates the theme.components.styleOverrides and theme.components.variants to use the same typigns for the styles as the experimentalStyled().

[mui-pr-bot]

No bundle size changes

Generated by 🚫 dangerJS against ded02ef

[oliviertassinari]

As a side note (of the scope of the PR). There might be something to consider regarding PropsFunc. It's currently not implemented but the type accepts it: https://codesandbox.io/s/globalthemeoverride-material-demo-forked-x099w?file=/demo.tsx.

import * as React from "react";
import { ThemeProvider, createMuiTheme } from "@material-ui/core/styles";
import Button from "@material-ui/core/Button";

const theme = createMuiTheme({
  components: {
    MuiButton: {
      styleOverrides: {
        root: () => ({
          fontSize: "1rem"
        })
      },
      variants: [
        {
          props: { variant: "text" },
          style: () => ({
            textTransform: "none"
          })
        }
      ]
    }
  }
});

export default function GlobalThemeOverride() {
  return (
    <ThemeProvider theme={theme}>
      <Button>font-size: 1rem</Button>
    </ThemeProvider>
  );
}

[oliviertassinari]

I'm not aware we have an open issue about it, I would propose we open one.

[mnajdova]

I'll look into this next week 👍

[mnajdova]

Should it be a function of the theme? Not sure if props makes sense

[oliviertassinari]

I think that it depends on what we want to support for the API?

I would personally use the props & styleProps from the styleOverrides key. As for the variants key, unclear.

[mnajdova]

Ok let's start the discussion on an dedicated PR 👍