makeStyles: Does not correctly handle sequence expressions

[khmakoto]

This problem affected #20918 and #20657:

ERROR in /mnt/vss/_work/1/s/packages/react-switch/src/components/Switch/useSwitchStyles.ts
Module build failed (from /mnt/vss/_work/1/s/packages/make-styles-webpack-loader/lib/index.js):
SyntaxError: /mnt/vss/_work/1/s/packages/react-switch/src/components/Switch/useSwitchStyles.ts: We met an unhandled case, this is a bug, please include a stacktrace and report it at https://github.com/microsoft/fluentui
  56 |     verticalAlign: 'bottom'
  57 |   },
> 58 |   unchecked: (_a = {}, _a[":hover ." + thumbClassName] = {
     |   ^
  59 |     ':before': {
  60 |       backgroundColor: react_theme_1.tokens.colorNeutralStrokeAccessibleHover
  61 |     }
    at File.buildCodeFrameError (/mnt/vss/_work/1/s/node_modules/@babel/core/lib/transformation/file/file.js:244:12)
    at NodePath.buildCodeFrameError (/mnt/vss/_work/1/s/node_modules/@babel/traverse/lib/path/index.js:133:21)

@layershifter and I traced it down to a minimal repro:

import { makeStyles, MakeStylesStyle } from '@fluentui/react-make-styles';

const switchClassName = 'fui-Switch';
let _a: Record<string, MakeStylesStyle>;

export const useStyles = makeStyles({
  root:
    ((_a = {}),
    (_a[':hover .' + switchClassName] = {
      ':before': {
        backgroundColor: 'red',
      },
    }),
    _a),
});