didn't generate classname

my css file:
```css
.date-picker {
&-header{
color: #000;
display: flex;
border: 1px solid #d9d9d9;
border-radius: 2px;
height: 32px;
align-items: center;
}
input {
border: none;
outline: none;
}
&::placeholder {
line-height: 1.5715;
font-size: 14px;
}
&-icon {
width: 14px;
height: 22px;
margin-right: 4px;
display: inline-block;
}
}
```
component
```tsx
import React, { SFC, useCallback } from 'react'
import moment from 'moment'
import { IHeaderProps } from './type'
import './style/header.less'

const MHeader: SFC = ({ setType, currentDate }) => {
const [startDate, endDate] = currentDate
const startText =
!startDate
? '请选择开始日期'
: moment(startDate!).format('YYYY-MM-DD') + ''
const endText =
!endDate
? '请选择结束日期'
: moment(endDate!).format('YYYY-MM-DD') + ''
const handleStartClick = useCallback(() => {
setType(0)
}, [setType])
const handleEndClick = useCallback(() => {
setType(1)
}, [setType])
return (

export default MHeader
```
generated dom like this
```html