message: Remove propTypes from stylefn type
diff: import {themeGet} from '@styled-system/theme-get'
  -import React from 'react'
  import * as styledSystem from 'styled-system'
  import theme from './theme'
  -interface StyleFn extends styledSystem.styleFn {
  - propTypes?: React.WeakValidationMap<any>
  -}
  -
  const {get: getKey, compose, system} = styledSystem
  export const get = (key: string) => themeGet(key, getKey(theme, key))
  // Common props
  -export const COMMON: StyleFn = compose(styledSystem.space, styledSystem.color, styledSystem.display)
  +export const COMMON = compose(styledSystem.space, styledSystem.color, styledSystem.display)
  export interface SystemCommonProps
  extends styledSystem.ColorProps,
  @@ -29,7 +24,7 @@ const whiteSpace = system({
  }
  })
  -export const TYPOGRAPHY: StyleFn = compose(styledSystem.typography, whiteSpace)
  +export const TYPOGRAPHY = compose(styledSystem.typography, whiteSpace)
  export interface SystemTypographyProps extends styledSystem.TypographyProps {
  whiteSpace?: 'normal' | 'nowrap' | 'pre' | 'pre-wrap' | 'pre-line'
  @@ -37,30 +32,30 @@ export interface SystemTypographyProps extends styledSystem.TypographyProps {
  // Border props
  -export const BORDER: StyleFn = compose(styledSystem.border, styledSystem.shadow)
  +export const BORDER = compose(styledSystem.border, styledSystem.shadow)
  export interface SystemBorderProps extends styledSystem.BorderProps, styledSystem.ShadowProps {}
  // Layout props
  -export const LAYOUT: StyleFn = styledSystem.layout
  +export const LAYOUT = styledSystem.layout
  export type SystemLayoutProps = styledSystem.LayoutProps
  // Position props
  -export const POSITION: StyleFn = styledSystem.position
  +export const POSITION = styledSystem.position
  export type SystemPositionProps = styledSystem.PositionProps
  // Flex props
  -export const FLEX: StyleFn = styledSystem.flexbox
  +export const FLEX = styledSystem.flexbox
  export type SystemFlexProps = styledSystem.FlexboxProps
  // Grid props
  -export const GRID: StyleFn = styledSystem.grid
  +export const GRID = styledSystem.grid
  export type SystemGridProps = styledSystem.GridProps
  