message: filter out duplicate system props
diff: @@ -31,7 +31,8 @@ export const POSITION = [
  ]
  export function getSystemProps(props) {
  - return props.map(prop => {
  + const unique = props.filter((p, i, a) => a.indexOf(p) === i)
  + return unique.map(prop => {
  if (typeof system[prop] === 'function') {
  return system[prop]
  } else if (typeof prop === 'function') {
  