Props Composition?

PropsComposition.js.flow

/* @flow */

type ButtonProps = {
  onClick: () => void,
  type: 'button' | 'reset' | 'submit',
  design: 'primary' | 'secondary' | 'page' | 'tooltipInfo' | 'tooltipDocs',
  onFocus: () => void,
  onmouseover: () => void,
  onmouseout: () => void,
  className:string,
  children: Array<HTMLElement>,
}

type IconProps = {
  glyph:string,
  className?: string,
  title?: string,
  width?: string,
  height?: string,
};

const IconButtonProps = Object.assign(ButtonProps, IconProps)