Function onlyChild

code/new-context-api/public/app.js:18649–18652

* Returns the first child in a collection of children and verifies that there * is only one child in the collection. * * See https://reactjs.org/docs/react-api.html#react.children.only * * The current implementation of this function assumes that a single child gets * passed without a wrapper,

(children)

 * structure.
 */
function onlyChild(children) {
  !isValidElement(children) ? invariant(false, 'React.Children.only expected to receive a single React element child.') : void 0;
  return children;
}

function createContext(defaultValue, calculateChangedBits) {
  if (calculateChangedBits === undefined) {