Just about every time I set up a new `Context.Provider`, I end up accidentally specifying a `values` prop rather than `value`.  While it's a minor error, generally I build the container in which the provider resides and commit it to the code base before I ever use it.  It's only later when I go to use it that I realize I did it again.  Since the `Context.Provider` seems pretty much useless without a `value` prop specified, I'd love it if there was a prop error if it is missing... especially if another prop is defined on the `Context.Provider` instead.
}
     Disconnect from the old current.
     It will get deleted.
    current.alternate = null;
    oldWorkInProgress.alternate = null;
     Connect to the new tree.
    newWorkInProgress.index = oldWorkInProgress.index;
    newWorkInProgress.sibling = oldWorkInProgress.sibling;
    newWorkInProgress.return = oldWorkInProgress.return;
    newWorkInProgress.ref = oldWorkInProgress.ref;
     Replace the child/sibling pointers above it.
    if (oldWorkInProgress === returnFiber.child) {
      returnFiber.child = newWorkInProgress;
    } else {
      let prevSibling = returnFiber.child;
      if (prevSibling === null) {
        throw new Error('Expected parent to have a child.');
      }
      while (prevSibling.sibling !== oldWorkInProgress) {
        prevSibling = prevSibling.sibling;
        if (prevSibling === null) {
          throw new Error('Expected to find the previous sibling.');
        }
      }
      prevSibling.sibling = newWorkInProgress;
    }
    
    
    const last = returnFiber.lastEffect;
    if (last !== null) {