EDIT: Turns out this syntax is not deprecated, it just needs to be fixed. 😃

When using this deprecated directive syntax:

Vue.directive('my-directive', function (value) {
  // this function will be used as update()
})

The errors thrown are:

vue.js:2168 [Vue warn]: Error during component render (found in root instance)
vue.js:3479 Uncaught TypeError: Bind must be called on a function

These are pretty vague, so wasn’t sure if we wanted to throw a better warning, similar to when users don’t have a root element in their template for example. Maybe something like:

[Vue warn]: Directive definition must be an object (Function definition is deprecated)