If called with a function then it's considered to be the controller constructor function. Otherwise it's considered to be a string which is used to retrieve the controller constructor using the following steps:

• check if a controller with given name is registered via $controllerProvider
• check if evaluating the string on the current scope returns a constructor

• if $controllerProvider#allowGlobals, check window[constructor] on the global window object (not recommended)

  The string can use the controller as property syntax, where the controller instance is published as the specified property on the scope; the scope must be injected into locals param for this to work correctly.

Injection locals for Controller.