NSAttributedString.Key in IOS

I am trying to define attibutes for Strings, with the following statement (IOS app)

var attributes = [NSAttributedString.Key: Any]() 
attributes[NSAttributedString.Key.foregroundColor] = newColor

I get a compiler error :

Type 'NSAttributedString.Key' (aka 'NSString') has no member 'foregroundColor'

even though the constant is defined in doc

So I change to

attributes[NSForegroundColorAttributeName] = newColor

Get another error:

Cannot subscript a value of type '[NSAttributedString.Key : Any]' (aka 'Dictionary<NSString, Any>') with an index of type 'String'

Which is bizarre again, as when I test (option-click in attribute name) the type of NSForegroundColorAttributeName, I get

static let foregroundColor: NSAttributedString.Key

I finally change to:

attributes[NSForegroundColorAttributeName as NSAttributedString.Key] = newColor

which works.

Am I missing something or is this a bit messy ?