Following Python and Java's lead. Even TypeScript and ES.next, and (modulo a slight difference in syntax) C#.

Not sure I can fully motivate why I want to make this change, but (a) it feels a little bit more robust in some way, and (b) it's becoming clear that we can have use for traits on a number of things besides subs/macros:

• Classes
• Class properties

An example of the former: @Abstract; instead of making it a keyword. An example of the latter: @Readonly. Maybe @Lazy too.