Why don't enums allow generics since Java 5? (was "Re: 2 questions about enums and the closed/withdrawn JEP 301")

[Brian Goetz]

My assumption is (a) that they were being co-developed and so they were 
focused on the compilation substrate they could count on, and (b) it's 
just impractically difficult to think ten steps ahead. Enums as they 
were done in Java 5 were already many steps ahead of enums in other 
languages of the day; enums in C were just aliases for ints, nothing 
more, whereas Java's enums were full blown objects with state and could 
implement interfaces, with constant-specific behavior.  When you're this 
many steps ahead of where the rest of the world is, it's hard to see 
more steps ahead; it's only after using them for a decade that the 
limitations start to chafe.

Similarly, the issues Maurizio raised about weaknesses in the generic 
type system were surely known at the time, and were probably dismissed 
as "glass .1% empty" (and reasonably so, at the time, given the scope 
and ambitiousness of the generics effort.)  Again, only decades later 
does our perspective on "no one really needs that" start to shift.

> Why were enums never given generics in the first place? I know they 
> came out in the same release, so theoretically, that was the best time 
> possible to bake this feature in and ensure it played well from the 
> beginning. Why didn't they?