const question/suggestion

[Sean Kelly]

Craig Black wrote:
> OK, I think I'm starting to grasp the subtle differences between const, 
> final, and invariant.  It seems to me that to have three keywords is 
> unnecessary.  Perhaps const and final could be merged into one?

Funny, I was going to say that about 'final' and 'invariant'.  So far as 
I can tell, the only difference between them from a user perspective is 
that 'invariant' is transitive while 'final' is not.  The ROMability of 
'invariant' is a compiler issue and is meaningless to the user.

> From my understanding, the only difference between const and final is that 
> local final fields can be initialized in a constructor, right?  Couldn't 
> that just be the default behavior of a local const field?  Then we could get 
> rid of final and have only two keywords.  Or am I missing something?  IMO, 
> two keywords is way less confusing than three.

That was my thought as well.

> Another question.  Since invariant data should always be invariant, does it 
> make sense to be able to cast non-invariant data to invariant?  The compiler 
> will think that it is invariant when it isn't.

This is probably just a matter of not making special cases for the 
compiler.  Casts are always allowed, even those that don't make sense.


Sean