enum check on compilation

[kobi7]

I would like to suggest a feature request:

when branching on an enum, I would like to get a warning if I omit in the 'on' cases one of the enum fields.
one warning for each field.
even if I have an 'else' case.

This is very useful when adding another field, it will let me know all the places in code that I should update.

((the current alternative is throwing a notsupported or notimplemented exception on the else case, which is then more easily discovered. or assert false in that position. however this is on runtime.))

[Charles]

I've thought about doing this before. I was planning on not throwing the error if there was an else. After all you wouldn't usually need the else if you had covered all the enums.

But I think we might also need a directive to disable this in specific cases.