- interfaces can't directly contain instance initializers/constructors,
instance/local variables, or inner classes (maybe)
In order to have inner classes in an interface, we'd have to have a non-static
modifier, since nested classes in interfaces are allowed now and are implicitly
static.
Yep. But letting syntax drive this decision doesn't seem very much in the spirit of "anything
can be nested in anything", so maybe new syntax is worth it to iron out this wrinkle? Or
not—maybe "no new syntax" is where we draw the line.
It's not just syntax; it's not clear to me whether inner classes of
interfaces make enough sense / have enough applicability to warrant such
a change. My thinking was to smooth out the gratuitous restrictions
within the model we have, and clean up the language in the spec, and
then think about whether there's more to do.
- annotation types can't directly contain things prohibited in interfaces, or
instance/local methods (maybe)
- currently annos cannot have fields, default methods, or static methods --
this still seems a reasonable restriction.
Why? I mean, I don't really care all that much, but if we're removing ad hoc
restrictions, this one (no methods) certainly seems ad hoc. We don't even need
new syntax.
Because annotations are supposed to be pure metadata. These things all
pull state and behavior into something that is supposed to be pure
metadata. I mean, sure, I can imagine a world that blurs the
distinction between annotations and interfaces, but I'm not seeing these
restrictions as _gratuitous_; they were made deliberately.
