Allow class methods to have type parameters (this is a change from the
original classes proposal).
Add test cases for classes with type parameters, and classes with methods
that have their own type parameters.
All field or method references within a class must begin with "self." now.
A bare reference to a field or method in the same class will no longer
typecheck.
Allow writing self.f() within a class that has a method f. In a future
commit, this syntax will be required. For now, you can write either
self.f() or f().
I added a "privacy" field to all methods (whether class methods or not),
which allowed me to refactor the AST somewhat (getting rid of the
class_item type; now there's just class_member).
Allow writing self.f within a class that has a field f. Currently,
the compiler accepts either self.f or f. In a future commit I'll
require writing self.f and not f.
Not sure whether self.f() works if f is a method (making sure that
works next).
1. Enforce mutability declarations on class fields. Don't allow any
mutation of class fields not declared as mutable (except inside the
constructor).
2. Handle classes correctly in shape (treat classes like records).
The code is somewhat invasive, but it seems hard to do this in a
clean way, since the design itself involves a bunch of 'action
at a distance'.
Issue #1819
This was resulting in a different error message depending on whether
the private method you were trying to call was in the same crate
or a different one.
This change uses the same code for handling the "self" reference for
classes as is already used for impls/ifaces. This allows removing the
extra maybe_self_id argument (which was just for classes) to trans_closure
that I added before. I also rewrote the translation for class ctors so
that it doesn't generate new AST nodes (instead translating directly).
Also changed visit so that it visits class ctors correctly with visit_fn,
and changed typestate to not do return-checking when visiting a class ctor.
