I'm not super happy with this. But, the RwLock has been moved to the
`BaseObjInst::attrs` member. Although this is not exactly how it appears
in code, it basically does this:
type Ptr<T> = Arc<RwLock<T>>;
struct BaseObjInst {
attr: HashMap<String, Ptr<dyn Obj>>,
// etc
}
becomes
type Ptr<T> = Arc<T>;
struct BaseObjInst {
attr: RwLock<HashMap<String, ObjP>>,
// etc
}
This makes things a lot more ergonomic (don't have to use try_read() and
try_write() everywhere), but it also eliminates compile-time errors that
would catch mutability errors. This is currently rearing its ugly head
when initializing the typesystem, since `Type` needs to hold a circular
reference itself (which it already shouldn't be doing since it's a
reference-counted pointer!). Currently, all tests are failing because of
this limitation.
There are a couple of ways around this limitation.
The first solution would be just copying all of the object
instantiation code into the `init_types` function and avoid calling
`some_base_type.instantiate()`. This would probably be literal
copy-pasting, or maybe an (ugly) macro, and probably a nightmare to
maintain long-term. I don't like this option, but it would make
everything "just work" with reference-counted pointers.
The second solution would be to write our own garbage collector, which
would allow for circular references and (hypothetically) mutably
updating these references. This is something that I am looking into,
because I really want a RefCell that you can pass around in a more
ergonomic way.
I think the fundamental error that I'm running into is trying to borrow
the same value multiple times mutably, which you *really* shouldn't be
doing. I believe I need to write better code and does the same thing.
The only unsolved problem is circular references. This is not a problem
right now because I'm not writing code that has circular references
besides the base typesystem (which is not a problem because they need to
live the entire lifetime of the program), but it will be a latent
problem until it gets fixed.
Signed-off-by: Alek Ratzloff <alekratz@gmail.com>
