fix: unsound cache upcast

[TroyKomodo]

Proposed changes

Removes the unsafe code around cache upcasting by introducing traited functions as_ref and as_mut on the AutoImplCacheRef trait. Also no longer requires the unsafe attribute.

Types of changes

What types of changes does your code introduce to Scuffle?
Put an x in the boxes that apply

• Bugfix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation Update (if none of the other choices apply)

Checklist

Put an x in the boxes that apply. You can also fill these out after creating the PR. If you're unsure about any of them, don't hesitate to ask. We're here to help! This is simply a reminder of what we are going to look for before merging your code.

• I have read the CONTRIBUTING doc
• Lint and unit tests pass locally with my changes
• I have added tests that prove my fix is effective or that my feature works
• I have added necessary documentation (if appropriate)
• Any dependent changes have been merged and published in downstream modules

Further comments

If this is a relatively large or complex change, you may want to start the discussion by explaining why you chose the solution you did, what alternatives you considered, etc.

[TroyKomodo]

There was actually nothing wrong with the way we used this. The issue would have been

struct CImpl {
   cache: Mutex<i32>
}

impl Cache {
  fn clear(&mut self) {
      *self.cache.get_mut() = 0;
  }
   ...
}

If the caller implemented the unsafe trait incorrectly it would be UB; now you might say well that is the point of the unsafe part. and you would be right, but i might as well catch it before they fuck up.

[lennartkloock]

My review is pretty useless here because I never wrote any unsafe and don't really know what's going on here. I don't even understand what this was for in the first place.

lgtm

[TroyKomodo]

My review is pretty useless here because I never wrote any unsafe and don't really know what's going on here. I don't even understand what this was for in the first place.

lgtm

It was so that we can allow for a cache to be a reference, rather than having an owned value. An example of this might be

let cache = SharedCache::new()

loader.load("key", &cache);
loader.load("key", &cache);

Rather than

let cache = Arc::new(SharedCache::new())

loader.load("key", cache.clone());
loader.load("key", cache.clone());

[lennartkloock]

It was so that we can allow for a cache to be a reference, rather than having an owned value. An example of this might be

I see.

Always good to remove unsafe code.