Boxy

Or alternatively make `SemiSafeCell` not have a lifetime and just be `World | UnsafeCell` :thinking:

`With` have reason to exist in the data part i.e. `Option`

if we do this the "correct" impl is definitely `trait FilterWorldQuery: WorldQuery {}` not an entirely duplicated trait hierarchy. Though im not convinced we really _want_ to do this as...

`Query` is just as clear as `Query` to me if we understand filters as just being "the same" as the data generic except the data doesnt get returned

I think all the unsoundness to do with `!Send` stuff would just disappear if we made `World: !Send` hold like it ought to. I don't know whether its worth blocking...

Unlike `!Send` though, resources can _also_ be `!Sync` which makes the `resource.rs` methods that let you go `&self -> Ptr

I think it would be fine to make it all `pub(crate)` since we ought to be covering all the require functionality as `World` methods anyway :thinking: doesnt really change that...

Why were so many `#[inline]` changed to `#[inline(always)]` did you benchmark this and it improved stuff?

We should be moving in the opposite direction here, removing `EntityRef::get_unchecked_mut` not adding a `_by_id` variant

`&World` means shared access to components, we may use `&World` for interior mutability in places but this is a terrible idea as we also use `&World` to actually mean "shared...