On Thu, Jul 25, 2024 at 06:12:56PM +0000, Benno Lossin wrote: > On 24.07.24 19:44, Boqun Feng wrote: > > On Tue, Jul 23, 2024 at 11:14:29AM +0200, Alice Ryhl wrote: > >>> +/// However `&Self` represents a reference to the object, and the lifetime of the **reference** is > >>> +/// known at compile-time. E.g. the `Foo::as_ref()` above. > >>> +/// > >>> +/// ## `impl Drop` of an `impl AlwaysRefCounted` should not touch the refcount > >>> +/// > >>> +/// [`ARef`] descreases the refcount automatically (in [`ARef::drop`]) when it goes out of the > >>> +/// scope, therefore there's no need to `impl Drop` for the type of objects (e.g. `Foo`) to decrease > >>> +/// the refcount. > >>> pub struct ARef<T: AlwaysRefCounted> { > >>> ptr: NonNull<T>, > >>> _p: PhantomData<T>, > >>> -- > >>> 2.45.2 > >>> > >> > >> I think this is missing some basic information related to `&Self` -> > >> `ARef<Self>` conversions. We should explain that these conversions are > >> possible, and that you usually don't want `raw_ptr` -> `ARef<Self>` to > >> increment the refcount - instead provide a `raw_ptr` -> `&Self` and > >> convert the `&Self` to `ARef<Self>`. > >> > > > > I could be more explicit on this, but could there be a case where a `T` > > only wants to return `ARef<T>` as a public API? In other words, the > > author of `T` doesn't want to expose an `-> &T` function, therefore a > > `-> ARef<T>` function makes more sense? If all the users of `T` want to > > operate on an `ARef<T>` other than `&T`, I think it makes sense, right? > > You can always get a `&T` from `ARef<T>`, since it implements `Deref`. > Yeah, but this is unrelated. I was talking about that API providers can decide whether they want to only provide a `raw_ptr` -> `ARef<Self>` if they don't need to provide a `raw_ptr` -> `&Self`. > > Overall, I feel like we don't necessarily make a preference between > > `->&Self` and `->ARef<Self>` functions here, since it's up to the users' > > design? > > I would argue that there should be a clear preference for functions > returning `&Self` when possible (ie there is a parameter that the If "possible" also means there's going to be `raw_ptr` -> `&Self` function (as the same publicity level) anyway, then agreed. In other words, if the users only need the `raw_ptr` -> `ARef<Self>` functionality, we don't want to force people to provide a `raw_ptr` -> `&Self` just because, right? Regards, Boqun > lifetime can bind to). This is because then you get the two versions of > the function (non-incrementing and incrementing) for the price of one > function. > > --- > Cheers, > Benno >