Merge PinnedDrop and DropInner

Author: taiki-e

src/lib.rs

@@ -708,35 +708,17 @@ macro_rules! __pin_project_internal {
         )?
         {
             fn drop(&mut self) {
-                // Safety - we're in 'drop', so we know that 'self' will
-                // never move again.
-                let pinned_self = unsafe { $crate::__private::Pin::new_unchecked(self) };
-                // We call `pinned_drop` only once. Since `PinnedDrop::drop`
-                // is an unsafe method and a private API, it is never called again in safe
-                // code *unless the user uses a maliciously crafted macro*.
-                unsafe {
-                    $crate::__private::PinnedDrop::drop(pinned_self);
-                }
-            }
-        }
-        impl $(<
-            $( $lifetime $(: $lifetime_bound)? ),*
-            $( $generics
-                $(: $generics_bound)?
-                $(: ?$generics_unsized_bound)?
-                $(: $generics_lifetime_bound)?
-            ),*
-        >)? $crate::__private::PinnedDrop for $self_ty
-        $(where
-            $( $where_clause_ty
-                $(: $where_clause_bound)?
-                $(: ?$where_clause_unsized_bound)?
-                $(: $where_clause_lifetime_bound)?
-            ),*
-        )?
-        {
-            unsafe fn drop(self: $crate::__private::Pin<&mut Self>) {
-                trait __InnerDrop {
+                // Implementing `__DropInner::__drop_inner` is safe, but calling it is not safe.
+                // This is because destructors can be called multiple times in safe code and
+                // [double dropping is unsound](https://github.com/rust-lang/rust/pull/62360).
+                //
+                // `__drop_inner` is defined as a safe method, but this is fine since
+                // `__drop_inner` is not accessible by the users and we call `__drop_inner` only
+                // once.
+                //
+                // Users can implement [`Drop`] safely using `pin_project!` and can drop a
+                // type that implements `PinnedDrop` using the [`drop`] function safely.
+                trait __DropInner {
                     fn __drop_inner(self: $crate::__private::Pin<&mut Self>);
                 }
                 impl $(<
@@ -746,7 +728,7 @@ macro_rules! __pin_project_internal {
                         $(: ?$generics_unsized_bound)?
                         $(: $generics_lifetime_bound)?
                     ),*
-                >)? __InnerDrop for $self_ty
+                >)? __DropInner for $self_ty
                 $(where
                     $( $where_clause_ty
                         $(: $where_clause_bound)?
@@ -759,7 +741,13 @@ macro_rules! __pin_project_internal {
                         $($tt)*
                     }
                 }
-                __InnerDrop::__drop_inner(self);
+
+                // Safety - we're in 'drop', so we know that 'self' will
+                // never move again.
+                let pinned_self = unsafe { $crate::__private::Pin::new_unchecked(self) };
+                // We call `__drop_inner` only once. Since `__DropInner::__drop_inner`
+                // is not accessible by the users, it is never called again.
+                __DropInner::__drop_inner(pinned_self);
             }
         }
     };
@@ -871,24 +859,6 @@ pub mod __private {
         pin::Pin,
     };
 
-    // Implementing `PinnedDrop::drop` is safe, but calling it is not safe.
-    // This is because destructors can be called multiple times in safe code and
-    // [double dropping is unsound](https://github.com/rust-lang/rust/pull/62360).
-    //
-    // Ideally, it would be desirable to be able to forbid manual calls in
-    // the same way as [`Drop::drop`], but the library cannot do it. So, by using
-    // macros and replacing them with private traits, we prevent users from
-    // calling `PinnedDrop::drop`.
-    //
-    // Users can implement [`Drop`] safely using `#[pinned_drop]` and can drop a
-    // type that implements `PinnedDrop` using the [`drop`] function safely.
-    // **Do not call or implement this trait directly.**
-    #[doc(hidden)]
-    pub trait PinnedDrop {
-        #[doc(hidden)]
-        unsafe fn drop(self: Pin<&mut Self>);
-    }
-
     // This is an internal helper struct used by `pin_project!`.
     #[doc(hidden)]
     pub struct AlwaysUnpin<T: ?Sized>(PhantomData<T>);

tests/expand/tests/expand/pinned_drop-struct.expanded.rs

@@ -61,23 +61,16 @@ const _: () = {
     }
     impl<T, U> ::pin_project_lite::__private::Drop for Struct<T, U> {
         fn drop(&mut self) {
-            let pinned_self = unsafe { ::pin_project_lite::__private::Pin::new_unchecked(self) };
-            unsafe {
-                ::pin_project_lite::__private::PinnedDrop::drop(pinned_self);
-            }
-        }
-    }
-    impl<T, U> ::pin_project_lite::__private::PinnedDrop for Struct<T, U> {
-        unsafe fn drop(self: ::pin_project_lite::__private::Pin<&mut Self>) {
-            trait __InnerDrop {
+            trait __DropInner {
                 fn __drop_inner(self: ::pin_project_lite::__private::Pin<&mut Self>);
             }
-            impl<T, U> __InnerDrop for Struct<T, U> {
+            impl<T, U> __DropInner for Struct<T, U> {
                 fn __drop_inner(self: ::pin_project_lite::__private::Pin<&mut Self>) {
                     let _this = self;
                 }
             }
-            __InnerDrop::__drop_inner(self);
+            let pinned_self = unsafe { ::pin_project_lite::__private::Pin::new_unchecked(self) };
+            __DropInner::__drop_inner(pinned_self);
         }
     }
     #[deny(safe_packed_borrows)]