Merge #90

90: Change the argument type of project method back to `self: Pin<&mut Self>` r=taiki-e a=taiki-e

Closes #89


Co-authored-by: Taiki Endo <te316e89@gmail.com>

README.md

@@ -48,7 +48,7 @@ struct Struct<T, U> {
 }
 
 impl<T, U> Struct<T, U> {
-    fn foo(mut self: Pin<&mut Self>) {
+    fn foo(self: Pin<&mut Self>) {
         let this = self.project();
         let _: Pin<&mut T> = this.pinned; // Pinned reference to the field
         let _: &mut U = this.unpinned; // Normal reference to the field

examples/enum-default-expanded.rs

@@ -30,18 +30,8 @@ enum __EnumProjection<'_pin, T, U> {
     Unpinned(&'_pin mut U),
 }
 
-impl<'_outer_pin, T, U> __EnumProjectionTrait<'_outer_pin, T, U>
-    for ::core::pin::Pin<&'_outer_pin mut Enum<T, U>>
-{
-    fn project<'_pin>(&'_pin mut self) -> __EnumProjection<'_pin, T, U> {
-        unsafe {
-            match self.as_mut().get_unchecked_mut() {
-                Enum::Pinned(_x0) => __EnumProjection::Pinned(::core::pin::Pin::new_unchecked(_x0)),
-                Enum::Unpinned(_x0) => __EnumProjection::Unpinned(_x0),
-            }
-        }
-    }
-    fn project_into(self) -> __EnumProjection<'_outer_pin, T, U> {
+impl<T, U> Enum<T, U> {
+    fn project<'_pin>(self: ::core::pin::Pin<&'_pin mut Self>) -> __EnumProjection<'_pin, T, U> {
         unsafe {
             match self.get_unchecked_mut() {
                 Enum::Pinned(_x0) => __EnumProjection::Pinned(::core::pin::Pin::new_unchecked(_x0)),
@@ -51,11 +41,6 @@ impl<'_outer_pin, T, U> __EnumProjectionTrait<'_outer_pin, T, U>
     }
 }
 
-trait __EnumProjectionTrait<'_outer_pin, T, U> {
-    fn project<'_pin>(&'_pin mut self) -> __EnumProjection<'_pin, T, U>;
-    fn project_into(self) -> __EnumProjection<'_outer_pin, T, U>;
-}
-
 // Automatically create the appropriate conditional `Unpin` implementation.
 //
 // See ./struct-default-expanded.rs and https://github.com/taiki-e/pin-project/pull/53.

examples/pinned_drop-expanded.rs

@@ -38,19 +38,8 @@ struct __FooProjection<'_pin, 'a, T> {
     field: ::core::pin::Pin<&'_pin mut T>,
 }
 
-impl<'_outer_pin, 'a, T> __FooProjectionTrait<'_outer_pin, 'a, T>
-    for ::core::pin::Pin<&'_outer_pin mut Foo<'a, T>>
-{
-    fn project<'_pin>(&'_pin mut self) -> __FooProjection<'_pin, 'a, T> {
-        unsafe {
-            let Foo { was_dropped, field } = self.as_mut().get_unchecked_mut();
-            __FooProjection {
-                was_dropped: was_dropped,
-                field: ::core::pin::Pin::new_unchecked(field),
-            }
-        }
-    }
-    fn project_into(self) -> __FooProjection<'_outer_pin, 'a, T> {
+impl<'a, T> Foo<'a, T> {
+    fn project<'_pin>(self: ::core::pin::Pin<&'_pin mut Self>) -> __FooProjection<'_pin, 'a, T> {
         unsafe {
             let Foo { was_dropped, field } = self.get_unchecked_mut();
             __FooProjection {
@@ -61,11 +50,6 @@ impl<'_outer_pin, 'a, T> __FooProjectionTrait<'_outer_pin, 'a, T>
     }
 }
 
-trait __FooProjectionTrait<'_outer_pin, 'a, T> {
-    fn project<'_pin>(&'_pin mut self) -> __FooProjection<'_pin, 'a, T>;
-    fn project_into(self) -> __FooProjection<'_outer_pin, 'a, T>;
-}
-
 #[allow(single_use_lifetimes)]
 impl<'a, T> ::core::ops::Drop for Foo<'a, T> {
     fn drop(&mut self) {
@@ -95,7 +79,7 @@ impl<'a, T> ::core::ops::Drop for Foo<'a, T> {
 impl<T> ::pin_project::__private::PinnedDrop for Foo<'_, T> {
     // Since calling it twice on the same object would be UB,
     // this method is unsafe.
-    unsafe fn drop(mut self: ::core::pin::Pin<&mut Self>) {
+    unsafe fn drop(self: Pin<&mut Self>) {
         **self.project().was_dropped = true;
     }
 }

examples/pinned_drop.rs

@@ -14,7 +14,7 @@ pub struct Foo<'a, T> {
 
 #[pinned_drop]
 impl<T> PinnedDrop for Foo<'_, T> {
-    fn drop(mut self: Pin<&mut Self>) {
+    fn drop(self: Pin<&mut Self>) {
         **self.project().was_dropped = true;
     }
 }

examples/struct-default-expanded.rs

@@ -31,19 +31,8 @@ struct __StructProjection<'_pin, T, U> {
     unpinned: &'_pin mut U,
 }
 
-impl<'_outer_pin, T, U> __StructProjectionTrait<'_outer_pin, T, U>
-    for ::core::pin::Pin<&'_outer_pin mut Struct<T, U>>
-{
-    fn project<'_pin>(&'_pin mut self) -> __StructProjection<'_pin, T, U> {
-        unsafe {
-            let Struct { pinned, unpinned } = self.as_mut().get_unchecked_mut();
-            __StructProjection {
-                pinned: ::core::pin::Pin::new_unchecked(pinned),
-                unpinned: unpinned,
-            }
-        }
-    }
-    fn project_into(self) -> __StructProjection<'_outer_pin, T, U> {
+impl<T, U> Struct<T, U> {
+    fn project<'_pin>(self: ::core::pin::Pin<&'_pin mut Self>) -> __StructProjection<'_pin, T, U> {
         unsafe {
             let Struct { pinned, unpinned } = self.get_unchecked_mut();
             __StructProjection {
@@ -54,11 +43,6 @@ impl<'_outer_pin, T, U> __StructProjectionTrait<'_outer_pin, T, U>
     }
 }
 
-trait __StructProjectionTrait<'_outer_pin, T, U> {
-    fn project<'_pin>(&'_pin mut self) -> __StructProjection<'_pin, T, U>;
-    fn project_into(self) -> __StructProjection<'_outer_pin, T, U>;
-}
-
 // Automatically create the appropriate conditional `Unpin` implementation.
 //
 // Basically this is equivalent to the following code:

examples/unsafe_unpin-expanded.rs

@@ -33,28 +33,15 @@ struct __FooProjection<'_pin, T, U> {
     unpinned: &'_pin mut U,
 }
 
-impl<'_outer_pin, T, U> __FooProjectionTrait<'_outer_pin, T, U>
-    for ::core::pin::Pin<&'_outer_pin mut Foo<T, U>>
-{
-    fn project<'_pin>(&'_pin mut self) -> __FooProjection<'_pin, T, U> {
-        unsafe {
-            let Foo { pinned, unpinned } = self.as_mut().get_unchecked_mut();
-            __FooProjection { pinned: ::core::pin::Pin::new_unchecked(pinned), unpinned: unpinned }
-        }
-    }
-    fn project_into(self) -> __FooProjection<'_outer_pin, T, U> {
+impl<T, U> Foo<T, U> {
+    fn project<'_pin>(self: ::core::pin::Pin<&'_pin mut Self>) -> __FooProjection<'_pin, T, U> {
         unsafe {
             let Foo { pinned, unpinned } = self.get_unchecked_mut();
             __FooProjection { pinned: ::core::pin::Pin::new_unchecked(pinned), unpinned: unpinned }
         }
     }
 }
 
-trait __FooProjectionTrait<'_outer_pin, T, U> {
-    fn project<'_pin>(&'_pin mut self) -> __FooProjection<'_pin, T, U>;
-    fn project_into(self) -> __FooProjection<'_outer_pin, T, U>;
-}
-
 unsafe impl<T: Unpin, U> UnsafeUnpin for Foo<T, U> {}
 
 impl<T, U> ::core::marker::Unpin for Foo<T, U> where

pin-project-internal/src/lib.rs

@@ -34,45 +34,20 @@ use syn::parse::Nothing;
 /// the field.
 /// - For the other fields, makes the unpinned reference to the field.
 ///
-/// The following methods are implemented on the original `#[pin_project]` type:
+/// The following method is implemented on the original `#[pin_project]` type:
 ///
 /// ```
 /// # #![feature(arbitrary_self_types)]
 /// # use std::pin::Pin;
 /// # type ProjectedType = ();
-/// # trait ProjectionTrait {
-/// fn project(self: &mut Pin<&mut Self>) -> ProjectedType;
-/// fn project_into(self: Pin<&mut Self>) -> ProjectedType;
+/// # trait Projection {
+/// fn project(self: Pin<&mut Self>) -> ProjectedType;
 /// # }
 /// ```
 ///
-/// The `project` method takes a mutable reference to a pinned
-/// type, and returns a projection struct. This is the method
-/// you'll usually want to use - since it takes a mutable reference,
-/// it can be called multiple times, and allows you to use
-/// the original Pin type later on (e.g. to call [`Pin::set`]).
-///
-/// The `project_into` type takes a pinned type by value (consuming it),
-/// and returns a projection struct. The difference between this and the `project`
-/// method lies in the lifetime. While the type returned by `project` only lives
-/// as long as the 'outer' mutable reference, the type returned by this method
-/// lives for as long as the original Pin. This can be useful when returning a pin
-/// projection from a method:
-///
-/// ```
-/// # use pin_project::pin_project;
-/// # use std::pin::Pin;
-/// # #[pin_project]
-/// # struct Struct<T> {
-/// #     #[pin]
-/// #     pinned: T,
-/// # }
-/// # impl<T> Struct<T> {
-/// fn get_pin_mut(self: Pin<&mut Self>) -> Pin<&mut T> {
-///     self.project_into().pinned
-/// }
-/// # }
-/// ```
+/// If you want to call the `project` method multiple times or later use the
+/// original Pin type, it needs to use [`.as_mut()`][`Pin::as_mut`] to avoid
+/// consuming the `Pin`.
 ///
 /// ## Safety
 ///
@@ -147,7 +122,7 @@ use syn::parse::Nothing;
 /// }
 ///
 /// impl<T, U> Foo<T, U> {
-///     fn baz(mut self: Pin<&mut Self>) {
+///     fn baz(self: Pin<&mut Self>) {
 ///         let this = self.project();
 ///         let _: Pin<&mut T> = this.future; // Pinned reference to the field
 ///         let _: &mut U = this.field; // Normal reference to the field
@@ -170,7 +145,7 @@ use syn::parse::Nothing;
 /// }
 ///
 /// impl<T, U> Foo<T, U> {
-///     fn baz(mut self: Pin<&mut Self>) {
+///     fn baz(self: Pin<&mut Self>) {
 ///         let this = self.project();
 ///         let _: Pin<&mut T> = this.future; // Pinned reference to the field
 ///         let _: &mut U = this.field; // Normal reference to the field
@@ -259,7 +234,7 @@ use syn::parse::Nothing;
 /// }
 ///
 /// impl<T, U> Foo<T, U> {
-///     fn baz(mut self: Pin<&mut Self>) {
+///     fn baz(self: Pin<&mut Self>) {
 ///         let this = self.project();
 ///         let _: Pin<&mut T> = this.future;
 ///         let _: &mut U = this.field;
@@ -277,7 +252,7 @@ use syn::parse::Nothing;
 /// struct Foo<T, U>(#[pin] T, U);
 ///
 /// impl<T, U> Foo<T, U> {
-///     fn baz(mut self: Pin<&mut Self>) {
+///     fn baz(self: Pin<&mut Self>) {
 ///         let this = self.project();
 ///         let _: Pin<&mut T> = this.0;
 ///         let _: &mut U = this.1;
@@ -316,7 +291,7 @@ use syn::parse::Nothing;
 /// # #[cfg(feature = "project_attr")]
 /// impl<A, B, C> Foo<A, B, C> {
 ///     #[project] // Nightly does not need a dummy attribute to the function.
-///     fn baz(mut self: Pin<&mut Self>) {
+///     fn baz(self: Pin<&mut Self>) {
 ///         #[project]
 ///         match self.project() {
 ///             Foo::Tuple(x, y) => {
@@ -422,7 +397,7 @@ pub fn pinned_drop(args: TokenStream, input: TokenStream) -> TokenStream {
 ///
 /// // impl for the original type
 /// impl<T, U> Foo<T, U> {
-///     fn bar(mut self: Pin<&mut Self>) {
+///     fn bar(self: Pin<&mut Self>) {
 ///         self.project().baz()
 ///     }
 /// }
@@ -459,7 +434,7 @@ pub fn pinned_drop(args: TokenStream, input: TokenStream) -> TokenStream {
 ///
 /// impl<T, U> Foo<T, U> {
 ///     #[project] // Nightly does not need a dummy attribute to the function.
-///     fn baz(mut self: Pin<&mut Self>) {
+///     fn baz(self: Pin<&mut Self>) {
 ///         #[project]
 ///         let Foo { future, field } = self.project();
 ///
@@ -489,7 +464,7 @@ pub fn pinned_drop(args: TokenStream, input: TokenStream) -> TokenStream {
 ///
 /// impl<A, B, C> Foo<A, B, C> {
 ///     #[project] // Nightly does not need a dummy attribute to the function.
-///     fn baz(mut self: Pin<&mut Self>) {
+///     fn baz(self: Pin<&mut Self>) {
 ///         #[project]
 ///         match self.project() {
 ///             Foo::Tuple(x, y) => {