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BennoLossinBennoLossin
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Merge pull request #75 from Rust-for-Linux/dev/pin-projections
add pin projections to `#[pin_data]`
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‎CHANGELOG.md‎

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@@ -7,6 +7,10 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
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## [Unreleased]
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### Changed
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- `#[pin_data]` now generates a `*Projection` struct similar to the `pin-project` crate.
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## [0.0.10] - 2025-08-19
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### Added

‎src/lib.rs‎

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@@ -994,7 +994,7 @@ macro_rules! try_init {
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/// }
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///
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/// impl<T> Foo<T> {
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/// fn project(self: Pin<&mut Self>) -> Pin<&mut T> {
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/// fn project_this(self: Pin<&mut Self>) -> Pin<&mut T> {
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/// assert_pinned!(Foo<T>, elem, T, inline);
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///
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/// // SAFETY: The field is structurally pinned.

‎src/macros.rs‎

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@@ -831,6 +831,17 @@ macro_rules! __pin_data {
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$($fields)*
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}
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$crate::__pin_data!(make_pin_projections:
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@vis($vis),
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@name($name),
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@impl_generics($($impl_generics)*),
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@ty_generics($($ty_generics)*),
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@decl_generics($($decl_generics)*),
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@where($($whr)*),
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@pinned($($pinned)*),
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@not_pinned($($not_pinned)*),
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);
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// We put the rest into this const item, because it then will not be accessible to anything
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// outside.
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const _: () = {
@@ -980,6 +991,56 @@ macro_rules! __pin_data {
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stringify!($($rest)*),
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);
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};
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(make_pin_projections:
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@vis($vis:vis),
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@name($name:ident),
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@impl_generics($($impl_generics:tt)*),
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@ty_generics($($ty_generics:tt)*),
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@decl_generics($($decl_generics:tt)*),
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@where($($whr:tt)*),
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@pinned($($(#[$($p_attr:tt)*])* $pvis:vis $p_field:ident : $p_type:ty),* $(,)?),
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@not_pinned($($(#[$($attr:tt)*])* $fvis:vis $field:ident : $type:ty),* $(,)?),
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) => {
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$crate::macros::paste! {
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#[doc(hidden)]
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$vis struct [< $name Projection >] <'__pin, $($decl_generics)*> {
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$($(#[$($p_attr)*])* $pvis $p_field : ::core::pin::Pin<&'__pin mut $p_type>,)*
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$($(#[$($attr)*])* $fvis $field : &'__pin mut $type,)*
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___pin_phantom_data: ::core::marker::PhantomData<&'__pin mut ()>,
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}
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impl<$($impl_generics)*> $name<$($ty_generics)*>
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where $($whr)*
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{
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/// Pin-projects all fields of `Self`.
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///
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/// These fields are structurally pinned:
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$(#[doc = ::core::concat!(" - `", ::core::stringify!($p_field), "`")])*
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///
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/// These fields are **not** structurally pinned:
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$(#[doc = ::core::concat!(" - `", ::core::stringify!($field), "`")])*
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#[inline]
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$vis fn project<'__pin>(
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self: ::core::pin::Pin<&'__pin mut Self>,
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) -> [< $name Projection >] <'__pin, $($ty_generics)*> {
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// SAFETY: we only give access to `&mut` for fields not structurally pinned.
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let this = unsafe { ::core::pin::Pin::get_unchecked_mut(self) };
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[< $name Projection >] {
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$(
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// SAFETY: `$p_field` is structurally pinned.
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$(#[$($p_attr)*])*
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$p_field : unsafe { ::core::pin::Pin::new_unchecked(&mut this.$p_field) },
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)*
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$(
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$(#[$($attr)*])*
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$field : &mut this.$field,
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)*
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___pin_phantom_data: ::core::marker::PhantomData,
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}
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}
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}
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}
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};
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(make_pin_data:
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@pin_data($pin_data:ident),
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@impl_generics($($impl_generics:tt)*),

‎tests/ui/compile-fail/init/wrong_generics2.stderr‎

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@@ -12,7 +12,7 @@ help: you might have forgotten to add the struct literal inside the block
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--> src/macros.rs
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|
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~ ::core::ptr::write($slot, $t { SomeStruct {
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|9 $($acc)*
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|0 $($acc)*
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~ } });
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|
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‎tests/ui/compile-fail/pin_data/twice.stderr‎

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@@ -1,3 +1,15 @@
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error[E0428]: the name `FooProjection` is defined multiple times
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--> tests/ui/compile-fail/pin_data/twice.rs:3:1
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|
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3 | #[pin_data]
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| ^^^^^^^^^^^
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| |
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| `FooProjection` redefined here
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| previous definition of the type `FooProjection` here
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|
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= note: `FooProjection` must be defined only once in the type namespace of this module
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= note: this error originates in the macro `$crate::__pin_data` which comes from the expansion of the attribute macro `pin_data` (in Nightly builds, run with -Z macro-backtrace for more info)
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error[E0119]: conflicting implementations of trait `HasPinData` for type `Foo`
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--> tests/ui/compile-fail/pin_data/twice.rs:3:1
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|
@@ -19,3 +31,24 @@ error[E0119]: conflicting implementations of trait `Unpin` for type `Foo`
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| conflicting implementation for `Foo`
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|
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= note: this error originates in the macro `$crate::__pin_data` which comes from the expansion of the attribute macro `pin_data` (in Nightly builds, run with -Z macro-backtrace for more info)
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error[E0592]: duplicate definitions with name `project`
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--> tests/ui/compile-fail/pin_data/twice.rs:3:1
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|
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3 | #[pin_data]
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| ^^^^^^^^^^^
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| |
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| duplicate definitions for `project`
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| other definition for `project`
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|
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= note: this error originates in the macro `$crate::__pin_data` which comes from the expansion of the attribute macro `pin_data` (in Nightly builds, run with -Z macro-backtrace for more info)
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error[E0308]: mismatched types
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--> tests/ui/compile-fail/pin_data/twice.rs:3:1
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|
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3 | #[pin_data]
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| ^^^^^^^^^^^ expected `&mut usize`, found `Pin<&mut usize>`
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|
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= note: expected mutable reference `&mut usize`
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found struct `Pin<&mut usize>`
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= note: this error originates in the macro `$crate::__pin_data` which comes from the expansion of the attribute macro `pin_data` (in Nightly builds, run with -Z macro-backtrace for more info)

‎tests/ui/expand/many_generics.expanded.rs‎

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@@ -12,6 +12,44 @@ where
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r: &'b mut [&'a mut T; SIZE],
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_pin: PhantomPinned,
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}
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#[doc(hidden)]
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struct FooProjection<
17+
'__pin,
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'a,
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'b: 'a,
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T: Bar<'b> + ?Sized + 'a,
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const SIZE: usize = 0,
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> {
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_pin: ::core::pin::Pin<&'__pin mut PhantomPinned>,
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array: &'__pin mut [u8; 1024 * 1024],
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r: &'__pin mut &'b mut [&'a mut T; SIZE],
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___pin_phantom_data: ::core::marker::PhantomData<&'__pin mut ()>,
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}
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impl<'a, 'b: 'a, T: Bar<'b> + ?Sized + 'a, const SIZE: usize> Foo<'a, 'b, T, SIZE>
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where
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T: Bar<'a, 1>,
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{
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/// Pin-projects all fields of `Self`.
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///
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/// These fields are structurally pinned:
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/// - `_pin`
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///
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/// These fields are **not** structurally pinned:
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/// - `array`
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/// - `r`
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#[inline]
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fn project<'__pin>(
42+
self: ::core::pin::Pin<&'__pin mut Self>,
43+
) -> FooProjection<'__pin, 'a, 'b, T, SIZE> {
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let this = unsafe { ::core::pin::Pin::get_unchecked_mut(self) };
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FooProjection {
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_pin: unsafe { ::core::pin::Pin::new_unchecked(&mut this._pin) },
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array: &mut this.array,
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r: &mut this.r,
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___pin_phantom_data: ::core::marker::PhantomData,
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}
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}
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}
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const _: () = {
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struct __ThePinData<'a, 'b: 'a, T: Bar<'b> + ?Sized + 'a, const SIZE: usize>
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where

‎tests/ui/expand/pin-data.expanded.rs‎

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@@ -4,6 +4,32 @@ struct Foo {
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array: [u8; 1024 * 1024],
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_pin: PhantomPinned,
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}
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#[doc(hidden)]
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struct FooProjection<'__pin> {
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_pin: ::core::pin::Pin<&'__pin mut PhantomPinned>,
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array: &'__pin mut [u8; 1024 * 1024],
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___pin_phantom_data: ::core::marker::PhantomData<&'__pin mut ()>,
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}
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impl Foo {
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/// Pin-projects all fields of `Self`.
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///
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/// These fields are structurally pinned:
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/// - `_pin`
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///
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/// These fields are **not** structurally pinned:
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/// - `array`
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#[inline]
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fn project<'__pin>(
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self: ::core::pin::Pin<&'__pin mut Self>,
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) -> FooProjection<'__pin> {
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let this = unsafe { ::core::pin::Pin::get_unchecked_mut(self) };
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FooProjection {
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_pin: unsafe { ::core::pin::Pin::new_unchecked(&mut this._pin) },
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array: &mut this.array,
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___pin_phantom_data: ::core::marker::PhantomData,
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}
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}
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}
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const _: () = {
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struct __ThePinData {
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__phantom: ::core::marker::PhantomData<fn(Foo) -> Foo>,

‎tests/ui/expand/pinned_drop.expanded.rs‎

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@@ -4,6 +4,32 @@ struct Foo {
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array: [u8; 1024 * 1024],
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_pin: PhantomPinned,
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}
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#[doc(hidden)]
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struct FooProjection<'__pin> {
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_pin: ::core::pin::Pin<&'__pin mut PhantomPinned>,
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array: &'__pin mut [u8; 1024 * 1024],
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___pin_phantom_data: ::core::marker::PhantomData<&'__pin mut ()>,
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}
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impl Foo {
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/// Pin-projects all fields of `Self`.
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///
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/// These fields are structurally pinned:
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/// - `_pin`
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///
19+
/// These fields are **not** structurally pinned:
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/// - `array`
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#[inline]
22+
fn project<'__pin>(
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self: ::core::pin::Pin<&'__pin mut Self>,
24+
) -> FooProjection<'__pin> {
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let this = unsafe { ::core::pin::Pin::get_unchecked_mut(self) };
26+
FooProjection {
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_pin: unsafe { ::core::pin::Pin::new_unchecked(&mut this._pin) },
28+
array: &mut this.array,
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___pin_phantom_data: ::core::marker::PhantomData,
30+
}
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}
32+
}
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const _: () = {
834
struct __ThePinData {
935
__phantom: ::core::marker::PhantomData<fn(Foo) -> Foo>,

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