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+// SPDX-License-Identifier: Apache-2.0 OR MIT
+
+//! This module provides the macros that actually implement the proc-macros `pin_data` and
+//! `pinned_drop`.
+//!
+//! These macros should never be called directly, since they expect their input to be
+//! in a certain format which is internal. Use the proc-macros instead.
+//!
+//! This architecture has been chosen because the kernel does not yet have access to `syn` which
+//! would make matters a lot easier for implementing these as proc-macros.
+//!
+//! # Macro expansion example
+//!
+//! This section is intended for readers trying to understand the macros in this module and the
+//! `pin_init!` macros from `init.rs`.
+//!
+//! We will look at the following example:
+//!
+//! ```rust
+//! # use kernel::init::*;
+//! #[pin_data]
+//! #[repr(C)]
+//! struct Bar<T> {
+//! #[pin]
+//! t: T,
+//! pub x: usize,
+//! }
+//!
+//! impl<T> Bar<T> {
+//! fn new(t: T) -> impl PinInit<Self> {
+//! pin_init!(Self { t, x: 0 })
+//! }
+//! }
+//! ```
+//!
+//! This example includes the most common and important features of the pin-init API.
+//!
+//! Below you can find individual section about the different macro invocations. Here are some
+//! general things we need to take into account when designing macros:
+//! - use global paths, similarly to file paths, these start with the separator: `::core::panic!()`
+//! this ensures that the correct item is used, since users could define their own `mod core {}`
+//! and then their own `panic!` inside to execute arbitrary code inside of our macro.
+//! - macro `unsafe` hygiene: we need to ensure that we do not expand arbitrary, user-supplied
+//! expressions inside of an `unsafe` block in the macro, because this would allow users to do
+//! `unsafe` operations without an associated `unsafe` block.
+//!
+//! ## `#[pin_data]` on `Bar`
+//!
+//! This macro is used to specify which fields are structurally pinned and which fields are not. It
+//! is placed on the struct definition and allows `#[pin]` to be placed on the fields.
+//!
+//! Here is the definition of `Bar` from our example:
+//!
+//! ```rust
+//! # use kernel::init::*;
+//! #[pin_data]
+//! #[repr(C)]
+//! struct Bar<T> {
+//! t: T,
+//! pub x: usize,
+//! }
+//! ```
+//!
+//! This expands to the following code:
+//!
+//! ```rust
+//! // Firstly the normal definition of the struct, attributes are preserved:
+//! #[repr(C)]
+//! struct Bar<T> {
+//! t: T,
+//! pub x: usize,
+//! }
+//! // Then an anonymous constant is defined, this is because we do not want any code to access the
+//! // types that we define inside:
+//! const _: () = {
+//! // We define the pin-data carrying struct, it is a ZST and needs to have the same generics,
+//! // since we need to implement access functions for each field and thus need to know its
+//! // type.
+//! struct __ThePinData<T> {
+//! __phantom: ::core::marker::PhantomData<fn(Bar<T>) -> Bar<T>>,
+//! }
+//! // We implement `Copy` for the pin-data struct, since all functions it defines will take
+//! // `self` by value.
+//! impl<T> ::core::clone::Clone for __ThePinData<T> {
+//! fn clone(&self) -> Self {
+//! *self
+//! }
+//! }
+//! impl<T> ::core::marker::Copy for __ThePinData<T> {}
+//! // For every field of `Bar`, the pin-data struct will define a function with the same name
+//! // and accessor (`pub` or `pub(crate)` etc.). This function will take a pointer to the
+//! // field (`slot`) and a `PinInit` or `Init` depending on the projection kind of the field
+//! // (if pinning is structural for the field, then `PinInit` otherwise `Init`).
+//! #[allow(dead_code)]
+//! impl<T> __ThePinData<T> {
+//! unsafe fn t<E>(
+//! self,
+//! slot: *mut T,
+//! init: impl ::kernel::init::Init<T, E>,
+//! ) -> ::core::result::Result<(), E> {
+//! unsafe { ::kernel::init::Init::__init(init, slot) }
+//! }
+//! pub unsafe fn x<E>(
+//! self,
+//! slot: *mut usize,
+//! init: impl ::kernel::init::Init<usize, E>,
+//! ) -> ::core::result::Result<(), E> {
+//! unsafe { ::kernel::init::Init::__init(init, slot) }
+//! }
+//! }
+//! // Implement the internal `HasPinData` trait that associates `Bar` with the pin-data struct
+//! // that we constructed beforehand.
+//! unsafe impl<T> ::kernel::init::__internal::HasPinData for Bar<T> {
+//! type PinData = __ThePinData<T>;
+//! unsafe fn __pin_data() -> Self::PinData {
+//! __ThePinData {
+//! __phantom: ::core::marker::PhantomData,
+//! }
+//! }
+//! }
+//! // Implement the internal `PinData` trait that marks the pin-data struct as a pin-data
+//! // struct. This is important to ensure that no user can implement a rouge `__pin_data`
+//! // function without using `unsafe`.
+//! unsafe impl<T> ::kernel::init::__internal::PinData for __ThePinData<T> {
+//! type Datee = Bar<T>;
+//! }
+//! // Now we only want to implement `Unpin` for `Bar` when every structurally pinned field is
+//! // `Unpin`. In other words, whether `Bar` is `Unpin` only depends on structurally pinned
+//! // fields (those marked with `#[pin]`). These fields will be listed in this struct, in our
+//! // case no such fields exist, hence this is almost empty. The two phantomdata fields exist
+//! // for two reasons:
+//! // - `__phantom`: every generic must be used, since we cannot really know which generics
+//! // are used, we declere all and then use everything here once.
+//! // - `__phantom_pin`: uses the `'__pin` lifetime and ensures that this struct is invariant
+//! // over it. The lifetime is needed to work around the limitation that trait bounds must
+//! // not be trivial, e.g. the user has a `#[pin] PhantomPinned` field -- this is
+//! // unconditionally `!Unpin` and results in an error. The lifetime tricks the compiler
+//! // into accepting these bounds regardless.
+//! #[allow(dead_code)]
+//! struct __Unpin<'__pin, T> {
+//! __phantom_pin: ::core::marker::PhantomData<fn(&'__pin ()) -> &'__pin ()>,
+//! __phantom: ::core::marker::PhantomData<fn(Bar<T>) -> Bar<T>>,
+//! }
+//! #[doc(hidden)]
+//! impl<'__pin, T>
+//! ::core::marker::Unpin for Bar<T> where __Unpin<'__pin, T>: ::core::marker::Unpin {}
+//! // Now we need to ensure that `Bar` does not implement `Drop`, since that would give users
+//! // access to `&mut self` inside of `drop` even if the struct was pinned. This could lead to
+//! // UB with only safe code, so we disallow this by giving a trait implementation error using
+//! // a direct impl and a blanket implementation.
+//! trait MustNotImplDrop {}
+//! // Normally `Drop` bounds do not have the correct semantics, but for this purpose they do
+//! // (normally people want to know if a type has any kind of drop glue at all, here we want
+//! // to know if it has any kind of custom drop glue, which is exactly what this bound does).
+//! #[allow(drop_bounds)]
+//! impl<T: ::core::ops::Drop> MustNotImplDrop for T {}
+//! impl<T> MustNotImplDrop for Bar<T> {}
+//! };
+//! ```
+//!
+//! ## `pin_init!` in `impl Bar`
+//!
+//! This macro creates an pin-initializer for the given struct. It requires that the struct is
+//! annotated by `#[pin_data]`.
+//!
+//! Here is the impl on `Bar` defining the new function:
+//!
+//! ```rust
+//! impl<T> Bar<T> {
+//! fn new(t: T) -> impl PinInit<Self> {
+//! pin_init!(Self { t, x: 0 })
+//! }
+//! }
+//! ```
+//!
+//! This expands to the following code:
+//!
+//! ```rust
+//! impl<T> Bar<T> {
+//! fn new(t: T) -> impl PinInit<Self> {
+//! {
+//! // We do not want to allow arbitrary returns, so we declare this type as the `Ok`
+//! // return type and shadow it later when we insert the arbitrary user code. That way
+//! // there will be no possibility of returning without `unsafe`.
+//! struct __InitOk;
+//! // Get the pin-data type from the initialized type.
+//! // - the function is unsafe, hence the unsafe block
+//! // - we `use` the `HasPinData` trait in the block, it is only available in that
+//! // scope.
+//! let data = unsafe {
+//! use ::kernel::init::__internal::HasPinData;
+//! Self::__pin_data()
+//! };
+//! // Use `data` to help with type inference, the closure supplied will have the type
+//! // `FnOnce(*mut Self) -> Result<__InitOk, Infallible>`.
+//! let init = ::kernel::init::__internal::PinData::make_closure::<
+//! _,
+//! __InitOk,
+//! ::core::convert::Infallible,
+//! >(data, move |slot| {
+//! {
+//! // Shadow the structure so it cannot be used to return early. If a user
+//! // tries to write `return Ok(__InitOk)`, then they get a type error, since
+//! // that will refer to this struct instead of the one defined above.
+//! struct __InitOk;
+//! // This is the expansion of `t,`, which is syntactic sugar for `t: t,`.
+//! unsafe { ::core::ptr::write(&raw mut (*slot).t, t) };
+//! // Since initialization could fail later (not in this case, since the error
+//! // type is `Infallible`) we will need to drop this field if it fails. This
+//! // `DropGuard` will drop the field when it gets dropped and has not yet
+//! // been forgotten. We make a reference to it, so users cannot `mem::forget`
+//! // it from the initializer, since the name is the same as the field.
+//! let t = &unsafe {
+//! ::kernel::init::__internal::DropGuard::new(&raw mut (*slot).t)
+//! };
+//! // Expansion of `x: 0,`:
+//! // Since this can be an arbitrary expression we cannot place it inside of
+//! // the `unsafe` block, so we bind it here.
+//! let x = 0;
+//! unsafe { ::core::ptr::write(&raw mut (*slot).x, x) };
+//! let x = &unsafe {
+//! ::kernel::init::__internal::DropGuard::new(&raw mut (*slot).x)
+//! };
+//!
+//! // Here we use the type checker to ensuer that every field has been
+//! // initialized exactly once, since this is `if false` it will never get
+//! // executed, but still type-checked.
+//! // Additionally we abuse `slot` to automatically infer the correct type for
+//! // the struct. This is also another check that every field is accessible
+//! // from this scope.
+//! #[allow(unreachable_code, clippy::diverging_sub_expression)]
+//! if false {
+//! unsafe {
+//! ::core::ptr::write(
+//! slot,
+//! Self {
+//! // We only care about typecheck finding every field here,
+//! // the expression does not matter, just conjure one using
+//! // `panic!()`:
+//! t: ::core::panic!(),
+//! x: ::core::panic!(),
+//! },
+//! );
+//! };
+//! }
+//! // Since initialization has successfully completed, we can now forget the
+//! // guards.
+//! unsafe { ::kernel::init::__internal::DropGuard::forget(t) };
+//! unsafe { ::kernel::init::__internal::DropGuard::forget(x) };
+//! }
+//! // We leave the scope above and gain access to the previously shadowed
+//! // `__InitOk` that we need to return.
+//! Ok(__InitOk)
+//! });
+//! // Change the return type of the closure.
+//! let init = move |slot| -> ::core::result::Result<(), ::core::convert::Infallible> {
+//! init(slot).map(|__InitOk| ())
+//! };
+//! // Construct the initializer.
+//! let init = unsafe {
+//! ::kernel::init::pin_init_from_closure::<_, ::core::convert::Infallible>(init)
+//! };
+//! init
+//! }
+//! }
+//! }
+//! ```
+
+/// This macro first parses the struct definition such that it separates pinned and not pinned
+/// fields. Afterwards it declares the struct and implement the `PinData` trait safely.
+#[doc(hidden)]
+#[macro_export]
+macro_rules! __pin_data {
+ // Proc-macro entry point, this is supplied by the proc-macro pre-parsing.
+ (parse_input:
+ @args($($pinned_drop:ident)?),
+ @sig(
+ $(#[$($struct_attr:tt)*])*
+ $vis:vis struct $name:ident
+ $(where $($whr:tt)*)?
+ ),
+ @impl_generics($($impl_generics:tt)*),
+ @ty_generics($($ty_generics:tt)*),
+ @body({ $($fields:tt)* }),
+ ) => {
+ // We now use token munching to iterate through all of the fields. While doing this we
+ // identify fields marked with `#[pin]`, these fields are the 'pinned fields'. The user
+ // wants these to be structurally pinned. The rest of the fields are the
+ // 'not pinned fields'. Additionally we collect all fields, since we need them in the right
+ // order to declare the struct.
+ //
+ // In this call we also put some explaining comments for the parameters.
+ $crate::__pin_data!(find_pinned_fields:
+ // Attributes on the struct itself, these will just be propagated to be put onto the
+ // struct definition.
+ @struct_attrs($(#[$($struct_attr)*])*),
+ // The visibility of the struct.
+ @vis($vis),
+ // The name of the struct.
+ @name($name),
+ // The 'impl generics', the generics that will need to be specified on the struct inside
+ // of an `impl<$ty_generics>` block.
+ @impl_generics($($impl_generics)*),
+ // The 'ty generics', the generics that will need to be specified on the impl blocks.
+ @ty_generics($($ty_generics)*),
+ // The where clause of any impl block and the declaration.
+ @where($($($whr)*)?),
+ // The remaining fields tokens that need to be processed.
+ // We add a `,` at the end to ensure correct parsing.
+ @fields_munch($($fields)* ,),
+ // The pinned fields.
+ @pinned(),
+ // The not pinned fields.
+ @not_pinned(),
+ // All fields.
+ @fields(),
+ // The accumulator containing all attributes already parsed.
+ @accum(),
+ // Contains `yes` or `` to indicate if `#[pin]` was found on the current field.
+ @is_pinned(),
+ // The proc-macro argument, this should be `PinnedDrop` or ``.
+ @pinned_drop($($pinned_drop)?),
+ );
+ };
+ (find_pinned_fields:
+ @struct_attrs($($struct_attrs:tt)*),
+ @vis($vis:vis),
+ @name($name:ident),
+ @impl_generics($($impl_generics:tt)*),
+ @ty_generics($($ty_generics:tt)*),
+ @where($($whr:tt)*),
+ // We found a PhantomPinned field, this should generally be pinned!
+ @fields_munch($field:ident : $($($(::)?core::)?marker::)?PhantomPinned, $($rest:tt)*),
+ @pinned($($pinned:tt)*),
+ @not_pinned($($not_pinned:tt)*),
+ @fields($($fields:tt)*),
+ @accum($($accum:tt)*),
+ // This field is not pinned.
+ @is_pinned(),
+ @pinned_drop($($pinned_drop:ident)?),
+ ) => {
+ ::core::compile_error!(concat!(
+ "The field `",
+ stringify!($field),
+ "` of type `PhantomPinned` only has an effect, if it has the `#[pin]` attribute.",
+ ));
+ $crate::__pin_data!(find_pinned_fields:
+ @struct_attrs($($struct_attrs)*),
+ @vis($vis),
+ @name($name),
+ @impl_generics($($impl_generics)*),
+ @ty_generics($($ty_generics)*),
+ @where($($whr)*),
+ @fields_munch($($rest)*),
+ @pinned($($pinned)* $($accum)* $field: ::core::marker::PhantomPinned,),
+ @not_pinned($($not_pinned)*),
+ @fields($($fields)* $($accum)* $field: ::core::marker::PhantomPinned,),
+ @accum(),
+ @is_pinned(),
+ @pinned_drop($($pinned_drop)?),
+ );
+ };
+ (find_pinned_fields:
+ @struct_attrs($($struct_attrs:tt)*),
+ @vis($vis:vis),
+ @name($name:ident),
+ @impl_generics($($impl_generics:tt)*),
+ @ty_generics($($ty_generics:tt)*),
+ @where($($whr:tt)*),
+ // We reached the field declaration.
+ @fields_munch($field:ident : $type:ty, $($rest:tt)*),
+ @pinned($($pinned:tt)*),
+ @not_pinned($($not_pinned:tt)*),
+ @fields($($fields:tt)*),
+ @accum($($accum:tt)*),
+ // This field is pinned.
+ @is_pinned(yes),
+ @pinned_drop($($pinned_drop:ident)?),
+ ) => {
+ $crate::__pin_data!(find_pinned_fields:
+ @struct_attrs($($struct_attrs)*),
+ @vis($vis),
+ @name($name),
+ @impl_generics($($impl_generics)*),
+ @ty_generics($($ty_generics)*),
+ @where($($whr)*),
+ @fields_munch($($rest)*),
+ @pinned($($pinned)* $($accum)* $field: $type,),
+ @not_pinned($($not_pinned)*),
+ @fields($($fields)* $($accum)* $field: $type,),
+ @accum(),
+ @is_pinned(),
+ @pinned_drop($($pinned_drop)?),
+ );
+ };
+ (find_pinned_fields:
+ @struct_attrs($($struct_attrs:tt)*),
+ @vis($vis:vis),
+ @name($name:ident),
+ @impl_generics($($impl_generics:tt)*),
+ @ty_generics($($ty_generics:tt)*),
+ @where($($whr:tt)*),
+ // We reached the field declaration.
+ @fields_munch($field:ident : $type:ty, $($rest:tt)*),
+ @pinned($($pinned:tt)*),
+ @not_pinned($($not_pinned:tt)*),
+ @fields($($fields:tt)*),
+ @accum($($accum:tt)*),
+ // This field is not pinned.
+ @is_pinned(),
+ @pinned_drop($($pinned_drop:ident)?),
+ ) => {
+ $crate::__pin_data!(find_pinned_fields:
+ @struct_attrs($($struct_attrs)*),
+ @vis($vis),
+ @name($name),
+ @impl_generics($($impl_generics)*),
+ @ty_generics($($ty_generics)*),
+ @where($($whr)*),
+ @fields_munch($($rest)*),
+ @pinned($($pinned)*),
+ @not_pinned($($not_pinned)* $($accum)* $field: $type,),
+ @fields($($fields)* $($accum)* $field: $type,),
+ @accum(),
+ @is_pinned(),
+ @pinned_drop($($pinned_drop)?),
+ );
+ };
+ (find_pinned_fields:
+ @struct_attrs($($struct_attrs:tt)*),
+ @vis($vis:vis),
+ @name($name:ident),
+ @impl_generics($($impl_generics:tt)*),
+ @ty_generics($($ty_generics:tt)*),
+ @where($($whr:tt)*),
+ // We found the `#[pin]` attr.
+ @fields_munch(#[pin] $($rest:tt)*),
+ @pinned($($pinned:tt)*),
+ @not_pinned($($not_pinned:tt)*),
+ @fields($($fields:tt)*),
+ @accum($($accum:tt)*),
+ @is_pinned($($is_pinned:ident)?),
+ @pinned_drop($($pinned_drop:ident)?),
+ ) => {
+ $crate::__pin_data!(find_pinned_fields:
+ @struct_attrs($($struct_attrs)*),
+ @vis($vis),
+ @name($name),
+ @impl_generics($($impl_generics)*),
+ @ty_generics($($ty_generics)*),
+ @where($($whr)*),
+ @fields_munch($($rest)*),
+ // We do not include `#[pin]` in the list of attributes, since it is not actually an
+ // attribute that is defined somewhere.
+ @pinned($($pinned)*),
+ @not_pinned($($not_pinned)*),
+ @fields($($fields)*),
+ @accum($($accum)*),
+ // Set this to `yes`.
+ @is_pinned(yes),
+ @pinned_drop($($pinned_drop)?),
+ );
+ };
+ (find_pinned_fields:
+ @struct_attrs($($struct_attrs:tt)*),
+ @vis($vis:vis),
+ @name($name:ident),
+ @impl_generics($($impl_generics:tt)*),
+ @ty_generics($($ty_generics:tt)*),
+ @where($($whr:tt)*),
+ // We reached the field declaration with visibility, for simplicity we only munch the
+ // visibility and put it into `$accum`.
+ @fields_munch($fvis:vis $field:ident $($rest:tt)*),
+ @pinned($($pinned:tt)*),
+ @not_pinned($($not_pinned:tt)*),
+ @fields($($fields:tt)*),
+ @accum($($accum:tt)*),
+ @is_pinned($($is_pinned:ident)?),
+ @pinned_drop($($pinned_drop:ident)?),
+ ) => {
+ $crate::__pin_data!(find_pinned_fields:
+ @struct_attrs($($struct_attrs)*),
+ @vis($vis),
+ @name($name),
+ @impl_generics($($impl_generics)*),
+ @ty_generics($($ty_generics)*),
+ @where($($whr)*),
+ @fields_munch($field $($rest)*),
+ @pinned($($pinned)*),
+ @not_pinned($($not_pinned)*),
+ @fields($($fields)*),
+ @accum($($accum)* $fvis),
+ @is_pinned($($is_pinned)?),
+ @pinned_drop($($pinned_drop)?),
+ );
+ };
+ (find_pinned_fields:
+ @struct_attrs($($struct_attrs:tt)*),
+ @vis($vis:vis),
+ @name($name:ident),
+ @impl_generics($($impl_generics:tt)*),
+ @ty_generics($($ty_generics:tt)*),
+ @where($($whr:tt)*),
+ // Some other attribute, just put it into `$accum`.
+ @fields_munch(#[$($attr:tt)*] $($rest:tt)*),
+ @pinned($($pinned:tt)*),
+ @not_pinned($($not_pinned:tt)*),
+ @fields($($fields:tt)*),
+ @accum($($accum:tt)*),
+ @is_pinned($($is_pinned:ident)?),
+ @pinned_drop($($pinned_drop:ident)?),
+ ) => {
+ $crate::__pin_data!(find_pinned_fields:
+ @struct_attrs($($struct_attrs)*),
+ @vis($vis),
+ @name($name),
+ @impl_generics($($impl_generics)*),
+ @ty_generics($($ty_generics)*),
+ @where($($whr)*),
+ @fields_munch($($rest)*),
+ @pinned($($pinned)*),
+ @not_pinned($($not_pinned)*),
+ @fields($($fields)*),
+ @accum($($accum)* #[$($attr)*]),
+ @is_pinned($($is_pinned)?),
+ @pinned_drop($($pinned_drop)?),
+ );
+ };
+ (find_pinned_fields:
+ @struct_attrs($($struct_attrs:tt)*),
+ @vis($vis:vis),
+ @name($name:ident),
+ @impl_generics($($impl_generics:tt)*),
+ @ty_generics($($ty_generics:tt)*),
+ @where($($whr:tt)*),
+ // We reached the end of the fields, plus an optional additional comma, since we added one
+ // before and the user is also allowed to put a trailing comma.
+ @fields_munch($(,)?),
+ @pinned($($pinned:tt)*),
+ @not_pinned($($not_pinned:tt)*),
+ @fields($($fields:tt)*),
+ @accum(),
+ @is_pinned(),
+ @pinned_drop($($pinned_drop:ident)?),
+ ) => {
+ // Declare the struct with all fields in the correct order.
+ $($struct_attrs)*
+ $vis struct $name <$($impl_generics)*>
+ where $($whr)*
+ {
+ $($fields)*
+ }
+
+ // We put the rest into this const item, because it then will not be accessible to anything
+ // outside.
+ const _: () = {
+ // We declare this struct which will host all of the projection function for our type.
+ // it will be invariant over all generic parameters which are inherited from the
+ // struct.
+ $vis struct __ThePinData<$($impl_generics)*>
+ where $($whr)*
+ {
+ __phantom: ::core::marker::PhantomData<
+ fn($name<$($ty_generics)*>) -> $name<$($ty_generics)*>
+ >,
+ }
+
+ impl<$($impl_generics)*> ::core::clone::Clone for __ThePinData<$($ty_generics)*>
+ where $($whr)*
+ {
+ fn clone(&self) -> Self { *self }
+ }
+
+ impl<$($impl_generics)*> ::core::marker::Copy for __ThePinData<$($ty_generics)*>
+ where $($whr)*
+ {}
+
+ // Make all projection functions.
+ $crate::__pin_data!(make_pin_data:
+ @pin_data(__ThePinData),
+ @impl_generics($($impl_generics)*),
+ @ty_generics($($ty_generics)*),
+ @where($($whr)*),
+ @pinned($($pinned)*),
+ @not_pinned($($not_pinned)*),
+ );
+
+ // SAFETY: We have added the correct projection functions above to `__ThePinData` and
+ // we also use the least restrictive generics possible.
+ unsafe impl<$($impl_generics)*>
+ $crate::init::__internal::HasPinData for $name<$($ty_generics)*>
+ where $($whr)*
+ {
+ type PinData = __ThePinData<$($ty_generics)*>;
+
+ unsafe fn __pin_data() -> Self::PinData {
+ __ThePinData { __phantom: ::core::marker::PhantomData }
+ }
+ }
+
+ unsafe impl<$($impl_generics)*>
+ $crate::init::__internal::PinData for __ThePinData<$($ty_generics)*>
+ where $($whr)*
+ {
+ type Datee = $name<$($ty_generics)*>;
+ }
+
+ // This struct will be used for the unpin analysis. Since only structurally pinned
+ // fields are relevant whether the struct should implement `Unpin`.
+ #[allow(dead_code)]
+ struct __Unpin <'__pin, $($impl_generics)*>
+ where $($whr)*
+ {
+ __phantom_pin: ::core::marker::PhantomData<fn(&'__pin ()) -> &'__pin ()>,
+ __phantom: ::core::marker::PhantomData<
+ fn($name<$($ty_generics)*>) -> $name<$($ty_generics)*>
+ >,
+ // Only the pinned fields.
+ $($pinned)*
+ }
+
+ #[doc(hidden)]
+ impl<'__pin, $($impl_generics)*> ::core::marker::Unpin for $name<$($ty_generics)*>
+ where
+ __Unpin<'__pin, $($ty_generics)*>: ::core::marker::Unpin,
+ $($whr)*
+ {}
+
+ // We need to disallow normal `Drop` implementation, the exact behavior depends on
+ // whether `PinnedDrop` was specified as the parameter.
+ $crate::__pin_data!(drop_prevention:
+ @name($name),
+ @impl_generics($($impl_generics)*),
+ @ty_generics($($ty_generics)*),
+ @where($($whr)*),
+ @pinned_drop($($pinned_drop)?),
+ );
+ };
+ };
+ // When no `PinnedDrop` was specified, then we have to prevent implementing drop.
+ (drop_prevention:
+ @name($name:ident),
+ @impl_generics($($impl_generics:tt)*),
+ @ty_generics($($ty_generics:tt)*),
+ @where($($whr:tt)*),
+ @pinned_drop(),
+ ) => {
+ // We prevent this by creating a trait that will be implemented for all types implementing
+ // `Drop`. Additionally we will implement this trait for the struct leading to a conflict,
+ // if it also implements `Drop`
+ trait MustNotImplDrop {}
+ #[allow(drop_bounds)]
+ impl<T: ::core::ops::Drop> MustNotImplDrop for T {}
+ impl<$($impl_generics)*> MustNotImplDrop for $name<$($ty_generics)*>
+ where $($whr)* {}
+ };
+ // If some other parameter was specified, we emit a readable error.
+ (drop_prevention:
+ @name($name:ident),
+ @impl_generics($($impl_generics:tt)*),
+ @ty_generics($($ty_generics:tt)*),
+ @where($($whr:tt)*),
+ @pinned_drop($($rest:tt)*),
+ ) => {
+ compile_error!(
+ "Wrong parameters to `#[pin_data]`, expected nothing or `PinnedDrop`, got '{}'.",
+ stringify!($($rest)*),
+ );
+ };
+ (make_pin_data:
+ @pin_data($pin_data:ident),
+ @impl_generics($($impl_generics:tt)*),
+ @ty_generics($($ty_generics:tt)*),
+ @where($($whr:tt)*),
+ @pinned($($(#[$($p_attr:tt)*])* $pvis:vis $p_field:ident : $p_type:ty),* $(,)?),
+ @not_pinned($($(#[$($attr:tt)*])* $fvis:vis $field:ident : $type:ty),* $(,)?),
+ ) => {
+ // For every field, we create a projection function according to its projection type. If a
+ // field is structurally pinned, then it must be initialized via `PinInit`, if it is not
+ // structurally pinned, then it can be initialized via `Init`.
+ //
+ // The functions are `unsafe` to prevent accidentally calling them.
+ #[allow(dead_code)]
+ impl<$($impl_generics)*> $pin_data<$($ty_generics)*>
+ where $($whr)*
+ {
+ $(
+ $pvis unsafe fn $p_field<E>(
+ self,
+ slot: *mut $p_type,
+ init: impl $crate::init::PinInit<$p_type, E>,
+ ) -> ::core::result::Result<(), E> {
+ unsafe { $crate::init::PinInit::__pinned_init(init, slot) }
+ }
+ )*
+ $(
+ $fvis unsafe fn $field<E>(
+ self,
+ slot: *mut $type,
+ init: impl $crate::init::Init<$type, E>,
+ ) -> ::core::result::Result<(), E> {
+ unsafe { $crate::init::Init::__init(init, slot) }
+ }
+ )*
+ }
+ };
+}