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//! Type checked partial references. //! //! This crate provides type checked partial references for rust. Type checked partial references //! are one solution to solve [interprocedural borrowing conflicts][interprocedural-conflicts]. //! //! # Tutorial //! //! With this crate it is possible to declare typed parts (using the [`part`] macro) and to assign //! struct fields to these parts (by [deriving `PartialRefTarget`](partial_ref_derive)). //! //! ``` //! use partial_ref::{part, PartialRefTarget}; //! //! part!(pub Neighbors: Vec<Vec<usize>>); //! part!(pub Colors: Vec<usize>); //! part!(pub Weights: Vec<f32>); //! //! #[derive(PartialRefTarget, Default)] //! pub struct Graph { //! #[part(Neighbors)] //! pub neighbors: Vec<Vec<usize>>, //! #[part(Colors)] //! pub colors: Vec<usize>, //! #[part(Weights)] //! pub weights: Vec<f32>, //! } //! ``` //! //! It is then possible to convert a reference to a value using the [`IntoPartialRef`] and //! [`IntoPartialRefMut`] traits, which are derived alongside PartialRefTarget. Note that a mutable //! partial reference must itself be mutable for mutable access. //! //! ``` //! # use partial_ref::{part, PartialRefTarget}; //! # use partial_ref_tests::doctest_helpers::*; //! use partial_ref::IntoPartialRefMut; //! //! let mut g = Graph::default(); //! //! let mut g_ref = g.into_partial_ref_mut(); //! ``` //! //! You can access parts using the [`part`](PartialRef::part) and [`part_mut`](PartialRef::part_mut) //! methods. //! //! ``` //! # use partial_ref::{part, PartialRefTarget, IntoPartialRefMut}; //! # use partial_ref_tests::doctest_helpers::*; //! # let mut g = Graph::default(); //! # let mut g_ref = g.into_partial_ref_mut(); //! use partial_ref::PartialRef; //! //! g_ref.part_mut(Colors).extend(&[0, 1, 0]); //! g_ref.part_mut(Weights).extend(&[0.25, 0.5, 0.75]); //! //! g_ref.part_mut(Neighbors).push(vec![1, 2]); //! g_ref.part_mut(Neighbors).push(vec![0, 2]); //! g_ref.part_mut(Neighbors).push(vec![0, 1]); //! //! assert_eq!(g_ref.part(Colors).len(), g_ref.part(Neighbors).len()); //! assert_eq!(g_ref.part(Colors).len(), g_ref.part(Weights).len()); //! ``` //! //! We can now write a function that takes parts of a reference. The type of such a partial //! reference can be written using the [`partial`] macro, which expands to a combination of [`Mut`], //! [`Const`] and [`Ref`]. Again the parameter `g` here must be mutable to allow mutable access to //! the referenced value. To call such a function we use the [`borrow`](PartialRef::borrow) method, //! which will re-borrow just the required parts. //! //! ``` //! # use partial_ref::{part, PartialRefTarget, IntoPartialRefMut, PartialRef}; //! # use partial_ref_tests::doctest_helpers::*; //! # let mut g = example_graph(); //! # let mut g_ref = g.into_partial_ref_mut(); //! use partial_ref::partial; //! //! pub fn add_color_to_weight( //! mut g: partial!(Graph, mut Weights, Colors), //! index: usize, //! ) { //! g.part_mut(Weights)[index] += g.part(Colors)[index] as f32; //! } //! //! add_color_to_weight(g_ref.borrow(), 1); //! //! assert_eq!(g_ref.part(Weights)[1], 1.5); //! ``` //! //! So far everything could have been written using plain built-in references. This changes as soon //! as we want to iterate over the neighbors while invoking our function. Usually we couldn't pass a //! mutable reference to the graph while holding the iterator over the neighbors. //! //! This can be easily done using partial references which support splitting. Splitting means //! turning a single reference into two references where each has a subset of parts, so that each //! mutably referenced part belongs only to a single reference. This is done by the //! [`split_borrow`](PartialRef::borrow) and [`split_part`](PartialRef::split_part) methods. //! //! ``` //! # use partial_ref::{part, PartialRefTarget, IntoPartialRefMut, PartialRef, partial}; //! # use partial_ref_tests::doctest_helpers::*; //! # let mut g = example_graph(); //! # let mut g_ref = g.into_partial_ref_mut(); //! let (neighbors, mut g_ref) = g_ref.split_part_mut(Neighbors); //! let (colors, mut g_ref) = g_ref.split_part(Colors); //! //! for (edges, &color) in neighbors.iter_mut().zip(colors.iter()) { //! edges.retain(|&neighbor| colors[neighbor] != color); //! //! for &neighbor in edges.iter() { //! add_color_to_weight(g_ref.borrow(), neighbor); //! } //! } //! ``` //! //! This covers the basic functionality of this library. Beyond that this library also supports: //! //! * Partial references to nested structs using [`Nested`] and [`nested_part`]. //! * Generic functions with bounds on available parts using [`HasPart`]. //! //! # Notes //! //! Some documented items are marked with *(internal)*. Typical code using this library doesn't //! explicitly refer to them. Nevertheless they often appear in error messages and are thus part of //! this documentation. These items also have to be public for the inference driven meta programming //! to work. Code that is generic over parts of partial references might also need them. //! //! Many traits in this crate are marked as unsafe without documenting any requirements for //! implementations. This does not mean they are safe to implement, but rather means that they are //! not intended to be implemented outside of this library. Feel free to file an issue if you have a //! good reason to implement them so the requirements can be documented. //! //! [interprocedural-conflicts]: http://smallcultfollowing.com/babysteps/blog/2018/11/01/after-nll-interprocedural-conflicts/ #[macro_use] mod macros; pub use partial_ref_derive::PartialRefTarget; use std::marker::PhantomData; /// A type that can be the target of partial references. /// /// Implementations for this trait should be derived, see [`partial_ref_derive`]. pub trait PartialRefTarget { /// A partial reference will be represented by a pointer to this associated type. /// /// In most cases this is the implementing type itself. This is not a requirement though. In the /// future, some features will introduce PartialRefTargets that have a different associated /// `RawTarget` type. type RawTarget: ?Sized; } /// Helper trait to associate the target type with a [`PartialRef`] without needing a lifetime. pub trait HasTarget { /// The referenced type. /// // TODO add a warning that Target::RawTarget could be != Target when such a feature lands) type Target: PartialRefTarget + ?Sized; } /// A partial reference. /// /// This is implemented by variants of [`Ref`], [`Mut`] and [`Const`]. This is only implemented if the /// parts of any contained [`Mut`] or [`Const`] are valid for the referenced type. pub trait PartialRef<'a>: HasTarget + Sized { /// Create a partial reference from a raw pointer. /// /// # Safety /// This is unsafe for two reasons. It can be used to dereference a raw pointer, which is /// already unsafe on its own, and it can be used to construct invalid partial references, for /// example containing the same mutable part twice. Thus extra care is required when calling /// this. unsafe fn from_raw(ptr: *mut <Self::Target as PartialRefTarget>::RawTarget) -> Self; /// Access to the underlying raw pointer. /// /// Beware that this can be used even for an empty reference with no parts. Doing anything with /// the resulting pointer is very likely unsafe, even if the partial reference is still in /// scope. fn get_raw(&self) -> *mut <Self::Target as PartialRefTarget>::RawTarget; /// Partially re-borrows a partial reference. /// /// This returns a new partial reference to the same value. The returned reference can have a /// subset of the original reference's parts. /// /// A typical use case is passing a reference to a function that requires fewer parts than the /// caller. /// /// Usually the type parameters can be inferred. #[inline(always)] fn borrow<BorrowedRef, SubsetIndex>(&'a mut self) -> BorrowedRef where BorrowedRef: PartialRef<'a, Target = Self::Target>, Self: HasSubset<'a, BorrowedRef, SubsetIndex>, { unsafe { BorrowedRef::from_raw(self.get_raw()) } } /// Access a part of the referenced value. /// /// This returns a plain reference to a single part. /// /// The parameter is only present for type inference, its value is ignored. As all parts /// implement [`Default`] it is always possible to pass a default value, which is useful in /// generic code. /// /// Usually the type parameters can be inferred. #[inline(always)] fn part<FieldPartSpec, FieldPart, PartIndex, FieldType>( &'a self, _part: FieldPartSpec, ) -> &'a FieldType where FieldType: ?Sized, FieldPart: Part<PartType = Field<FieldType>>, FieldPartSpec: PartSpec<FieldPart>, Self: PluckConst<'a, FieldPart, PartIndex>, Self::Target: HasPart<FieldPart> + 'a, { unsafe { <Const<FieldPart, Ref<'a, Self::Target>> as PartialRef<'a>>::from_raw(self.get_raw()) .get_part() } } /// Mutable access to a part of the referenced value. /// /// This returns a plain mutable reference to a single part. /// /// The parameter is only present for type inference, its value is ignored. As all parts /// implement [`Default`] it is always possible to pass a default value, which is useful in /// generic code. /// /// Usually the type parameters can be inferred. #[inline(always)] fn part_mut<FieldPartSpec, FieldPart, PartIndex, FieldType>( &'a mut self, _part: FieldPartSpec, ) -> &'a mut FieldType where FieldType: ?Sized, FieldPart: Part<PartType = Field<FieldType>>, FieldPartSpec: PartSpec<FieldPart>, Self: PluckMut<'a, FieldPart, PartIndex>, Self::Target: HasPart<FieldPart> + 'a, { unsafe { <Mut<FieldPart, Ref<'a, Self::Target>> as PartialRef<'a>>::from_raw(self.get_raw()) .get_part_mut() } } /// Partially re-borrows a partial reference, splitting off the remaining parts. /// /// This is equivalent to [`borrow`](PartialRef::borrow) but also returns a second partial /// reference that contains all parts that can be used simultaneously with the re-borrowed /// reference. /// /// This means that constant parts are contained in both references, while mutable parts that /// are re-borrowed are missing from the second partial reference. Mutable parts that are /// re-borrowed as constant parts are constant parts of both references. /// /// Usually the type parameters can be inferred. #[inline(always)] fn split_borrow<BorrowedRef, SubsetIndex>(&'a mut self) -> (BorrowedRef, Self::Remainder) where BorrowedRef: PartialRef<'a, Target = Self::Target>, Self: HasSubset<'a, BorrowedRef, SubsetIndex>, { let ptr = self.get_raw(); unsafe { (BorrowedRef::from_raw(ptr), Self::Remainder::from_raw(ptr)) } } /// Access a part of the referenced value, splitting off the remaining parts. /// /// This is equivalent to [`part`](PartialRef::part) but also returns a partial reference as /// described in [`split_borrow`](PartialRef::split_borrow). #[inline(always)] fn split_part<FieldPartSpec, FieldPart, PartIndex, FieldType>( &'a mut self, _part: FieldPartSpec, ) -> (&'a FieldType, Self::Remainder) where FieldType: ?Sized, FieldPart: Part<PartType = Field<FieldType>>, FieldPartSpec: PartSpec<FieldPart>, Self: PluckConst<'a, FieldPart, PartIndex>, Self::Target: HasPart<FieldPart> + 'a, { let ptr = self.get_raw(); unsafe { ( <Const<FieldPart, Ref<'a, Self::Target>> as PartialRef<'a>>::from_raw(ptr) .get_part(), Self::Remainder::from_raw(ptr), ) } } /// Mutable access to a part of the referenced value, splitting off the remaining parts. /// /// This is equivalent to [`part_mut`](PartialRef::part_mut) but also returns a partial /// reference as described in [`split_borrow`](PartialRef::split_borrow). #[inline(always)] fn split_part_mut<FieldPartSpec, FieldPart, PartIndex, FieldType>( &'a mut self, _part: FieldPartSpec, ) -> (&'a mut FieldType, Self::Remainder) where FieldType: ?Sized, FieldPart: Part<PartType = Field<FieldType>>, FieldPartSpec: PartSpec<FieldPart>, Self: PluckMut<'a, FieldPart, PartIndex>, Self::Target: HasPart<FieldPart> + 'a, { let ptr = self.get_raw(); unsafe { ( <Mut<FieldPart, Ref<'a, Self::Target>> as PartialRef<'a>>::from_raw(ptr) .get_part_mut(), Self::Remainder::from_raw(ptr), ) } } } /// Construction of partial references. /// /// See also [`IntoPartialRefMut`]. /// /// This trait gets an automatic implementation for references (mutable or immutable) to any type /// that has a derive statement for [`PartialRefTarget`]. Usually there is no need to implement this /// trait manually. pub trait IntoPartialRef<'a> { type Ref: PartialRef<'a>; /// Convert a mutable or immutable reference into a partial reference. fn into_partial_ref(self) -> Self::Ref; } /// Construction of partial references from mutable references. /// /// This has an implementation for mutable references that implement [`IntoPartialRefMut`]. It /// performs the same operation as [`IntoPartialRefMut`] but is only implemented for mutable /// references. This is useful as it allows writing `value.into_partial_ref_mut()` instead of `(&mut /// value).into_partial_ref_mut()` using auto referencing of method calls. Using just /// [`value.into_partial_ref()`] would result in an immutable reference. pub trait IntoPartialRefMut<'a>: IntoPartialRef<'a> { /// Convert a mutable reference into a partial reference. fn into_partial_ref_mut(self) -> Self::Ref; } impl<'a, T> IntoPartialRefMut<'a> for &'a mut T where Self: IntoPartialRef<'a>, { fn into_partial_ref_mut(self) -> Self::Ref { self.into_partial_ref() } } /// *(internal)* Split a part into nested parts. /// /// This is used to implement splitting of nested parts. pub unsafe trait SplitIntoParts<'a, ContainingPart, Reference: PartialRef<'a>> { /// A partial reference that has all the parts `Reference` and all parts of `Self` nested in /// `ContainingPart` as constant parts. type Result: PartialRef<'a, Target = Reference::Target>; /// A partial reference that has all the parts `Reference` and all parts of `Self` nested in /// `ContainingPart` as mutable parts. type ResultMut: PartialRef<'a, Target = Reference::Target>; } /// An empty partial reference borrowing no parts. /// /// Partial references with a non-empty set of borrowed parts are built by nesting this type within /// the [`Mut`] and [`Const`] types. #[repr(transparent)] pub struct Ref<'a, Target: PartialRefTarget + ?Sized> { ptr: *mut Target::RawTarget, phantom: PhantomData<&'a mut Target>, } impl<'a, Target: PartialRefTarget + ?Sized> HasTarget for Ref<'a, Target> { type Target = Target; } /// An empty reference to a valid target is a valid reference. impl<'a, 'b: 'a, Target: PartialRefTarget + ?Sized> PartialRef<'a> for Ref<'b, Target> { #[inline(always)] unsafe fn from_raw(ptr: *mut <Self::Target as PartialRefTarget>::RawTarget) -> Self { Ref { ptr, phantom: PhantomData, } } #[inline(always)] fn get_raw(&self) -> *mut <Self::Target as PartialRefTarget>::RawTarget { self.ptr } } /// An empty reference contains no mutable parts and thus is safe to clone. impl<'a, Target: PartialRefTarget> Copy for Ref<'a, Target> {} /// An empty reference contains no mutable parts and thus is safe to clone. impl<'a, Target: PartialRefTarget> Clone for Ref<'a, Target> { #[inline(always)] fn clone(&self) -> Self { *self } } /// A mutable part of a partial reference. #[repr(transparent)] pub struct Mut<Part, Reference: HasTarget> { ptr: *mut <<Reference as HasTarget>::Target as PartialRefTarget>::RawTarget, phantom: PhantomData<(Reference, Part)>, } impl<'a, SomePart: Part, Reference: PartialRef<'a>> HasTarget for Mut<SomePart, Reference> where Reference::Target: HasPart<SomePart>, { type Target = Reference::Target; } /// Extending a valid reference by a mutable part is still a valid reference when the reference /// target has such a part. impl<'a, SomePart: Part, Reference: PartialRef<'a>> PartialRef<'a> for Mut<SomePart, Reference> where Reference::Target: HasPart<SomePart>, { #[inline(always)] unsafe fn from_raw(ptr: *mut <Self::Target as PartialRefTarget>::RawTarget) -> Self { Mut { ptr, phantom: PhantomData, } } #[inline(always)] fn get_raw(&self) -> *mut <Self::Target as PartialRefTarget>::RawTarget { self.ptr } } /// A constant (immutable) part of a partial reference. #[repr(transparent)] pub struct Const<Part, Reference: HasTarget> { ptr: *mut <<Reference as HasTarget>::Target as PartialRefTarget>::RawTarget, phantom: PhantomData<(Reference, Part)>, } impl<'a, SomePart: Part, Reference: PartialRef<'a>> HasTarget for Const<SomePart, Reference> where Reference::Target: HasPart<SomePart>, { type Target = Reference::Target; } /// Extending a valid reference by a constant part is still a valid reference when the reference /// target has such a part. impl<'a, SomePart: Part, Reference: PartialRef<'a>> PartialRef<'a> for Const<SomePart, Reference> where Reference::Target: HasPart<SomePart>, { #[inline(always)] unsafe fn from_raw(ptr: *mut <Self::Target as PartialRefTarget>::RawTarget) -> Self { Const { ptr, phantom: PhantomData, } } #[inline(always)] fn get_raw(&self) -> *mut <Self::Target as PartialRefTarget>::RawTarget { self.ptr } } /// A reference containing just constant parts is safe to clone. impl<SomePart, Reference: Copy + HasTarget> Copy for Const<SomePart, Reference> {} /// A reference containing just constant parts is safe to clone. impl<SomePart, Reference: Copy + HasTarget> Clone for Const<SomePart, Reference> { #[inline(always)] fn clone(&self) -> Self { *self } } impl<'a, SomePart, Target, FieldType> Const<SomePart, Ref<'a, Target>> where FieldType: ?Sized, SomePart: Part<PartType = Field<FieldType>>, Target: ?Sized, Target: HasPart<SomePart>, { /// Only available on single part references, used to implement the more general /// [`part`](PartialRef::part) method of [`PartialRef`]. #[inline(always)] fn get_part(self) -> &'a FieldType { unsafe { &*Target::part_ptr(self.get_raw() as *const _) } } } impl<'a, SomePart, Target, FieldType> Mut<SomePart, Ref<'a, Target>> where FieldType: ?Sized, SomePart: Part<PartType = Field<FieldType>>, Target: ?Sized, Target: HasPart<SomePart>, { /// Only available on single part references, used to implement the more general /// [`part_mut`](PartialRef::part_mut) method of [`PartialRef`] #[inline(always)] fn get_part_mut(self) -> &'a mut FieldType { unsafe { &mut *Target::part_ptr_mut(self.get_raw()) } } } // Parts /// Marker types for a part of a type. /// /// Types implementing this trait are usually created using the [`part`] macro. /// /// A type implementing this trait is used to identify a part of a reference target. Multiple /// different reference targets can have a part identified by the same [`Part`] (see also /// [`HasPart`]). A part has an associated [`PartType`], which determines what can be done with a /// part. pub trait Part: Default { type PartType: PartType; } /// Helper trait to strip lifetimes from a part. /// /// Every part `SomePart<'a, ...>` should implement `PartSpec<SomePart<'b, ...>>`. This is used by /// the [`part`](PartialRef::part), [`part_mut`](PartialRef::part_mut), /// [`split_part`](PartialRef::split_part) and [`split_part_mut`](PartialRef::split_part_mut) /// functions. This allows the passed parameter to have a different lifetime than the accessed part. /// This in turn enables part selection using globals with static lifetimes as declared by the /// [`part`] macro. pub trait PartSpec<Part> {} /// Implemented when a reference target has a part. /// /// This trait provides methods for unchecked access to a part of a reference target. /// Implementations for this are automatically created when deriving PartialRefTarget. pub trait HasPart<SomePart: Part>: PartialRefTarget { /// Given a constant pointer to a target, produce a constant pointer to a part of it. /// /// # Safety /// Implementations may construct a temporary reference to ptr, which thus must be valid. unsafe fn part_ptr(ptr: *const Self::RawTarget) -> <SomePart::PartType as PartType>::Ptr; /// Given a mutable pointer to a target, produce a mutable pointer to a part of it. /// /// # Safety /// Implementations may construct a temporary reference to ptr, which thus must be valid. unsafe fn part_ptr_mut(ptr: *mut Self::RawTarget) -> <SomePart::PartType as PartType>::PtrMut; } /// Type of a part, determines what can be done with a part. /// /// Common part types are [`Field`] and [`AbstractPart`]. pub trait PartType { /// Type that can be produced from a constant pointer to a reference target. type Ptr; /// Type that can be produced from a mutable pointer to a reference target. type PtrMut; } /// Type of a part that corresponds to a struct field. /// /// Partial references containing a part of this type provide access to that field. pub struct Field<FieldType: ?Sized>(PhantomData<FieldType>); impl<FieldType: ?Sized> PartType for Field<FieldType> { type Ptr = *const FieldType; type PtrMut = *mut FieldType; } /// Type of an abstract part. /// /// Partial reference keep track of an abstract part, without providing any operations on it. pub struct AbstractPart; impl PartType for AbstractPart { type Ptr = (); type PtrMut = (); } /// A nested part. /// /// A nested part can be constructed from an outer part and an inner part. The outer part must be a /// [`Field`] part, and the field's type must be a [`PartialRefTarget`] having the the inner part /// ([`HasPart`]). /// /// When nesting multiple times, the nested part should always be the outer part. This isn't /// enforced, but some operations are only supported in that case. #[derive(Default)] pub struct Nested<Outer, Inner>(Outer, Inner); /// Create default values for nested parts. /// /// These are useful as parameters to pass to [`PartialRef`]'s part functions. impl<NewInnerPart: Part, Outer: Part, Inner: Part> std::ops::BitOr<NewInnerPart> for Nested<Outer, Inner> { type Output = Nested<Nested<Outer, Inner>, NewInnerPart>; fn bitor(self, _rhs: NewInnerPart) -> Self::Output { std::default::Default::default() } } /// A nested part is itself a part. impl<Outer, OuterFieldType, Inner> Part for Nested<Outer, Inner> where Outer: Part<PartType = Field<OuterFieldType>>, Inner: Part, OuterFieldType: ?Sized, OuterFieldType: HasPart<Inner>, OuterFieldType: PartialRefTarget<RawTarget = OuterFieldType>, { type PartType = Inner::PartType; } impl<Outer, Inner, OuterS, InnerS> PartSpec<Nested<OuterS, InnerS>> for Nested<Outer, Inner> where Outer: PartSpec<OuterS>, Inner: PartSpec<InnerS>, { } /// A reference has a nested part if it has the outer part and the nested part is valid. impl<Reference, Outer, OuterFieldType, Inner> HasPart<Nested<Outer, Inner>> for Reference where Reference: ?Sized, Reference: HasPart<Outer>, Outer: Part<PartType = Field<OuterFieldType>>, Inner: Part, OuterFieldType: ?Sized, OuterFieldType: HasPart<Inner>, OuterFieldType: PartialRefTarget<RawTarget = OuterFieldType>, { #[inline(always)] unsafe fn part_ptr(ptr: *const Self::RawTarget) -> <Inner::PartType as PartType>::Ptr { <OuterFieldType as HasPart<Inner>>::part_ptr(<Self as HasPart<Outer>>::part_ptr(ptr)) } #[inline(always)] unsafe fn part_ptr_mut(ptr: *mut Self::RawTarget) -> <Inner::PartType as PartType>::PtrMut { <OuterFieldType as HasPart<Inner>>::part_ptr_mut(<Self as HasPart<Outer>>::part_ptr_mut( ptr, )) } } // Type level logic for subsetting // This is inspired by the `frunk` crate /// *(internal)* Select the first part. pub struct IndexHere; /// *(internal)* Skip the first part. pub struct IndexNext<Index>(Index); /// *(internal)* Split the first part. pub struct IndexSplit<NestedPartIndex, Index>(NestedPartIndex, Index); /// *(internal)* Extracts the constant part `PluckedPart` at position `Index` from the partial /// reference having this trait, leaving `Self::Remainder`. /// /// Plucking a constant part still leaves the part in the remaining reference, but will change it /// from mutable to constant. /// /// The `Index` type can be inferred. pub unsafe trait PluckConst<'a, PluckedPart, Index>: PartialRef<'a> { /// The partial reference left after plucking. type Remainder: PartialRef<'a, Target = Self::Target>; } /// *(internal)* Extracts the mutable part `PluckedPart` at position `Index` from the partial /// reference having this trait, leaving `Self::Remainder`. /// /// Plucking a mutable part removes it from the remaining reference. /// /// The `Index` type can be inferred. pub unsafe trait PluckMut<'a, PluckedPart, Index>: PartialRef<'a> { /// The partial reference left after plucking. type Remainder: PartialRef<'a, Target = Self::Target>; } /// *(internal)* Plucks the outermost constant part. unsafe impl<'a, PluckedPart, Reference> PluckConst<'a, PluckedPart, IndexHere> for Const<PluckedPart, Reference> where PluckedPart: Part, Reference: PartialRef<'a>, Reference::Target: HasPart<PluckedPart>, { type Remainder = Const<PluckedPart, Reference>; } /// *(internal)* Plucks the first part, converting it from mutable to constant. unsafe impl<'a, PluckedPart, Reference> PluckConst<'a, PluckedPart, IndexHere> for Mut<PluckedPart, Reference> where PluckedPart: Part, Reference: PartialRef<'a>, Reference::Target: HasPart<PluckedPart>, { type Remainder = Const<PluckedPart, Reference>; } /// *(internal)* Plucks the first mutable part. unsafe impl<'a, PluckedPart, Reference> PluckMut<'a, PluckedPart, IndexHere> for Mut<PluckedPart, Reference> where PluckedPart: Part, Reference: PartialRef<'a>, Reference::Target: HasPart<PluckedPart>, { type Remainder = Reference; } /// *(internal)* Skips the constant first part while plucking a constant part. unsafe impl<'a, PluckedPart, SkippedPart, Reference, Index> PluckConst<'a, PluckedPart, IndexNext<Index>> for Const<SkippedPart, Reference> where PluckedPart: Part, SkippedPart: Part, Reference::Target: HasPart<PluckedPart>, Reference::Target: HasPart<SkippedPart>, Reference: PluckConst<'a, PluckedPart, Index>, { type Remainder = Const<SkippedPart, Reference::Remainder>; } /// *(internal)* Skips the mutable first part while plucking a constant part. unsafe impl<'a, PluckedPart, SkippedPart, Reference, Index> PluckConst<'a, PluckedPart, IndexNext<Index>> for Mut<SkippedPart, Reference> where PluckedPart: Part, SkippedPart: Part, Reference::Target: HasPart<PluckedPart>, Reference::Target: HasPart<SkippedPart>, Reference: PluckConst<'a, PluckedPart, Index>, { type Remainder = Mut<SkippedPart, Reference::Remainder>; } /// *(internal)* Skips the constant first part while plucking a mutable part. unsafe impl<'a, PluckedPart, SkippedPart, Reference, Index> PluckMut<'a, PluckedPart, IndexNext<Index>> for Const<SkippedPart, Reference> where PluckedPart: Part, SkippedPart: Part, Reference::Target: HasPart<PluckedPart>, Reference::Target: HasPart<SkippedPart>, Reference: PluckMut<'a, PluckedPart, Index>, { type Remainder = Const<SkippedPart, Reference::Remainder>; } /// *(internal)* Skips the mutable first part while plucking a mutable part. unsafe impl<'a, PluckedPart, SkippedPart, Reference, Index> PluckMut<'a, PluckedPart, IndexNext<Index>> for Mut<SkippedPart, Reference> where PluckedPart: Part, SkippedPart: Part, Reference::Target: HasPart<PluckedPart>, Reference::Target: HasPart<SkippedPart>, Reference: PluckMut<'a, PluckedPart, Index>, { type Remainder = Mut<SkippedPart, Reference::Remainder>; } /// *(internal)* Pluck a mutable nested subpart of the mutable first part. /// /// This leaves all other subparts in the remaining reference. unsafe impl< 'a, ContainingPart, PluckedOuter, PluckedInner, Reference, NestedPartIndex, Index, OuterFieldType, ContainingFieldType, > PluckMut<'a, Nested<PluckedOuter, PluckedInner>, IndexSplit<NestedPartIndex, Index>> for Mut<ContainingPart, Reference> where PluckedOuter: Part<PartType = Field<OuterFieldType>>, PluckedInner: Part, ContainingPart: Part<PartType = Field<ContainingFieldType>>, ContainingFieldType: SplitIntoParts<'a, ContainingPart, Reference>, ContainingFieldType: ?Sized, ContainingFieldType::ResultMut: PluckMut<'a, Nested<PluckedOuter, PluckedInner>, Index>, OuterFieldType: ?Sized, OuterFieldType: HasPart<PluckedInner>, OuterFieldType: PartialRefTarget<RawTarget = OuterFieldType>, Reference: PartialRef<'a>, Reference::Target: HasPart<ContainingPart>, ContainingPart: ContainsNestedPart<PluckedOuter, NestedPartIndex>, { type Remainder = <ContainingFieldType::ResultMut as PluckMut< 'a, Nested<PluckedOuter, PluckedInner>, Index, >>::Remainder; } /// *(internal)* Pluck a constant nested subpart of the mutable first part. /// /// This leaves all other subparts as mutable in the remaining reference. unsafe impl< 'a, ContainingPart, PluckedOuter, PluckedInner, Reference, NestedPartIndex, Index, OuterFieldType, ContainingFieldType, > PluckConst<'a, Nested<PluckedOuter, PluckedInner>, IndexSplit<NestedPartIndex, Index>> for Mut<ContainingPart, Reference> where PluckedOuter: Part<PartType = Field<OuterFieldType>>, PluckedInner: Part, ContainingPart: Part<PartType = Field<ContainingFieldType>>, ContainingFieldType: SplitIntoParts<'a, ContainingPart, Reference>, ContainingFieldType: ?Sized, ContainingFieldType::ResultMut: PluckConst<'a, Nested<PluckedOuter, PluckedInner>, Index>, OuterFieldType: ?Sized, OuterFieldType: HasPart<PluckedInner>, OuterFieldType: PartialRefTarget<RawTarget = OuterFieldType>, Reference: PartialRef<'a>, Reference::Target: HasPart<ContainingPart>, ContainingPart: ContainsNestedPart<PluckedOuter, NestedPartIndex>, { type Remainder = <ContainingFieldType::ResultMut as PluckConst< 'a, Nested<PluckedOuter, PluckedInner>, Index, >>::Remainder; } /// *(internal)* Pluck a constant nested subpart of the constant first part. unsafe impl< 'a, ContainingPart, PluckedOuter, PluckedInner, Reference, NestedPartIndex, Index, OuterFieldType, ContainingFieldType, > PluckConst<'a, Nested<PluckedOuter, PluckedInner>, IndexSplit<NestedPartIndex, Index>> for Const<ContainingPart, Reference> where PluckedOuter: Part<PartType = Field<OuterFieldType>>, PluckedInner: Part, ContainingPart: Part<PartType = Field<ContainingFieldType>>, ContainingFieldType: SplitIntoParts<'a, ContainingPart, Reference>, ContainingFieldType: ?Sized, ContainingFieldType::ResultMut: PluckConst<'a, Nested<PluckedOuter, PluckedInner>, Index>, OuterFieldType: ?Sized, OuterFieldType: HasPart<PluckedInner>, OuterFieldType: PartialRefTarget<RawTarget = OuterFieldType>, Reference: PartialRef<'a>, Reference::Target: HasPart<ContainingPart>, ContainingPart: ContainsNestedPart<PluckedOuter, NestedPartIndex>, { type Remainder = Const<ContainingPart, Reference>; } /// *(internal)* Index for the empty subset. pub struct SubsetIndexEnd; /// *(internal)* Construct a subset index from a part index and another subset index. pub struct SubsetIndexCons<PartIndex, TailIndex>(PartIndex, TailIndex); /// *(internal)* Asserts that the parts of the partial reference `Reference` are a subset of the /// parts of the partial reference having this trait. /// /// A list of parts is considered a subset if they can be plucked in sequence. pub unsafe trait HasSubset<'a, Reference, SubsetIndex>: PartialRef<'a> { type Remainder: PartialRef<'a, Target = Self::Target>; } /// *(internal)* Every reference has the empty reference as subset. unsafe impl<'a, Reference> HasSubset<'a, Ref<'a, Reference::Target>, SubsetIndexEnd> for Reference where Reference: PartialRef<'a>, { type Remainder = Reference; } /// *(internal)* To have a reference with a constant first part as subset, pluck that part and make /// sure the remaining references are in a subset relation. unsafe impl<'a, SubsetPart, Reference, PluckedRef, PartIndex, TailIndex> HasSubset<'a, Const<SubsetPart, Reference>, SubsetIndexCons<PartIndex, TailIndex>> for PluckedRef where PluckedRef: PluckConst<'a, SubsetPart, PartIndex>, <PluckedRef as PluckConst<'a, SubsetPart, PartIndex>>::Remainder: HasSubset<'a, Reference, TailIndex>, Reference: HasTarget, { type Remainder = <<PluckedRef as PluckConst<'a, SubsetPart, PartIndex>>::Remainder as HasSubset< 'a, Reference, TailIndex, >>::Remainder; } /// *(internal)* To have a reference with a mutable first part as subset, pluck that part and make /// sure the remaining references are in a subset relation. unsafe impl<'a, SubsetPart, Reference, PluckedRef, PartIndex, TailIndex> HasSubset<'a, Mut<SubsetPart, Reference>, SubsetIndexCons<PartIndex, TailIndex>> for PluckedRef where PluckedRef: PluckMut<'a, SubsetPart, PartIndex>, <PluckedRef as PluckMut<'a, SubsetPart, PartIndex>>::Remainder: HasSubset<'a, Reference, TailIndex>, Reference: HasTarget, { type Remainder = <<PluckedRef as PluckMut<'a, SubsetPart, PartIndex>>::Remainder as HasSubset< 'a, Reference, TailIndex, >>::Remainder; } // Nesting helpers /// *(internal)* Check whether a part is nested inside another part. pub trait ContainsNestedPart<NestedPart, Index>: Part {} /// *(internal)* A part contains itself as a nested part. impl<NestedPart> ContainsNestedPart<NestedPart, IndexHere> for NestedPart where NestedPart: Part {} /// *(internal)* A part contains a nested part if it contains the outer part of the nested part. impl<NestedPart, Outer, Inner, OuterFieldType, Index> ContainsNestedPart<Nested<Outer, Inner>, IndexNext<Index>> for NestedPart where NestedPart: Part, Inner: Part, NestedPart: ContainsNestedPart<Outer, Index>, Outer: Part<PartType = Field<OuterFieldType>>, OuterFieldType: ?Sized, OuterFieldType: HasPart<Inner>, OuterFieldType: PartialRefTarget<RawTarget = OuterFieldType>, { }