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author | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-17 12:19:41 +0000 |
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committer | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-17 12:19:41 +0000 |
commit | 4f9fe856a25ab29345b90e7725509e9ee38a37be (patch) | |
tree | e4ffd8a9374cae7b21f7cbfb352927e0e074aff6 /compiler/rustc_type_ir/src/visit.rs | |
parent | Adding upstream version 1.68.2+dfsg1. (diff) | |
download | rustc-4f9fe856a25ab29345b90e7725509e9ee38a37be.tar.xz rustc-4f9fe856a25ab29345b90e7725509e9ee38a37be.zip |
Adding upstream version 1.69.0+dfsg1.upstream/1.69.0+dfsg1
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to '')
-rw-r--r-- | compiler/rustc_type_ir/src/visit.rs | 115 |
1 files changed, 115 insertions, 0 deletions
diff --git a/compiler/rustc_type_ir/src/visit.rs b/compiler/rustc_type_ir/src/visit.rs new file mode 100644 index 000000000..62239fd20 --- /dev/null +++ b/compiler/rustc_type_ir/src/visit.rs @@ -0,0 +1,115 @@ +//! A visiting traversal mechanism for complex data structures that contain type +//! information. +//! +//! This is a read-only traversal of the data structure. +//! +//! This traversal has limited flexibility. Only a small number of "types of +//! interest" within the complex data structures can receive custom +//! visitation. These are the ones containing the most important type-related +//! information, such as `Ty`, `Predicate`, `Region`, and `Const`. +//! +//! There are three groups of traits involved in each traversal. +//! - `TypeVisitable`. This is implemented once for many types, including: +//! - Types of interest, for which the methods delegate to the visitor. +//! - All other types, including generic containers like `Vec` and `Option`. +//! It defines a "skeleton" of how they should be visited. +//! - `TypeSuperVisitable`. This is implemented only for each type of interest, +//! and defines the visiting "skeleton" for these types. +//! - `TypeVisitor`. This is implemented for each visitor. This defines how +//! types of interest are visited. +//! +//! This means each visit is a mixture of (a) generic visiting operations, and (b) +//! custom visit operations that are specific to the visitor. +//! - The `TypeVisitable` impls handle most of the traversal, and call into +//! `TypeVisitor` when they encounter a type of interest. +//! - A `TypeVisitor` may call into another `TypeVisitable` impl, because some of +//! the types of interest are recursive and can contain other types of interest. +//! - A `TypeVisitor` may also call into a `TypeSuperVisitable` impl, because each +//! visitor might provide custom handling only for some types of interest, or +//! only for some variants of each type of interest, and then use default +//! traversal for the remaining cases. +//! +//! For example, if you have `struct S(Ty, U)` where `S: TypeVisitable` and `U: +//! TypeVisitable`, and an instance `s = S(ty, u)`, it would be visited like so: +//! ```text +//! s.visit_with(visitor) calls +//! - ty.visit_with(visitor) calls +//! - visitor.visit_ty(ty) may call +//! - ty.super_visit_with(visitor) +//! - u.visit_with(visitor) +//! ``` +use crate::Interner; + +use std::fmt; +use std::ops::ControlFlow; + +/// This trait is implemented for every type that can be visited, +/// providing the skeleton of the traversal. +/// +/// To implement this conveniently, use the derive macro located in +/// `rustc_macros`. +pub trait TypeVisitable<I: Interner>: fmt::Debug + Clone { + /// The entry point for visiting. To visit a value `t` with a visitor `v` + /// call: `t.visit_with(v)`. + /// + /// For most types, this just traverses the value, calling `visit_with` on + /// each field/element. + /// + /// For types of interest (such as `Ty`), the implementation of this method + /// that calls a visitor method specifically for that type (such as + /// `V::visit_ty`). This is where control transfers from `TypeFoldable` to + /// `TypeVisitor`. + fn visit_with<V: TypeVisitor<I>>(&self, visitor: &mut V) -> ControlFlow<V::BreakTy>; +} + +pub trait TypeSuperVisitable<I: Interner>: TypeVisitable<I> { + /// Provides a default visit for a type of interest. This should only be + /// called within `TypeVisitor` methods, when a non-custom traversal is + /// desired for the value of the type of interest passed to that method. + /// For example, in `MyVisitor::visit_ty(ty)`, it is valid to call + /// `ty.super_visit_with(self)`, but any other visiting should be done + /// with `xyz.visit_with(self)`. + fn super_visit_with<V: TypeVisitor<I>>(&self, visitor: &mut V) -> ControlFlow<V::BreakTy>; +} + +/// This trait is implemented for every visiting traversal. There is a visit +/// method defined for every type of interest. Each such method has a default +/// that recurses into the type's fields in a non-custom fashion. +pub trait TypeVisitor<I: Interner>: Sized { + type BreakTy = !; + + fn visit_binder<T: TypeVisitable<I>>(&mut self, t: &I::Binder<T>) -> ControlFlow<Self::BreakTy> + where + I::Binder<T>: TypeSuperVisitable<I>, + { + t.super_visit_with(self) + } + + fn visit_ty(&mut self, t: I::Ty) -> ControlFlow<Self::BreakTy> + where + I::Ty: TypeSuperVisitable<I>, + { + t.super_visit_with(self) + } + + fn visit_region(&mut self, r: I::Region) -> ControlFlow<Self::BreakTy> + where + I::Region: TypeSuperVisitable<I>, + { + r.super_visit_with(self) + } + + fn visit_const(&mut self, c: I::Const) -> ControlFlow<Self::BreakTy> + where + I::Const: TypeSuperVisitable<I>, + { + c.super_visit_with(self) + } + + fn visit_predicate(&mut self, p: I::Predicate) -> ControlFlow<Self::BreakTy> + where + I::Predicate: TypeSuperVisitable<I>, + { + p.super_visit_with(self) + } +} |