Rollup merge of rust-lang#155034 - ChayimFriedman2:ra-fixes, r=lcnr

Implement `GenericTypeVisitable` for some types

This is required for rust-analyzer.

r? types

Author: JonathanBrouwer

compiler/rustc_type_ir/src/binder.rs

@@ -956,7 +956,7 @@ pub enum BoundVarIndexKind {
 /// identified by both a universe, as well as a name residing within that universe. Distinct bound
 /// regions/types/consts within the same universe simply have an unknown relationship to one
 #[derive_where(Clone, Copy, PartialOrd, Ord, PartialEq, Eq, Hash; I: Interner, T)]
-#[derive(TypeVisitable_Generic, TypeFoldable_Generic)]
+#[derive(TypeVisitable_Generic, TypeFoldable_Generic, GenericTypeVisitable)]
 #[cfg_attr(
     feature = "nightly",
     derive(Encodable_NoContext, Decodable_NoContext, HashStable_NoContext)
@@ -995,7 +995,7 @@ where
 }
 
 #[derive_where(Clone, Copy, PartialEq, Eq, Hash; I: Interner)]
-#[derive(Lift_Generic)]
+#[derive(Lift_Generic, GenericTypeVisitable)]
 #[cfg_attr(
     feature = "nightly",
     derive(Encodable_NoContext, Decodable_NoContext, HashStable_NoContext)
@@ -1058,7 +1058,7 @@ impl<I: Interner> BoundRegionKind<I> {
 }
 
 #[derive_where(Clone, Copy, PartialEq, Eq, Debug, Hash; I: Interner)]
-#[derive(Lift_Generic)]
+#[derive(Lift_Generic, GenericTypeVisitable)]
 #[cfg_attr(
     feature = "nightly",
     derive(Encodable_NoContext, Decodable_NoContext, HashStable_NoContext)
@@ -1069,7 +1069,7 @@ pub enum BoundTyKind<I: Interner> {
 }
 
 #[derive_where(Clone, Copy, PartialEq, Eq, Debug, Hash; I: Interner)]
-#[derive(Lift_Generic)]
+#[derive(Lift_Generic, GenericTypeVisitable)]
 #[cfg_attr(
     feature = "nightly",
     derive(Encodable_NoContext, Decodable_NoContext, HashStable_NoContext)
@@ -1104,6 +1104,7 @@ impl<I: Interner> BoundVariableKind<I> {
 }
 
 #[derive_where(Clone, Copy, PartialEq, Eq, Hash; I: Interner)]
+#[derive(GenericTypeVisitable)]
 #[cfg_attr(
     feature = "nightly",
     derive(Encodable_NoContext, HashStable_NoContext, Decodable_NoContext)
@@ -1164,6 +1165,7 @@ impl<I: Interner> PlaceholderRegion<I> {
 }
 
 #[derive_where(Clone, Copy, PartialEq, Eq, Hash; I: Interner)]
+#[derive(GenericTypeVisitable)]
 #[cfg_attr(
     feature = "nightly",
     derive(Encodable_NoContext, Decodable_NoContext, HashStable_NoContext)
@@ -1229,6 +1231,7 @@ impl<I: Interner> PlaceholderType<I> {
 }
 
 #[derive_where(Clone, Copy, PartialEq, Debug, Eq, Hash; I: Interner)]
+#[derive(GenericTypeVisitable)]
 #[cfg_attr(
     feature = "nightly",
     derive(Encodable_NoContext, Decodable_NoContext, HashStable_NoContext)

compiler/rustc_type_ir/src/const_kind.rs

@@ -141,7 +141,7 @@ impl<Hcx> HashStable<Hcx> for InferConst {
 /// `ValTree` does not have this problem with representation, as it only contains integers or
 /// lists of (nested) `ty::Const`s (which may indirectly contain more `ValTree`s).
 #[derive_where(Clone, Copy, Debug, Hash, Eq, PartialEq; I: Interner)]
-#[derive(TypeVisitable_Generic, TypeFoldable_Generic)]
+#[derive(TypeVisitable_Generic, TypeFoldable_Generic, GenericTypeVisitable)]
 #[cfg_attr(
     feature = "nightly",
     derive(Decodable_NoContext, Encodable_NoContext, HashStable_NoContext)

compiler/rustc_type_ir/src/generic_visit.rs

@@ -1,45 +1,13 @@
-//! A visiting traversal mechanism for complex data structures that contain type
-//! information.
+//! Special visiting used by rust-analyzer only.
 //!
-//! This is a read-only traversal of the data structure.
+//! It is different from `TypeVisitable` in two ways:
 //!
-//! 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 traits involved in each traversal.
-//! - `GenericTypeVisitable`. 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 recursive types of
-//!   interest, and defines the visiting "skeleton" for these types. (This
-//!   excludes `Region` because it is non-recursive, i.e. it never contains
-//!   other types of interest.)
-//! - `CustomizableTypeVisitor`. 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 `GenericTypeVisitable` impls handle most of the traversal, and call into
-//!   `CustomizableTypeVisitor` when they encounter a type of interest.
-//! - A `CustomizableTypeVisitor` may call into another `GenericTypeVisitable` impl, because some of
-//!   the types of interest are recursive and can contain other types of interest.
-//! - A `CustomizableTypeVisitor` 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: GenericTypeVisitable` and `U:
-//! GenericTypeVisitable`, and an instance `s = S(ty, u)`, it would be visited like so:
-//! ```text
-//! s.generic_visit_with(visitor) calls
-//! - ty.generic_visit_with(visitor) calls
-//!   - visitor.visit_ty(ty) may call
-//!     - ty.super_generic_visit_with(visitor)
-//! - u.generic_visit_with(visitor)
-//! ```
+//!  - The visitor is a generic of the trait and not the method, allowing types to attach
+//!    special behavior to visitors (as long as they know it; we don't use this capability
+//!    in rustc crates, but rust-analyzer needs it).
+//!  - It **must visit** every field. This is why we don't have an attribute like `#[type_visitable(ignore)]`
+//!    for this visit. The reason for this is soundness: rust-analyzer uses this visit to
+//!    garbage collect types, so a missing field can mean a use after free
 
 use std::sync::Arc;
 
@@ -53,16 +21,6 @@ use thin_vec::ThinVec;
 /// To implement this conveniently, use the derive macro located in
 /// `rustc_macros`.
 pub trait GenericTypeVisitable<V> {
-    /// The entry point for visiting. To visit a value `t` with a visitor `v`
-    /// call: `t.generic_visit_with(v)`.
-    ///
-    /// For most types, this just traverses the value, calling `generic_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 `GenericTypeVisitable` to
-    /// `CustomizableTypeVisitor`.
     fn generic_visit_with(&self, visitor: &mut V);
 }
 
@@ -216,6 +174,10 @@ macro_rules! trivial_impls {
     };
 }
 
+impl<T: ?Sized, V> GenericTypeVisitable<V> for std::marker::PhantomData<T> {
+    fn generic_visit_with(&self, _visitor: &mut V) {}
+}
+
 trivial_impls!(
     (),
     rustc_ast_ir::Mutability,