Add #[derive(TypeVisitable)]

compiler/rustc_infer/src/infer/mod.rs

@@ -318,7 +318,7 @@ pub struct InferCtxt<'a, 'tcx> {
 }
 
 /// See the `error_reporting` module for more details.
-#[derive(Clone, Copy, Debug, PartialEq, Eq, TypeFoldable)]
+#[derive(Clone, Copy, Debug, PartialEq, Eq, TypeFoldable, TypeVisitable)]
 pub enum ValuePairs<'tcx> {
     Regions(ExpectedFound<ty::Region<'tcx>>),
     Terms(ExpectedFound<ty::Term<'tcx>>),

compiler/rustc_infer/src/infer/region_constraints/mod.rs

@@ -165,7 +165,7 @@ pub struct Verify<'tcx> {
     pub bound: VerifyBound<'tcx>,
 }
 
-#[derive(Copy, Clone, PartialEq, Eq, Hash, TypeFoldable)]
+#[derive(Copy, Clone, PartialEq, Eq, Hash, TypeFoldable, TypeVisitable)]
 pub enum GenericKind<'tcx> {
     Param(ty::ParamTy),
     Projection(ty::ProjectionTy<'tcx>),
@@ -272,7 +272,7 @@ pub enum VerifyBound<'tcx> {
 ///     }
 /// }
 /// ```
-#[derive(Debug, Copy, Clone, TypeFoldable)]
+#[derive(Debug, Copy, Clone, TypeFoldable, TypeVisitable)]
 pub struct VerifyIfEq<'tcx> {
     /// Type which must match the generic `G`
     pub ty: Ty<'tcx>,

compiler/rustc_infer/src/traits/project.rs

@@ -20,7 +20,7 @@ pub struct MismatchedProjectionTypes<'tcx> {
     pub err: ty::error::TypeError<'tcx>,
 }
 
-#[derive(Clone, TypeFoldable)]
+#[derive(Clone, TypeFoldable, TypeVisitable)]
 pub struct Normalized<'tcx, T> {
     pub value: T,
     pub obligations: Vec<PredicateObligation<'tcx>>,

compiler/rustc_macros/src/lib.rs

@@ -18,6 +18,7 @@ mod query;
 mod serialize;
 mod symbols;
 mod type_foldable;
+mod type_visitable;
 
 #[proc_macro]
 pub fn rustc_queries(input: TokenStream) -> TokenStream {
@@ -121,6 +122,7 @@ decl_derive!([TyEncodable] => serialize::type_encodable_derive);
 decl_derive!([MetadataDecodable] => serialize::meta_decodable_derive);
 decl_derive!([MetadataEncodable] => serialize::meta_encodable_derive);
 decl_derive!([TypeFoldable, attributes(type_foldable)] => type_foldable::type_foldable_derive);
+decl_derive!([TypeVisitable, attributes(type_visitable)] => type_visitable::type_visitable_derive);
 decl_derive!([Lift, attributes(lift)] => lift::lift_derive);
 decl_derive!(
     [SessionDiagnostic, attributes(

compiler/rustc_macros/src/type_foldable.rs

@@ -11,11 +11,6 @@ pub fn type_foldable_derive(mut s: synstructure::Structure<'_>) -> proc_macro2::
     }
 
     s.add_bounds(synstructure::AddBounds::Generics);
-    let body_visit = s.each(|bind| {
-        quote! {
-            ::rustc_middle::ty::fold::TypeFoldable::visit_with(#bind, __folder)?;
-        }
-    });
     s.bind_with(|_| synstructure::BindStyle::Move);
     let body_fold = s.each_variant(|vi| {
         let bindings = vi.bindings();
@@ -36,14 +31,6 @@ pub fn type_foldable_derive(mut s: synstructure::Structure<'_>) -> proc_macro2::
             ) -> Result<Self, __F::Error> {
                 Ok(match self { #body_fold })
             }
-
-            fn visit_with<__F: ::rustc_middle::ty::fold::TypeVisitor<'tcx>>(
-                &self,
-                __folder: &mut __F
-            ) -> ::std::ops::ControlFlow<__F::BreakTy> {
-                match *self { #body_visit }
-                ::std::ops::ControlFlow::CONTINUE
-            }
         },
     )
 }

compiler/rustc_macros/src/type_visitable.rs

@@ -0,0 +1,33 @@
+use quote::quote;
+use syn::parse_quote;
+
+pub fn type_visitable_derive(mut s: synstructure::Structure<'_>) -> proc_macro2::TokenStream {
+    if let syn::Data::Union(_) = s.ast().data {
+        panic!("cannot derive on union")
+    }
+
+    if !s.ast().generics.lifetimes().any(|lt| lt.lifetime.ident == "tcx") {
+        s.add_impl_generic(parse_quote! { 'tcx });
+    }
+
+    s.add_bounds(synstructure::AddBounds::Generics);
+    let body_visit = s.each(|bind| {
+        quote! {
+            ::rustc_middle::ty::visit::TypeVisitable::visit_with(#bind, __visitor)?;
+        }
+    });
+    s.bind_with(|_| synstructure::BindStyle::Move);
+
+    s.bound_impl(
+        quote!(::rustc_middle::ty::visit::TypeVisitable<'tcx>),
+        quote! {
+            fn visit_with<__V: ::rustc_middle::ty::visit::TypeVisitor<'tcx>>(
+                &self,
+                __visitor: &mut __V
+            ) -> ::std::ops::ControlFlow<__V::BreakTy> {
+                match *self { #body_visit }
+                ::std::ops::ControlFlow::CONTINUE
+            }
+        },
+    )
+}

compiler/rustc_middle/src/hir/place.rs

@@ -4,18 +4,8 @@ use crate::ty::Ty;
 use rustc_hir::HirId;
 use rustc_target::abi::VariantIdx;
 
-#[derive(
-    Clone,
-    Copy,
-    Debug,
-    PartialEq,
-    Eq,
-    Hash,
-    TyEncodable,
-    TyDecodable,
-    TypeFoldable,
-    HashStable
-)]
+#[derive(Clone, Copy, Debug, PartialEq, Eq, Hash, TyEncodable, TyDecodable, HashStable)]
+#[derive(TypeFoldable, TypeVisitable)]
 pub enum PlaceBase {
     /// A temporary variable.
     Rvalue,
@@ -27,18 +17,8 @@ pub enum PlaceBase {
     Upvar(ty::UpvarId),
 }
 
-#[derive(
-    Clone,
-    Copy,
-    Debug,
-    PartialEq,
-    Eq,
-    Hash,
-    TyEncodable,
-    TyDecodable,
-    TypeFoldable,
-    HashStable
-)]
+#[derive(Clone, Copy, Debug, PartialEq, Eq, Hash, TyEncodable, TyDecodable, HashStable)]
+#[derive(TypeFoldable, TypeVisitable)]
 pub enum ProjectionKind {
     /// A dereference of a pointer, reference or `Box<T>` of the given type.
     Deref,
@@ -58,18 +38,8 @@ pub enum ProjectionKind {
     Subslice,
 }
 
-#[derive(
-    Clone,
-    Copy,
-    Debug,
-    PartialEq,
-    Eq,
-    Hash,
-    TyEncodable,
-    TyDecodable,
-    TypeFoldable,
-    HashStable
-)]
+#[derive(Clone, Copy, Debug, PartialEq, Eq, Hash, TyEncodable, TyDecodable, HashStable)]
+#[derive(TypeFoldable, TypeVisitable)]
 pub struct Projection<'tcx> {
     /// Type after the projection is applied.
     pub ty: Ty<'tcx>,
@@ -81,7 +51,8 @@ pub struct Projection<'tcx> {
 /// A `Place` represents how a value is located in memory.
 ///
 /// This is an HIR version of [`rustc_middle::mir::Place`].
-#[derive(Clone, Debug, PartialEq, Eq, Hash, TyEncodable, TyDecodable, TypeFoldable, HashStable)]
+#[derive(Clone, Debug, PartialEq, Eq, Hash, TyEncodable, TyDecodable, HashStable)]
+#[derive(TypeFoldable, TypeVisitable)]
 pub struct Place<'tcx> {
     /// The type of the `PlaceBase`
     pub base_ty: Ty<'tcx>,
@@ -94,7 +65,8 @@ pub struct Place<'tcx> {
 /// A `PlaceWithHirId` represents how a value is located in memory.
 ///
 /// This is an HIR version of [`rustc_middle::mir::Place`].
-#[derive(Clone, Debug, PartialEq, Eq, Hash, TyEncodable, TyDecodable, TypeFoldable, HashStable)]
+#[derive(Clone, Debug, PartialEq, Eq, Hash, TyEncodable, TyDecodable, HashStable)]
+#[derive(TypeFoldable, TypeVisitable)]
 pub struct PlaceWithHirId<'tcx> {
     /// `HirId` of the expression or pattern producing this value.
     pub hir_id: HirId,

compiler/rustc_middle/src/infer/canonical.rs

@@ -34,7 +34,7 @@ use std::ops::Index;
 /// variables have been rewritten to "canonical vars". These are
 /// numbered starting from 0 in order of first appearance.
 #[derive(Copy, Clone, Debug, PartialEq, Eq, Hash, TyDecodable, TyEncodable)]
-#[derive(HashStable, TypeFoldable, Lift)]
+#[derive(HashStable, TypeFoldable, TypeVisitable, Lift)]
 pub struct Canonical<'tcx, V> {
     pub max_universe: ty::UniverseIndex,
     pub variables: CanonicalVarInfos<'tcx>,
@@ -53,7 +53,7 @@ pub type CanonicalVarInfos<'tcx> = &'tcx List<CanonicalVarInfo<'tcx>>;
 /// variables. You will need to supply it later to instantiate the
 /// canonicalized query response.
 #[derive(Clone, Debug, PartialEq, Eq, Hash, TyDecodable, TyEncodable)]
-#[derive(HashStable, TypeFoldable, Lift)]
+#[derive(HashStable, TypeFoldable, TypeVisitable, Lift)]
 pub struct CanonicalVarValues<'tcx> {
     pub var_values: IndexVec<BoundVar, GenericArg<'tcx>>,
 }
@@ -173,7 +173,7 @@ pub enum CanonicalTyVarKind {
 /// After we execute a query with a canonicalized key, we get back a
 /// `Canonical<QueryResponse<..>>`. You can use
 /// `instantiate_query_result` to access the data in this result.
-#[derive(Clone, Debug, HashStable, TypeFoldable, Lift)]
+#[derive(Clone, Debug, HashStable, TypeFoldable, TypeVisitable, Lift)]
 pub struct QueryResponse<'tcx, R> {
     pub var_values: CanonicalVarValues<'tcx>,
     pub region_constraints: QueryRegionConstraints<'tcx>,
@@ -187,7 +187,7 @@ pub struct QueryResponse<'tcx, R> {
     pub value: R,
 }
 
-#[derive(Clone, Debug, Default, HashStable, TypeFoldable, Lift)]
+#[derive(Clone, Debug, Default, HashStable, TypeFoldable, TypeVisitable, Lift)]
 pub struct QueryRegionConstraints<'tcx> {
     pub outlives: Vec<QueryOutlivesConstraint<'tcx>>,
     pub member_constraints: Vec<MemberConstraint<'tcx>>,

compiler/rustc_middle/src/infer/mod.rs

@@ -13,7 +13,7 @@ use rustc_span::Span;
 /// ```text
 /// R0 member of [O1..On]
 /// ```
-#[derive(Debug, Clone, HashStable, TypeFoldable, Lift)]
+#[derive(Debug, Clone, HashStable, TypeFoldable, TypeVisitable, Lift)]
 pub struct MemberConstraint<'tcx> {
     /// The `DefId` of the opaque type causing this constraint: used for error reporting.
     pub opaque_type_def_id: DefId,

compiler/rustc_middle/src/mir/coverage.rs

@@ -100,7 +100,7 @@ impl From<InjectedExpressionId> for ExpressionOperandId {
     }
 }
 
-#[derive(Clone, PartialEq, TyEncodable, TyDecodable, Hash, HashStable, TypeFoldable)]
+#[derive(Clone, PartialEq, TyEncodable, TyDecodable, Hash, HashStable, TypeFoldable, TypeVisitable)]
 pub enum CoverageKind {
     Counter {
         function_source_hash: u64,
@@ -148,18 +148,8 @@ impl Debug for CoverageKind {
     }
 }
 
-#[derive(
-    Clone,
-    TyEncodable,
-    TyDecodable,
-    Hash,
-    HashStable,
-    TypeFoldable,
-    PartialEq,
-    Eq,
-    PartialOrd,
-    Ord
-)]
+#[derive(Clone, TyEncodable, TyDecodable, Hash, HashStable, PartialEq, Eq, PartialOrd, Ord)]
+#[derive(TypeFoldable, TypeVisitable)]
 pub struct CodeRegion {
     pub file_name: Symbol,
     pub start_line: u32,
@@ -178,7 +168,8 @@ impl Debug for CodeRegion {
     }
 }
 
-#[derive(Copy, Clone, Debug, PartialEq, TyEncodable, TyDecodable, Hash, HashStable, TypeFoldable)]
+#[derive(Copy, Clone, Debug, PartialEq, TyEncodable, TyDecodable, Hash, HashStable)]
+#[derive(TypeFoldable, TypeVisitable)]
 pub enum Op {
     Subtract,
     Add,

compiler/rustc_middle/src/mir/mod.rs

@@ -136,7 +136,7 @@ impl MirPhase {
 
 /// Where a specific `mir::Body` comes from.
 #[derive(Copy, Clone, Debug, PartialEq, Eq)]
-#[derive(HashStable, TyEncodable, TyDecodable, TypeFoldable)]
+#[derive(HashStable, TyEncodable, TyDecodable, TypeFoldable, TypeVisitable)]
 pub struct MirSource<'tcx> {
     pub instance: InstanceDef<'tcx>,
 
@@ -166,7 +166,7 @@ impl<'tcx> MirSource<'tcx> {
     }
 }
 
-#[derive(Clone, TyEncodable, TyDecodable, Debug, HashStable, TypeFoldable)]
+#[derive(Clone, TyEncodable, TyDecodable, Debug, HashStable, TypeFoldable, TypeVisitable)]
 pub struct GeneratorInfo<'tcx> {
     /// The yield type of the function, if it is a generator.
     pub yield_ty: Option<Ty<'tcx>>,
@@ -183,7 +183,7 @@ pub struct GeneratorInfo<'tcx> {
 }
 
 /// The lowered representation of a single function.
-#[derive(Clone, TyEncodable, TyDecodable, Debug, HashStable, TypeFoldable)]
+#[derive(Clone, TyEncodable, TyDecodable, Debug, HashStable, TypeFoldable, TypeVisitable)]
 pub struct Body<'tcx> {
     /// A list of basic blocks. References to basic block use a newtyped index type [`BasicBlock`]
     /// that indexes into this vector.
@@ -601,7 +601,7 @@ impl<'tcx> IndexMut<BasicBlock> for Body<'tcx> {
     }
 }
 
-#[derive(Copy, Clone, Debug, HashStable, TypeFoldable)]
+#[derive(Copy, Clone, Debug, HashStable, TypeFoldable, TypeVisitable)]
 pub enum ClearCrossCrate<T> {
     Clear,
     Set(T),
@@ -807,7 +807,7 @@ pub struct BlockTailInfo {
 ///
 /// This can be a binding declared by the user, a temporary inserted by the compiler, a function
 /// argument, or the return place.
-#[derive(Clone, Debug, TyEncodable, TyDecodable, HashStable, TypeFoldable)]
+#[derive(Clone, Debug, TyEncodable, TyDecodable, HashStable, TypeFoldable, TypeVisitable)]
 pub struct LocalDecl<'tcx> {
     /// Whether this is a mutable binding (i.e., `let x` or `let mut x`).
     ///
@@ -942,7 +942,7 @@ static_assert_size!(LocalDecl<'_>, 56);
 ///
 /// Not used for non-StaticRef temporaries, the return place, or anonymous
 /// function parameters.
-#[derive(Clone, Debug, TyEncodable, TyDecodable, HashStable, TypeFoldable)]
+#[derive(Clone, Debug, TyEncodable, TyDecodable, HashStable, TypeFoldable, TypeVisitable)]
 pub enum LocalInfo<'tcx> {
     /// A user-defined local variable or function parameter
     ///
@@ -1081,7 +1081,7 @@ impl<'tcx> LocalDecl<'tcx> {
     }
 }
 
-#[derive(Clone, TyEncodable, TyDecodable, HashStable, TypeFoldable)]
+#[derive(Clone, TyEncodable, TyDecodable, HashStable, TypeFoldable, TypeVisitable)]
 pub enum VarDebugInfoContents<'tcx> {
     /// NOTE(eddyb) There's an unenforced invariant that this `Place` is
     /// based on a `Local`, not a `Static`, and contains no indexing.
@@ -1099,7 +1099,7 @@ impl<'tcx> Debug for VarDebugInfoContents<'tcx> {
 }
 
 /// Debug information pertaining to a user variable.
-#[derive(Clone, Debug, TyEncodable, TyDecodable, HashStable, TypeFoldable)]
+#[derive(Clone, Debug, TyEncodable, TyDecodable, HashStable, TypeFoldable, TypeVisitable)]
 pub struct VarDebugInfo<'tcx> {
     pub name: Symbol,
 
@@ -1155,7 +1155,7 @@ impl BasicBlock {
 // BasicBlockData
 
 /// See [`BasicBlock`] for documentation on what basic blocks are at a high level.
-#[derive(Clone, Debug, TyEncodable, TyDecodable, HashStable, TypeFoldable)]
+#[derive(Clone, Debug, TyEncodable, TyDecodable, HashStable, TypeFoldable, TypeVisitable)]
 pub struct BasicBlockData<'tcx> {
     /// List of statements in this block.
     pub statements: Vec<Statement<'tcx>>,
@@ -1392,7 +1392,7 @@ impl<O: fmt::Debug> fmt::Debug for AssertKind<O> {
 ///////////////////////////////////////////////////////////////////////////
 // Statements
 
-#[derive(Clone, TyEncodable, TyDecodable, HashStable, TypeFoldable)]
+#[derive(Clone, TyEncodable, TyDecodable, HashStable, TypeFoldable, TypeVisitable)]
 pub struct Statement<'tcx> {
     pub source_info: SourceInfo,
     pub kind: StatementKind<'tcx>,
@@ -1758,7 +1758,7 @@ impl SourceScope {
     }
 }
 
-#[derive(Clone, Debug, TyEncodable, TyDecodable, HashStable, TypeFoldable)]
+#[derive(Clone, Debug, TyEncodable, TyDecodable, HashStable, TypeFoldable, TypeVisitable)]
 pub struct SourceScopeData<'tcx> {
     pub span: Span,
     pub parent_scope: Option<SourceScope>,
@@ -2524,7 +2524,7 @@ impl<'tcx> ConstantKind<'tcx> {
 /// The first will lead to the constraint `w: &'1 str` (for some
 /// inferred region `'1`). The second will lead to the constraint `w:
 /// &'static str`.
-#[derive(Clone, Debug, TyEncodable, TyDecodable, HashStable, TypeFoldable)]
+#[derive(Clone, Debug, TyEncodable, TyDecodable, HashStable, TypeFoldable, TypeVisitable)]
 pub struct UserTypeProjections {
     pub contents: Vec<(UserTypeProjection, Span)>,
 }

compiler/rustc_middle/src/mir/query.rs

@@ -161,7 +161,7 @@ rustc_index::newtype_index! {
 }
 
 /// The layout of generator state.
-#[derive(Clone, TyEncodable, TyDecodable, HashStable, TypeFoldable)]
+#[derive(Clone, TyEncodable, TyDecodable, HashStable, TypeFoldable, TypeVisitable)]
 pub struct GeneratorLayout<'tcx> {
     /// The type of every local stored inside the generator.
     pub field_tys: IndexVec<GeneratorSavedLocal, Ty<'tcx>>,

compiler/rustc_middle/src/mir/syntax.rs

@@ -179,7 +179,8 @@ pub enum BorrowKind {
 /// Not all of these are allowed at every [`MirPhase`]. Check the documentation there to see which
 /// ones you do not have to worry about. The MIR validator will generally enforce such restrictions,
 /// causing an ICE if they are violated.
-#[derive(Clone, Debug, PartialEq, TyEncodable, TyDecodable, Hash, HashStable, TypeFoldable)]
+#[derive(Clone, Debug, PartialEq, TyEncodable, TyDecodable, Hash, HashStable)]
+#[derive(TypeFoldable, TypeVisitable)]
 pub enum StatementKind<'tcx> {
     /// Assign statements roughly correspond to an assignment in Rust proper (`x = ...`) except
     /// without the possibility of dropping the previous value (that must be done separately, if at
@@ -376,13 +377,15 @@ pub enum FakeReadCause {
     ForIndex,
 }
 
-#[derive(Clone, Debug, PartialEq, TyEncodable, TyDecodable, Hash, HashStable, TypeFoldable)]
+#[derive(Clone, Debug, PartialEq, TyEncodable, TyDecodable, Hash, HashStable)]
+#[derive(TypeFoldable, TypeVisitable)]
 pub struct Coverage {
     pub kind: CoverageKind,
     pub code_region: Option<CodeRegion>,
 }
 
-#[derive(Clone, Debug, PartialEq, TyEncodable, TyDecodable, Hash, HashStable, TypeFoldable)]
+#[derive(Clone, Debug, PartialEq, TyEncodable, TyDecodable, Hash, HashStable)]
+#[derive(TypeFoldable, TypeVisitable)]
 pub struct CopyNonOverlapping<'tcx> {
     pub src: Operand<'tcx>,
     pub dst: Operand<'tcx>,
@@ -672,7 +675,8 @@ pub enum AssertKind<O> {
     ResumedAfterPanic(GeneratorKind),
 }
 
-#[derive(Clone, Debug, PartialEq, TyEncodable, TyDecodable, Hash, HashStable, TypeFoldable)]
+#[derive(Clone, Debug, PartialEq, TyEncodable, TyDecodable, Hash, HashStable)]
+#[derive(TypeFoldable, TypeVisitable)]
 pub enum InlineAsmOperand<'tcx> {
     In {
         reg: InlineAsmRegOrRegClass,

compiler/rustc_middle/src/mir/tcx.rs

@@ -9,7 +9,7 @@ use crate::ty::{self, Ty, TyCtxt};
 use rustc_hir as hir;
 use rustc_target::abi::VariantIdx;
 
-#[derive(Copy, Clone, Debug, TypeFoldable)]
+#[derive(Copy, Clone, Debug, TypeFoldable, TypeVisitable)]
 pub struct PlaceTy<'tcx> {
     pub ty: Ty<'tcx>,
     /// Downcast to a particular variant of an enum or a generator, if included.

compiler/rustc_middle/src/thir.rs

@@ -191,18 +191,8 @@ pub enum StmtKind<'tcx> {
 #[cfg(all(target_arch = "x86_64", target_pointer_width = "64"))]
 rustc_data_structures::static_assert_size!(Expr<'_>, 104);
 
-#[derive(
-    Clone,
-    Debug,
-    Copy,
-    PartialEq,
-    Eq,
-    Hash,
-    HashStable,
-    TyEncodable,
-    TyDecodable,
-    TypeFoldable
-)]
+#[derive(Clone, Debug, Copy, PartialEq, Eq, Hash, HashStable, TyEncodable, TyDecodable)]
+#[derive(TypeFoldable, TypeVisitable)]
 pub struct LocalVarId(pub hir::HirId);
 
 /// A THIR expression.

compiler/rustc_middle/src/traits/chalk.rs

@@ -390,7 +390,7 @@ impl<'tcx> chalk_ir::interner::HasInterner for RustInterner<'tcx> {
 }
 
 /// A chalk environment and goal.
-#[derive(Copy, Clone, PartialEq, Eq, Hash, Debug, HashStable, TypeFoldable)]
+#[derive(Copy, Clone, PartialEq, Eq, Hash, Debug, HashStable, TypeFoldable, TypeVisitable)]
 pub struct ChalkEnvironmentAndGoal<'tcx> {
     pub environment: &'tcx ty::List<ty::Predicate<'tcx>>,
     pub goal: ty::Predicate<'tcx>,

compiler/rustc_middle/src/traits/mod.rs

@@ -523,7 +523,7 @@ pub struct DerivedObligationCause<'tcx> {
     pub parent_code: InternedObligationCauseCode<'tcx>,
 }
 
-#[derive(Clone, Debug, TypeFoldable, Lift)]
+#[derive(Clone, Debug, TypeFoldable, TypeVisitable, Lift)]
 pub enum SelectionError<'tcx> {
     /// The trait is not implemented.
     Unimplemented,
@@ -592,7 +592,8 @@ pub type SelectionResult<'tcx, T> = Result<Option<T>, SelectionError<'tcx>>;
 /// ### The type parameter `N`
 ///
 /// See explanation on `ImplSourceUserDefinedData`.
-#[derive(Clone, PartialEq, Eq, TyEncodable, TyDecodable, HashStable, TypeFoldable, Lift)]
+#[derive(Clone, PartialEq, Eq, TyEncodable, TyDecodable, HashStable, Lift)]
+#[derive(TypeFoldable, TypeVisitable)]
 pub enum ImplSource<'tcx, N> {
     /// ImplSource identifying a particular impl.
     UserDefined(ImplSourceUserDefinedData<'tcx, N>),
@@ -753,14 +754,16 @@ impl<'tcx, N> ImplSource<'tcx, N> {
 /// is `Obligation`, as one might expect. During codegen, however, this
 /// is `()`, because codegen only requires a shallow resolution of an
 /// impl, and nested obligations are satisfied later.
-#[derive(Clone, PartialEq, Eq, TyEncodable, TyDecodable, HashStable, TypeFoldable, Lift)]
+#[derive(Clone, PartialEq, Eq, TyEncodable, TyDecodable, HashStable, Lift)]
+#[derive(TypeFoldable, TypeVisitable)]
 pub struct ImplSourceUserDefinedData<'tcx, N> {
     pub impl_def_id: DefId,
     pub substs: SubstsRef<'tcx>,
     pub nested: Vec<N>,
 }
 
-#[derive(Clone, PartialEq, Eq, TyEncodable, TyDecodable, HashStable, TypeFoldable, Lift)]
+#[derive(Clone, PartialEq, Eq, TyEncodable, TyDecodable, HashStable, Lift)]
+#[derive(TypeFoldable, TypeVisitable)]
 pub struct ImplSourceGeneratorData<'tcx, N> {
     pub generator_def_id: DefId,
     pub substs: SubstsRef<'tcx>,
@@ -769,7 +772,8 @@ pub struct ImplSourceGeneratorData<'tcx, N> {
     pub nested: Vec<N>,
 }
 
-#[derive(Clone, PartialEq, Eq, TyEncodable, TyDecodable, HashStable, TypeFoldable, Lift)]
+#[derive(Clone, PartialEq, Eq, TyEncodable, TyDecodable, HashStable, Lift)]
+#[derive(TypeFoldable, TypeVisitable)]
 pub struct ImplSourceClosureData<'tcx, N> {
     pub closure_def_id: DefId,
     pub substs: SubstsRef<'tcx>,
@@ -778,13 +782,15 @@ pub struct ImplSourceClosureData<'tcx, N> {
     pub nested: Vec<N>,
 }
 
-#[derive(Clone, PartialEq, Eq, TyEncodable, TyDecodable, HashStable, TypeFoldable, Lift)]
+#[derive(Clone, PartialEq, Eq, TyEncodable, TyDecodable, HashStable, Lift)]
+#[derive(TypeFoldable, TypeVisitable)]
 pub struct ImplSourceAutoImplData<N> {
     pub trait_def_id: DefId,
     pub nested: Vec<N>,
 }
 
-#[derive(Clone, PartialEq, Eq, TyEncodable, TyDecodable, HashStable, TypeFoldable, Lift)]
+#[derive(Clone, PartialEq, Eq, TyEncodable, TyDecodable, HashStable, Lift)]
+#[derive(TypeFoldable, TypeVisitable)]
 pub struct ImplSourceTraitUpcastingData<'tcx, N> {
     /// `Foo` upcast to the obligation trait. This will be some supertrait of `Foo`.
     pub upcast_trait_ref: ty::PolyTraitRef<'tcx>,
@@ -798,12 +804,14 @@ pub struct ImplSourceTraitUpcastingData<'tcx, N> {
     pub nested: Vec<N>,
 }
 
-#[derive(Clone, PartialEq, Eq, TyEncodable, TyDecodable, HashStable, TypeFoldable, Lift)]
+#[derive(Clone, PartialEq, Eq, TyEncodable, TyDecodable, HashStable, Lift)]
+#[derive(TypeFoldable, TypeVisitable)]
 pub struct ImplSourceBuiltinData<N> {
     pub nested: Vec<N>,
 }
 
-#[derive(PartialEq, Eq, Clone, TyEncodable, TyDecodable, HashStable, TypeFoldable, Lift)]
+#[derive(PartialEq, Eq, Clone, TyEncodable, TyDecodable, HashStable, Lift)]
+#[derive(TypeFoldable, TypeVisitable)]
 pub struct ImplSourceObjectData<'tcx, N> {
     /// `Foo` upcast to the obligation trait. This will be some supertrait of `Foo`.
     pub upcast_trait_ref: ty::PolyTraitRef<'tcx>,
@@ -817,7 +825,8 @@ pub struct ImplSourceObjectData<'tcx, N> {
     pub nested: Vec<N>,
 }
 
-#[derive(Clone, PartialEq, Eq, TyEncodable, TyDecodable, HashStable, TypeFoldable, Lift)]
+#[derive(Clone, PartialEq, Eq, TyEncodable, TyDecodable, HashStable, Lift)]
+#[derive(TypeFoldable, TypeVisitable)]
 pub struct ImplSourceFnPointerData<'tcx, N> {
     pub fn_ty: Ty<'tcx>,
     pub nested: Vec<N>,
@@ -830,12 +839,14 @@ pub struct ImplSourceDiscriminantKindData;
 #[derive(Clone, Debug, PartialEq, Eq, TyEncodable, TyDecodable, HashStable)]
 pub struct ImplSourcePointeeData;
 
-#[derive(Clone, PartialEq, Eq, TyEncodable, TyDecodable, HashStable, TypeFoldable, Lift)]
+#[derive(Clone, PartialEq, Eq, TyEncodable, TyDecodable, HashStable, Lift)]
+#[derive(TypeFoldable, TypeVisitable)]
 pub struct ImplSourceConstDestructData<N> {
     pub nested: Vec<N>,
 }
 
-#[derive(Clone, PartialEq, Eq, TyEncodable, TyDecodable, HashStable, TypeFoldable, Lift)]
+#[derive(Clone, PartialEq, Eq, TyEncodable, TyDecodable, HashStable, Lift)]
+#[derive(TypeFoldable, TypeVisitable)]
 pub struct ImplSourceTraitAliasData<'tcx, N> {
     pub alias_def_id: DefId,
     pub substs: SubstsRef<'tcx>,

compiler/rustc_middle/src/traits/query.rs

@@ -24,7 +24,8 @@ pub mod type_op {
     use rustc_hir::def_id::DefId;
     use std::fmt;
 
-    #[derive(Copy, Clone, Debug, Hash, PartialEq, Eq, HashStable, TypeFoldable, Lift)]
+    #[derive(Copy, Clone, Debug, Hash, PartialEq, Eq, HashStable, Lift)]
+    #[derive(TypeFoldable, TypeVisitable)]
     pub struct AscribeUserType<'tcx> {
         pub mir_ty: Ty<'tcx>,
         pub def_id: DefId,
@@ -37,19 +38,22 @@ pub mod type_op {
         }
     }
 
-    #[derive(Copy, Clone, Debug, Hash, PartialEq, Eq, HashStable, TypeFoldable, Lift)]
+    #[derive(Copy, Clone, Debug, Hash, PartialEq, Eq, HashStable, Lift)]
+    #[derive(TypeFoldable, TypeVisitable)]
     pub struct Eq<'tcx> {
         pub a: Ty<'tcx>,
         pub b: Ty<'tcx>,
     }
 
-    #[derive(Copy, Clone, Debug, Hash, PartialEq, Eq, HashStable, TypeFoldable, Lift)]
+    #[derive(Copy, Clone, Debug, Hash, PartialEq, Eq, HashStable, Lift)]
+    #[derive(TypeFoldable, TypeVisitable)]
     pub struct Subtype<'tcx> {
         pub sub: Ty<'tcx>,
         pub sup: Ty<'tcx>,
     }
 
-    #[derive(Copy, Clone, Debug, Hash, PartialEq, Eq, HashStable, TypeFoldable, Lift)]
+    #[derive(Copy, Clone, Debug, Hash, PartialEq, Eq, HashStable, Lift)]
+    #[derive(TypeFoldable, TypeVisitable)]
     pub struct ProvePredicate<'tcx> {
         pub predicate: Predicate<'tcx>,
     }
@@ -60,7 +64,8 @@ pub mod type_op {
         }
     }
 
-    #[derive(Copy, Clone, Debug, Hash, PartialEq, Eq, HashStable, TypeFoldable, Lift)]
+    #[derive(Copy, Clone, Debug, Hash, PartialEq, Eq, HashStable, Lift)]
+    #[derive(TypeFoldable, TypeVisitable)]
     pub struct Normalize<T> {
         pub value: T,
     }
@@ -107,7 +112,7 @@ impl<'tcx> From<TypeError<'tcx>> for NoSolution {
     }
 }
 
-#[derive(Clone, Debug, Default, HashStable, TypeFoldable, Lift)]
+#[derive(Clone, Debug, Default, HashStable, TypeFoldable, TypeVisitable, Lift)]
 pub struct DropckOutlivesResult<'tcx> {
     pub kinds: Vec<GenericArg<'tcx>>,
     pub overflows: Vec<Ty<'tcx>>,
@@ -208,7 +213,7 @@ pub struct MethodAutoderefBadTy<'tcx> {
 }
 
 /// Result from the `normalize_projection_ty` query.
-#[derive(Clone, Debug, HashStable, TypeFoldable, Lift)]
+#[derive(Clone, Debug, HashStable, TypeFoldable, TypeVisitable, Lift)]
 pub struct NormalizationResult<'tcx> {
     /// Result of normalization.
     pub normalized_ty: Ty<'tcx>,
@@ -221,7 +226,7 @@ pub struct NormalizationResult<'tcx> {
 /// case they are called implied bounds). They are fed to the
 /// `OutlivesEnv` which in turn is supplied to the region checker and
 /// other parts of the inference system.
-#[derive(Clone, Debug, TypeFoldable, Lift)]
+#[derive(Clone, Debug, TypeFoldable, TypeVisitable, Lift)]
 pub enum OutlivesBound<'tcx> {
     RegionSubRegion(ty::Region<'tcx>, ty::Region<'tcx>),
     RegionSubParam(ty::Region<'tcx>, ty::ParamTy),

compiler/rustc_middle/src/traits/select.rs

@@ -103,7 +103,7 @@ pub type EvaluationCache<'tcx> = Cache<
 /// required for associated types to work in default impls, as the bounds
 /// are visible both as projection bounds and as where-clauses from the
 /// parameter environment.
-#[derive(PartialEq, Eq, Debug, Clone, TypeFoldable)]
+#[derive(PartialEq, Eq, Debug, Clone, TypeFoldable, TypeVisitable)]
 pub enum SelectionCandidate<'tcx> {
     BuiltinCandidate {
         /// `false` if there are no *further* obligations.

compiler/rustc_middle/src/ty/adjustment.rs

@@ -77,7 +77,7 @@ pub enum PointerCast {
 ///    At some point, of course, `Box` should move out of the compiler, in which
 ///    case this is analogous to transforming a struct. E.g., `Box<[i32; 4]>` ->
 ///    `Box<[i32]>` is an `Adjust::Unsize` with the target `Box<[i32]>`.
-#[derive(Clone, TyEncodable, TyDecodable, HashStable, TypeFoldable)]
+#[derive(Clone, TyEncodable, TyDecodable, HashStable, TypeFoldable, TypeVisitable)]
 pub struct Adjustment<'tcx> {
     pub kind: Adjust<'tcx>,
     pub target: Ty<'tcx>,
@@ -89,7 +89,7 @@ impl<'tcx> Adjustment<'tcx> {
     }
 }
 
-#[derive(Clone, Debug, TyEncodable, TyDecodable, HashStable, TypeFoldable)]
+#[derive(Clone, Debug, TyEncodable, TyDecodable, HashStable, TypeFoldable, TypeVisitable)]
 pub enum Adjust<'tcx> {
     /// Go from ! to any type.
     NeverToAny,
@@ -107,7 +107,8 @@ pub enum Adjust<'tcx> {
 /// call, with the signature `&'a T -> &'a U` or `&'a mut T -> &'a mut U`.
 /// The target type is `U` in both cases, with the region and mutability
 /// being those shared by both the receiver and the returned reference.
-#[derive(Copy, Clone, PartialEq, Debug, TyEncodable, TyDecodable, HashStable, TypeFoldable)]
+#[derive(Copy, Clone, PartialEq, Debug, TyEncodable, TyDecodable, HashStable)]
+#[derive(TypeFoldable, TypeVisitable)]
 pub struct OverloadedDeref<'tcx> {
     pub region: ty::Region<'tcx>,
     pub mutbl: hir::Mutability,
@@ -165,7 +166,8 @@ impl From<AutoBorrowMutability> for hir::Mutability {
     }
 }
 
-#[derive(Copy, Clone, PartialEq, Debug, TyEncodable, TyDecodable, HashStable, TypeFoldable)]
+#[derive(Copy, Clone, PartialEq, Debug, TyEncodable, TyDecodable, HashStable)]
+#[derive(TypeFoldable, TypeVisitable)]
 pub enum AutoBorrow<'tcx> {
     /// Converts from T to &T.
     Ref(ty::Region<'tcx>, AutoBorrowMutability),

compiler/rustc_middle/src/ty/closure.rs

@@ -18,18 +18,8 @@ use self::BorrowKind::*;
 // This represents accessing self in the closure structure
 pub const CAPTURE_STRUCT_LOCAL: mir::Local = mir::Local::from_u32(1);
 
-#[derive(
-    Clone,
-    Copy,
-    Debug,
-    PartialEq,
-    Eq,
-    Hash,
-    TyEncodable,
-    TyDecodable,
-    TypeFoldable,
-    HashStable
-)]
+#[derive(Clone, Copy, Debug, PartialEq, Eq, Hash, TyEncodable, TyDecodable, HashStable)]
+#[derive(TypeFoldable, TypeVisitable)]
 pub struct UpvarPath {
     pub hir_id: hir::HirId,
 }
@@ -37,7 +27,8 @@ pub struct UpvarPath {
 /// Upvars do not get their own `NodeId`. Instead, we use the pair of
 /// the original var ID (that is, the root variable that is referenced
 /// by the upvar) and the ID of the closure expression.
-#[derive(Clone, Copy, PartialEq, Eq, Hash, TyEncodable, TyDecodable, TypeFoldable, HashStable)]
+#[derive(Clone, Copy, PartialEq, Eq, Hash, TyEncodable, TyDecodable, HashStable)]
+#[derive(TypeFoldable, TypeVisitable)]
 pub struct UpvarId {
     pub var_path: UpvarPath,
     pub closure_expr_id: LocalDefId,
@@ -51,7 +42,8 @@ impl UpvarId {
 
 /// Information describing the capture of an upvar. This is computed
 /// during `typeck`, specifically by `regionck`.
-#[derive(PartialEq, Clone, Debug, Copy, TyEncodable, TyDecodable, TypeFoldable, HashStable)]
+#[derive(PartialEq, Clone, Debug, Copy, TyEncodable, TyDecodable, HashStable)]
+#[derive(TypeFoldable, TypeVisitable)]
 pub enum UpvarCapture {
     /// Upvar is captured by value. This is always true when the
     /// closure is labeled `move`, but can also be true in other cases
@@ -139,7 +131,8 @@ impl<'tcx> ClosureKind {
 }
 
 /// A composite describing a `Place` that is captured by a closure.
-#[derive(PartialEq, Clone, Debug, TyEncodable, TyDecodable, TypeFoldable, HashStable)]
+#[derive(PartialEq, Clone, Debug, TyEncodable, TyDecodable, HashStable)]
+#[derive(TypeFoldable, TypeVisitable)]
 pub struct CapturedPlace<'tcx> {
     /// The `Place` that is captured.
     pub place: HirPlace<'tcx>,
@@ -284,7 +277,8 @@ pub fn is_ancestor_or_same_capture(
 /// Part of `MinCaptureInformationMap`; describes the capture kind (&, &mut, move)
 /// for a particular capture as well as identifying the part of the source code
 /// that triggered this capture to occur.
-#[derive(PartialEq, Clone, Debug, Copy, TyEncodable, TyDecodable, TypeFoldable, HashStable)]
+#[derive(PartialEq, Clone, Debug, Copy, TyEncodable, TyDecodable, HashStable)]
+#[derive(TypeFoldable, TypeVisitable)]
 pub struct CaptureInfo {
     /// Expr Id pointing to use that resulted in selecting the current capture kind
     ///
@@ -362,7 +356,8 @@ pub fn place_to_string_for_capture<'tcx>(tcx: TyCtxt<'tcx>, place: &HirPlace<'tc
     curr_string
 }
 
-#[derive(Clone, PartialEq, Debug, TyEncodable, TyDecodable, TypeFoldable, Copy, HashStable)]
+#[derive(Clone, PartialEq, Debug, TyEncodable, TyDecodable, Copy, HashStable)]
+#[derive(TypeFoldable, TypeVisitable)]
 pub enum BorrowKind {
     /// Data must be immutable and is aliasable.
     ImmBorrow,

compiler/rustc_middle/src/ty/context.rs

@@ -390,7 +390,7 @@ impl<'a, V> LocalTableInContextMut<'a, V> {
 /// Here, we would store the type `T`, the span of the value `x`, the "scope-span" for
 /// the scope that contains `x`, the expr `T` evaluated from, and the span of `foo.await`.
 #[derive(TyEncodable, TyDecodable, Clone, Debug, Eq, Hash, PartialEq, HashStable)]
-#[derive(TypeFoldable)]
+#[derive(TypeFoldable, TypeVisitable)]
 pub struct GeneratorInteriorTypeCause<'tcx> {
     /// Type of the captured binding.
     pub ty: Ty<'tcx>,
@@ -871,7 +871,7 @@ rustc_index::newtype_index! {
 pub type CanonicalUserTypeAnnotations<'tcx> =
     IndexVec<UserTypeAnnotationIndex, CanonicalUserTypeAnnotation<'tcx>>;
 
-#[derive(Clone, Debug, TyEncodable, TyDecodable, HashStable, TypeFoldable, Lift)]
+#[derive(Clone, Debug, TyEncodable, TyDecodable, HashStable, TypeFoldable, TypeVisitable, Lift)]
 pub struct CanonicalUserTypeAnnotation<'tcx> {
     pub user_ty: CanonicalUserType<'tcx>,
     pub span: Span,
@@ -931,7 +931,7 @@ impl<'tcx> CanonicalUserType<'tcx> {
 /// from constants that are named via paths, like `Foo::<A>::new` and
 /// so forth.
 #[derive(Copy, Clone, Debug, PartialEq, TyEncodable, TyDecodable)]
-#[derive(HashStable, TypeFoldable, Lift)]
+#[derive(HashStable, TypeFoldable, TypeVisitable, Lift)]
 pub enum UserType<'tcx> {
     Ty(Ty<'tcx>),
 

compiler/rustc_middle/src/ty/error.rs

@@ -13,7 +13,7 @@ use rustc_target::spec::abi;
 use std::borrow::Cow;
 use std::fmt;
 
-#[derive(Clone, Copy, Debug, PartialEq, Eq, TypeFoldable)]
+#[derive(Clone, Copy, Debug, PartialEq, Eq, TypeFoldable, TypeVisitable)]
 pub struct ExpectedFound<T> {
     pub expected: T,
     pub found: T,
@@ -30,7 +30,7 @@ impl<T> ExpectedFound<T> {
 }
 
 // Data structures used in type unification
-#[derive(Clone, Debug, TypeFoldable)]
+#[derive(Clone, Debug, TypeFoldable, TypeVisitable)]
 pub enum TypeError<'tcx> {
     Mismatch,
     ConstnessMismatch(ExpectedFound<ty::BoundConstness>),

compiler/rustc_middle/src/ty/instance.rs

@@ -25,7 +25,7 @@ pub struct Instance<'tcx> {
 }
 
 #[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash, Debug)]
-#[derive(TyEncodable, TyDecodable, HashStable, TypeFoldable)]
+#[derive(TyEncodable, TyDecodable, HashStable, TypeFoldable, TypeVisitable)]
 pub enum InstanceDef<'tcx> {
     /// A user-defined callable item.
     ///

compiler/rustc_middle/src/ty/mod.rs

@@ -206,7 +206,7 @@ impl MainDefinition {
 /// The "header" of an impl is everything outside the body: a Self type, a trait
 /// ref (in the case of a trait impl), and a set of predicates (from the
 /// bounds / where-clauses).
-#[derive(Clone, Debug, TypeFoldable)]
+#[derive(Clone, Debug, TypeFoldable, TypeVisitable)]
 pub struct ImplHeader<'tcx> {
     pub impl_def_id: DefId,
     pub self_ty: Ty<'tcx>,
@@ -214,24 +214,14 @@ pub struct ImplHeader<'tcx> {
     pub predicates: Vec<Predicate<'tcx>>,
 }
 
-#[derive(Copy, Clone, Debug, TypeFoldable)]
+#[derive(Copy, Clone, Debug, TypeFoldable, TypeVisitable)]
 pub enum ImplSubject<'tcx> {
     Trait(TraitRef<'tcx>),
     Inherent(Ty<'tcx>),
 }
 
-#[derive(
-    Copy,
-    Clone,
-    PartialEq,
-    Eq,
-    Hash,
-    TyEncodable,
-    TyDecodable,
-    HashStable,
-    Debug,
-    TypeFoldable
-)]
+#[derive(Copy, Clone, PartialEq, Eq, Hash, TyEncodable, TyDecodable, HashStable, Debug)]
+#[derive(TypeFoldable, TypeVisitable)]
 pub enum ImplPolarity {
     /// `impl Trait for Type`
     Positive,
@@ -307,18 +297,8 @@ impl fmt::Display for BoundConstness {
     }
 }
 
-#[derive(
-    Clone,
-    Debug,
-    PartialEq,
-    Eq,
-    Copy,
-    Hash,
-    TyEncodable,
-    TyDecodable,
-    HashStable,
-    TypeFoldable
-)]
+#[derive(Clone, Debug, PartialEq, Eq, Copy, Hash, TyEncodable, TyDecodable, HashStable)]
+#[derive(TypeFoldable, TypeVisitable)]
 pub struct ClosureSizeProfileData<'tcx> {
     /// Tuple containing the types of closure captures before the feature `capture_disjoint_fields`
     pub before_feature_tys: Ty<'tcx>,
@@ -618,7 +598,7 @@ impl rustc_errors::IntoDiagnosticArg for Predicate<'_> {
 }
 
 #[derive(Clone, Copy, PartialEq, Eq, Hash, TyEncodable, TyDecodable)]
-#[derive(HashStable, TypeFoldable)]
+#[derive(HashStable, TypeFoldable, TypeVisitable)]
 pub enum PredicateKind<'tcx> {
     /// Corresponds to `where Foo: Bar<A, B, C>`. `Foo` here would be
     /// the `Self` type of the trait reference and `A`, `B`, and `C`
@@ -790,7 +770,7 @@ impl<'tcx> Predicate<'tcx> {
 }
 
 #[derive(Clone, Copy, PartialEq, Eq, Hash, TyEncodable, TyDecodable)]
-#[derive(HashStable, TypeFoldable)]
+#[derive(HashStable, TypeFoldable, TypeVisitable)]
 pub struct TraitPredicate<'tcx> {
     pub trait_ref: TraitRef<'tcx>,
 
@@ -869,7 +849,7 @@ impl<'tcx> PolyTraitPredicate<'tcx> {
 }
 
 #[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, Debug, TyEncodable, TyDecodable)]
-#[derive(HashStable, TypeFoldable)]
+#[derive(HashStable, TypeFoldable, TypeVisitable)]
 pub struct OutlivesPredicate<A, B>(pub A, pub B); // `A: B`
 pub type RegionOutlivesPredicate<'tcx> = OutlivesPredicate<ty::Region<'tcx>, ty::Region<'tcx>>;
 pub type TypeOutlivesPredicate<'tcx> = OutlivesPredicate<Ty<'tcx>, ty::Region<'tcx>>;
@@ -880,7 +860,7 @@ pub type PolyTypeOutlivesPredicate<'tcx> = ty::Binder<'tcx, TypeOutlivesPredicat
 /// whether the `a` type is the type that we should label as "expected" when
 /// presenting user diagnostics.
 #[derive(Clone, Copy, PartialEq, Eq, Hash, Debug, TyEncodable, TyDecodable)]
-#[derive(HashStable, TypeFoldable)]
+#[derive(HashStable, TypeFoldable, TypeVisitable)]
 pub struct SubtypePredicate<'tcx> {
     pub a_is_expected: bool,
     pub a: Ty<'tcx>,
@@ -890,7 +870,7 @@ pub type PolySubtypePredicate<'tcx> = ty::Binder<'tcx, SubtypePredicate<'tcx>>;
 
 /// Encodes that we have to coerce *from* the `a` type to the `b` type.
 #[derive(Clone, Copy, PartialEq, Eq, Hash, Debug, TyEncodable, TyDecodable)]
-#[derive(HashStable, TypeFoldable)]
+#[derive(HashStable, TypeFoldable, TypeVisitable)]
 pub struct CoercePredicate<'tcx> {
     pub a: Ty<'tcx>,
     pub b: Ty<'tcx>,
@@ -898,7 +878,7 @@ pub struct CoercePredicate<'tcx> {
 pub type PolyCoercePredicate<'tcx> = ty::Binder<'tcx, CoercePredicate<'tcx>>;
 
 #[derive(Debug, Copy, Clone, PartialEq, Eq, Hash, PartialOrd, Ord, TyEncodable, TyDecodable)]
-#[derive(HashStable, TypeFoldable)]
+#[derive(HashStable, TypeFoldable, TypeVisitable)]
 pub enum Term<'tcx> {
     Ty(Ty<'tcx>),
     Const(Const<'tcx>),
@@ -946,7 +926,7 @@ impl<'tcx> Term<'tcx> {
 /// Form #2 eventually yields one of these `ProjectionPredicate`
 /// instances to normalize the LHS.
 #[derive(Copy, Clone, PartialEq, Eq, Hash, TyEncodable, TyDecodable)]
-#[derive(HashStable, TypeFoldable)]
+#[derive(HashStable, TypeFoldable, TypeVisitable)]
 pub struct ProjectionPredicate<'tcx> {
     pub projection_ty: ProjectionTy<'tcx>,
     pub term: Term<'tcx>,
@@ -1090,7 +1070,7 @@ impl<'tcx> Predicate<'tcx> {
 /// `[[], [U:Bar<T>]]`. Now if there were some particular reference
 /// like `Foo<isize,usize>`, then the `InstantiatedPredicates` would be `[[],
 /// [usize:Bar<isize>]]`.
-#[derive(Clone, Debug, TypeFoldable)]
+#[derive(Clone, Debug, TypeFoldable, TypeVisitable)]
 pub struct InstantiatedPredicates<'tcx> {
     pub predicates: Vec<Predicate<'tcx>>,
     pub spans: Vec<Span>,
@@ -1106,24 +1086,14 @@ impl<'tcx> InstantiatedPredicates<'tcx> {
     }
 }
 
-#[derive(
-    Copy,
-    Clone,
-    Debug,
-    PartialEq,
-    Eq,
-    HashStable,
-    TyEncodable,
-    TyDecodable,
-    TypeFoldable,
-    Lift
-)]
+#[derive(Copy, Clone, Debug, PartialEq, Eq, HashStable, TyEncodable, TyDecodable, Lift)]
+#[derive(TypeFoldable, TypeVisitable)]
 pub struct OpaqueTypeKey<'tcx> {
     pub def_id: DefId,
     pub substs: SubstsRef<'tcx>,
 }
 
-#[derive(Copy, Clone, Debug, TypeFoldable, HashStable, TyEncodable, TyDecodable)]
+#[derive(Copy, Clone, Debug, TypeFoldable, TypeVisitable, HashStable, TyEncodable, TyDecodable)]
 pub struct OpaqueHiddenType<'tcx> {
     /// The span of this particular definition of the opaque type. So
     /// for example:
@@ -1259,7 +1229,7 @@ pub type PlaceholderConst<'tcx> = Placeholder<BoundConst<'tcx>>;
 /// except that instead of a `Ty` we bundle the `DefId` of the const parameter.
 /// Meaning that we need to use `type_of(const_param_did)` if `const_param_did` is `Some`
 /// to get the type of `did`.
-#[derive(Copy, Clone, Debug, TypeFoldable, Lift, TyEncodable, TyDecodable)]
+#[derive(Copy, Clone, Debug, TypeFoldable, TypeVisitable, Lift, TyEncodable, TyDecodable)]
 #[derive(PartialEq, Eq, PartialOrd, Ord)]
 #[derive(Hash, HashStable)]
 pub struct WithOptConstParam<T> {
@@ -1575,7 +1545,7 @@ impl<'tcx> PolyTraitRef<'tcx> {
     }
 }
 
-#[derive(Copy, Clone, Debug, PartialEq, Eq, Hash, TypeFoldable)]
+#[derive(Copy, Clone, Debug, PartialEq, Eq, Hash, TypeFoldable, TypeVisitable)]
 pub struct ParamEnvAnd<'tcx, T> {
     pub param_env: ParamEnv<'tcx>,
     pub value: T,

compiler/rustc_middle/src/ty/print/pretty.rs

@@ -2388,7 +2388,7 @@ macro_rules! define_print_and_forward_display {
 /// Wrapper type for `ty::TraitRef` which opts-in to pretty printing only
 /// the trait path. That is, it will print `Trait<U>` instead of
 /// `<T as Trait<U>>`.
-#[derive(Copy, Clone, TypeFoldable, Lift)]
+#[derive(Copy, Clone, TypeFoldable, TypeVisitable, Lift)]
 pub struct TraitRefPrintOnlyTraitPath<'tcx>(ty::TraitRef<'tcx>);
 
 impl<'tcx> fmt::Debug for TraitRefPrintOnlyTraitPath<'tcx> {
@@ -2400,7 +2400,7 @@ impl<'tcx> fmt::Debug for TraitRefPrintOnlyTraitPath<'tcx> {
 /// Wrapper type for `ty::TraitRef` which opts-in to pretty printing only
 /// the trait name. That is, it will print `Trait` instead of
 /// `<T as Trait<U>>`.
-#[derive(Copy, Clone, TypeFoldable, Lift)]
+#[derive(Copy, Clone, TypeFoldable, TypeVisitable, Lift)]
 pub struct TraitRefPrintOnlyTraitName<'tcx>(ty::TraitRef<'tcx>);
 
 impl<'tcx> fmt::Debug for TraitRefPrintOnlyTraitName<'tcx> {
@@ -2425,7 +2425,7 @@ impl<'tcx> ty::Binder<'tcx, ty::TraitRef<'tcx>> {
     }
 }
 
-#[derive(Copy, Clone, TypeFoldable, Lift)]
+#[derive(Copy, Clone, TypeFoldable, TypeVisitable, Lift)]
 pub struct TraitPredPrintModifiersAndPath<'tcx>(ty::TraitPredicate<'tcx>);
 
 impl<'tcx> fmt::Debug for TraitPredPrintModifiersAndPath<'tcx> {

compiler/rustc_middle/src/ty/relate.rs

@@ -345,7 +345,7 @@ impl<'tcx> Relate<'tcx> for ty::ExistentialTraitRef<'tcx> {
     }
 }
 
-#[derive(Copy, Debug, Clone, TypeFoldable)]
+#[derive(Copy, Debug, Clone, TypeFoldable, TypeVisitable)]
 struct GeneratorWitness<'tcx>(&'tcx ty::List<Ty<'tcx>>);
 
 impl<'tcx> Relate<'tcx> for GeneratorWitness<'tcx> {

compiler/rustc_middle/src/ty/sty.rs

@@ -38,7 +38,7 @@ pub type TyKind<'tcx> = IrTyKind<TyCtxt<'tcx>>;
 pub type RegionKind<'tcx> = IrRegionKind<TyCtxt<'tcx>>;
 
 #[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, Debug, TyEncodable, TyDecodable)]
-#[derive(HashStable, TypeFoldable, Lift)]
+#[derive(HashStable, TypeFoldable, TypeVisitable, Lift)]
 pub struct TypeAndMut<'tcx> {
     pub ty: Ty<'tcx>,
     pub mutbl: hir::Mutability,
@@ -201,7 +201,7 @@ static_assert_size!(TyKind<'_>, 32);
 /// * `GR`: The "return type", which is the type of value returned upon
 ///   completion of the generator.
 /// * `GW`: The "generator witness".
-#[derive(Copy, Clone, Debug, TypeFoldable)]
+#[derive(Copy, Clone, Debug, TypeFoldable, TypeVisitable)]
 pub struct ClosureSubsts<'tcx> {
     /// Lifetime and type parameters from the enclosing function,
     /// concatenated with a tuple containing the types of the upvars.
@@ -328,7 +328,7 @@ impl<'tcx> ClosureSubsts<'tcx> {
 }
 
 /// Similar to `ClosureSubsts`; see the above documentation for more.
-#[derive(Copy, Clone, Debug, TypeFoldable)]
+#[derive(Copy, Clone, Debug, TypeFoldable, TypeVisitable)]
 pub struct GeneratorSubsts<'tcx> {
     pub substs: SubstsRef<'tcx>,
 }
@@ -608,7 +608,7 @@ impl<'tcx> UpvarSubsts<'tcx> {
 /// type of the constant. The reason that `R` is represented as an extra type parameter
 /// is the same reason that [`ClosureSubsts`] have `CS` and `U` as type parameters:
 /// inline const can reference lifetimes that are internal to the creating function.
-#[derive(Copy, Clone, Debug, TypeFoldable)]
+#[derive(Copy, Clone, Debug, TypeFoldable, TypeVisitable)]
 pub struct InlineConstSubsts<'tcx> {
     /// Generic parameters from the enclosing item,
     /// concatenated with the inferred type of the constant.
@@ -655,7 +655,7 @@ impl<'tcx> InlineConstSubsts<'tcx> {
 }
 
 #[derive(Debug, Copy, Clone, PartialEq, PartialOrd, Ord, Eq, Hash, TyEncodable, TyDecodable)]
-#[derive(HashStable, TypeFoldable)]
+#[derive(HashStable, TypeFoldable, TypeVisitable)]
 pub enum ExistentialPredicate<'tcx> {
     /// E.g., `Iterator`.
     Trait(ExistentialTraitRef<'tcx>),
@@ -781,7 +781,7 @@ impl<'tcx> List<ty::Binder<'tcx, ExistentialPredicate<'tcx>>> {
 /// Trait references also appear in object types like `Foo<U>`, but in
 /// that case the `Self` parameter is absent from the substitutions.
 #[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash, TyEncodable, TyDecodable)]
-#[derive(HashStable, TypeFoldable)]
+#[derive(HashStable, TypeFoldable, TypeVisitable)]
 pub struct TraitRef<'tcx> {
     pub def_id: DefId,
     pub substs: SubstsRef<'tcx>,
@@ -853,7 +853,7 @@ impl<'tcx> PolyTraitRef<'tcx> {
 /// The substitutions don't include the erased `Self`, only trait
 /// type and lifetime parameters (`[X, Y]` and `['a, 'b]` above).
 #[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash, TyEncodable, TyDecodable)]
-#[derive(HashStable, TypeFoldable)]
+#[derive(HashStable, TypeFoldable, TypeVisitable)]
 pub struct ExistentialTraitRef<'tcx> {
     pub def_id: DefId,
     pub substs: SubstsRef<'tcx>,
@@ -1143,7 +1143,7 @@ impl<'tcx, T> Binder<'tcx, Option<T>> {
 /// Represents the projection of an associated type. In explicit UFCS
 /// form this would be written `<T as Trait<..>>::N`.
 #[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash, Debug, TyEncodable, TyDecodable)]
-#[derive(HashStable, TypeFoldable)]
+#[derive(HashStable, TypeFoldable, TypeVisitable)]
 pub struct ProjectionTy<'tcx> {
     /// The parameters of the associated item.
     pub substs: SubstsRef<'tcx>,
@@ -1192,7 +1192,7 @@ impl<'tcx> ProjectionTy<'tcx> {
     }
 }
 
-#[derive(Copy, Clone, Debug, TypeFoldable)]
+#[derive(Copy, Clone, Debug, TypeFoldable, TypeVisitable)]
 pub struct GenSig<'tcx> {
     pub resume_ty: Ty<'tcx>,
     pub yield_ty: Ty<'tcx>,
@@ -1208,7 +1208,7 @@ pub type PolyGenSig<'tcx> = Binder<'tcx, GenSig<'tcx>>;
 /// - `output`: is the return type.
 /// - `c_variadic`: indicates whether this is a C-variadic function.
 #[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash, TyEncodable, TyDecodable)]
-#[derive(HashStable, TypeFoldable)]
+#[derive(HashStable, TypeFoldable, TypeVisitable)]
 pub struct FnSig<'tcx> {
     pub inputs_and_output: &'tcx List<Ty<'tcx>>,
     pub c_variadic: bool,
@@ -1385,7 +1385,7 @@ impl From<BoundVar> for BoundTy {
 
 /// A `ProjectionPredicate` for an `ExistentialTraitRef`.
 #[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, Debug, TyEncodable, TyDecodable)]
-#[derive(HashStable, TypeFoldable)]
+#[derive(HashStable, TypeFoldable, TypeVisitable)]
 pub struct ExistentialProjection<'tcx> {
     pub item_def_id: DefId,
     pub substs: SubstsRef<'tcx>,

compiler/rustc_middle/src/ty/subst.rs

@@ -722,7 +722,7 @@ impl<'a, 'tcx> SubstFolder<'a, 'tcx> {
 /// Stores the user-given substs to reach some fully qualified path
 /// (e.g., `<T>::Item` or `<T as Trait>::Item`).
 #[derive(Copy, Clone, Debug, PartialEq, Eq, Hash, TyEncodable, TyDecodable)]
-#[derive(HashStable, TypeFoldable, Lift)]
+#[derive(HashStable, TypeFoldable, TypeVisitable, Lift)]
 pub struct UserSubsts<'tcx> {
     /// The substitutions for the item as given by the user.
     pub substs: SubstsRef<'tcx>,
@@ -749,7 +749,7 @@ pub struct UserSubsts<'tcx> {
 /// the self type, giving `Foo<?A>`. Finally, we unify that with
 /// the self type here, which contains `?A` to be `&'static u32`
 #[derive(Copy, Clone, Debug, PartialEq, Eq, Hash, TyEncodable, TyDecodable)]
-#[derive(HashStable, TypeFoldable, Lift)]
+#[derive(HashStable, TypeFoldable, TypeVisitable, Lift)]
 pub struct UserSelfTy<'tcx> {
     pub impl_def_id: DefId,
     pub self_ty: Ty<'tcx>,

compiler/rustc_trait_selection/src/traits/query/type_op/implied_outlives_bounds.rs

@@ -3,7 +3,7 @@ use crate::traits::query::Fallible;
 use rustc_infer::traits::query::OutlivesBound;
 use rustc_middle::ty::{self, ParamEnvAnd, Ty, TyCtxt};
 
-#[derive(Copy, Clone, Debug, HashStable, TypeFoldable, Lift)]
+#[derive(Copy, Clone, Debug, HashStable, TypeFoldable, TypeVisitable, Lift)]
 pub struct ImpliedOutlivesBounds<'tcx> {
     pub ty: Ty<'tcx>,
 }

compiler/rustc_trait_selection/src/traits/query/type_op/outlives.rs

@@ -3,7 +3,7 @@ use crate::traits::query::dropck_outlives::{trivial_dropck_outlives, DropckOutli
 use crate::traits::query::Fallible;
 use rustc_middle::ty::{ParamEnvAnd, Ty, TyCtxt};
 
-#[derive(Copy, Clone, Debug, HashStable, TypeFoldable, Lift)]
+#[derive(Copy, Clone, Debug, HashStable, TypeFoldable, TypeVisitable, Lift)]
 pub struct DropckOutlives<'tcx> {
     dropped_ty: Ty<'tcx>,
 }