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diff --git a/vendor/chalk-ir-0.87.0/src/visit.rs b/vendor/chalk-ir-0.87.0/src/visit.rs
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+++ b/vendor/chalk-ir-0.87.0/src/visit.rs
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+//! Traits for visiting bits of IR.
+use std::fmt::Debug;
+use std::ops::ControlFlow;
+
+use crate::{
+    BoundVar, Const, ConstValue, DebruijnIndex, DomainGoal, Goal, InferenceVar, Interner, Lifetime,
+    LifetimeData, PlaceholderIndex, ProgramClause, Ty, TyKind, WhereClause,
+};
+
+mod binder_impls;
+mod boring_impls;
+pub mod visitors;
+
+pub use visitors::VisitExt;
+
+/// Unwraps a `ControlFlow` or propagates its `Break` value.
+/// This replaces the `Try` implementation that would be used
+/// with `std::ops::ControlFlow`.
+#[macro_export]
+macro_rules! try_break {
+    ($expr:expr) => {
+        match $expr {
+            std::ops::ControlFlow::Continue(c) => c,
+            std::ops::ControlFlow::Break(b) => return std::ops::ControlFlow::Break(b),
+        }
+    };
+}
+
+/// A "visitor" recursively folds some term -- that is, some bit of IR,
+/// such as a `Goal`, and computes a value as a result.
+///
+///
+/// To **apply** a visitor, use the `TypeVisitable::visit_with` method, like so
+///
+/// ```rust,ignore
+/// let result = x.visit_with(&mut visitor, 0);
+/// ```
+pub trait TypeVisitor<I: Interner> {
+    /// The "break type" of the visitor, often `()`. It represents the result
+    /// the visitor yields when it stops visiting.
+    type BreakTy;
+
+    /// Creates a `dyn` value from this visitor. Unfortunately, this
+    /// must be added manually to each impl of visitor; it permits the
+    /// default implements below to create a `&mut dyn TypeVisitor` from
+    /// `Self` without knowing what `Self` is (by invoking this
+    /// method). Effectively, this limits impls of `visitor` to types
+    /// for which we are able to create a dyn value (i.e., not `[T]`
+    /// types).
+    fn as_dyn(&mut self) -> &mut dyn TypeVisitor<I, BreakTy = Self::BreakTy>;
+
+    /// Top-level callback: invoked for each `Ty<I>` that is
+    /// encountered when visiting. By default, invokes
+    /// `super_visit_with`, which will in turn invoke the more
+    /// specialized visiting methods below, like `visit_free_var`.
+    fn visit_ty(&mut self, ty: &Ty<I>, outer_binder: DebruijnIndex) -> ControlFlow<Self::BreakTy> {
+        ty.super_visit_with(self.as_dyn(), outer_binder)
+    }
+
+    /// Top-level callback: invoked for each `Lifetime<I>` that is
+    /// encountered when visiting. By default, invokes
+    /// `super_visit_with`, which will in turn invoke the more
+    /// specialized visiting methods below, like `visit_free_var`.
+    fn visit_lifetime(
+        &mut self,
+        lifetime: &Lifetime<I>,
+        outer_binder: DebruijnIndex,
+    ) -> ControlFlow<Self::BreakTy> {
+        lifetime.super_visit_with(self.as_dyn(), outer_binder)
+    }
+
+    /// Top-level callback: invoked for each `Const<I>` that is
+    /// encountered when visiting. By default, invokes
+    /// `super_visit_with`, which will in turn invoke the more
+    /// specialized visiting methods below, like `visit_free_var`.
+    fn visit_const(
+        &mut self,
+        constant: &Const<I>,
+        outer_binder: DebruijnIndex,
+    ) -> ControlFlow<Self::BreakTy> {
+        constant.super_visit_with(self.as_dyn(), outer_binder)
+    }
+
+    /// Invoked for every program clause. By default, recursively visits the goals contents.
+    fn visit_program_clause(
+        &mut self,
+        clause: &ProgramClause<I>,
+        outer_binder: DebruijnIndex,
+    ) -> ControlFlow<Self::BreakTy> {
+        clause.super_visit_with(self.as_dyn(), outer_binder)
+    }
+
+    /// Invoked for every goal. By default, recursively visits the goals contents.
+    fn visit_goal(
+        &mut self,
+        goal: &Goal<I>,
+        outer_binder: DebruijnIndex,
+    ) -> ControlFlow<Self::BreakTy> {
+        goal.super_visit_with(self.as_dyn(), outer_binder)
+    }
+
+    /// Invoked for each domain goal.
+    fn visit_domain_goal(
+        &mut self,
+        domain_goal: &DomainGoal<I>,
+        outer_binder: DebruijnIndex,
+    ) -> ControlFlow<Self::BreakTy> {
+        domain_goal.super_visit_with(self.as_dyn(), outer_binder)
+    }
+
+    /// If overridden to return true, then visiting will panic if a
+    /// free variable is encountered. This should be done if free
+    /// type/lifetime/const variables are not expected.
+    fn forbid_free_vars(&self) -> bool {
+        false
+    }
+
+    /// Invoked for `BoundVar` instances that are not bound
+    /// within the type being visited over:
+    fn visit_free_var(
+        &mut self,
+        bound_var: BoundVar,
+        outer_binder: DebruijnIndex,
+    ) -> ControlFlow<Self::BreakTy> {
+        if self.forbid_free_vars() {
+            panic!(
+                "unexpected free variable `{:?}` with outer binder {:?}",
+                bound_var, outer_binder
+            )
+        } else {
+            ControlFlow::Continue(())
+        }
+    }
+
+    /// If overridden to return true, we will panic when a free
+    /// placeholder type/lifetime is encountered.
+    fn forbid_free_placeholders(&self) -> bool {
+        false
+    }
+
+    /// Invoked for each occurrence of a placeholder type; these are
+    /// used when we instantiate binders universally.
+    fn visit_free_placeholder(
+        &mut self,
+        universe: PlaceholderIndex,
+        _outer_binder: DebruijnIndex,
+    ) -> ControlFlow<Self::BreakTy> {
+        if self.forbid_free_placeholders() {
+            panic!("unexpected placeholder type `{:?}`", universe)
+        } else {
+            ControlFlow::Continue(())
+        }
+    }
+
+    /// Invoked for each where clause.
+    fn visit_where_clause(
+        &mut self,
+        where_clause: &WhereClause<I>,
+        outer_binder: DebruijnIndex,
+    ) -> ControlFlow<Self::BreakTy> {
+        where_clause.super_visit_with(self.as_dyn(), outer_binder)
+    }
+
+    /// If overridden to return true, inference variables will trigger
+    /// panics when visited. Used when inference variables are
+    /// unexpected.
+    fn forbid_inference_vars(&self) -> bool {
+        false
+    }
+
+    /// Invoked for each occurrence of a inference type; these are
+    /// used when we instantiate binders universally.
+    fn visit_inference_var(
+        &mut self,
+        var: InferenceVar,
+        _outer_binder: DebruijnIndex,
+    ) -> ControlFlow<Self::BreakTy> {
+        if self.forbid_inference_vars() {
+            panic!("unexpected inference type `{:?}`", var)
+        } else {
+            ControlFlow::Continue(())
+        }
+    }
+
+    /// Gets the visitor's interner.
+    fn interner(&self) -> I;
+}
+
+/// Applies the given `visitor` to a value, producing a visited result
+/// of type `TypeVisitor::Result`.
+pub trait TypeVisitable<I: Interner>: Debug {
+    /// Apply the given visitor `visitor` to `self`; `binders` is the
+    /// number of binders that are in scope when beginning the
+    /// visitor. Typically `binders` starts as 0, but is adjusted when
+    /// we encounter `Binders<T>` in the IR or other similar
+    /// constructs.
+    fn visit_with<B>(
+        &self,
+        visitor: &mut dyn TypeVisitor<I, BreakTy = B>,
+        outer_binder: DebruijnIndex,
+    ) -> ControlFlow<B>;
+}
+
+/// For types where "visit" invokes a callback on the `visitor`, the
+/// `TypeSuperVisitable` trait captures the recursive behavior that visits all
+/// the contents of the type.
+pub trait TypeSuperVisitable<I: Interner>: TypeVisitable<I> {
+    /// Recursively visits the type contents.
+    fn super_visit_with<B>(
+        &self,
+        visitor: &mut dyn TypeVisitor<I, BreakTy = B>,
+        outer_binder: DebruijnIndex,
+    ) -> ControlFlow<B>;
+}
+
+/// "visiting" a type invokes the `visit_ty` method on the visitor; this
+/// usually (in turn) invokes `super_visit_ty` to visit the individual
+/// parts.
+impl<I: Interner> TypeVisitable<I> for Ty<I> {
+    fn visit_with<B>(
+        &self,
+        visitor: &mut dyn TypeVisitor<I, BreakTy = B>,
+        outer_binder: DebruijnIndex,
+    ) -> ControlFlow<B> {
+        visitor.visit_ty(self, outer_binder)
+    }
+}
+
+/// "Super visit" for a type invokes the more detailed callbacks on the type
+impl<I> TypeSuperVisitable<I> for Ty<I>
+where
+    I: Interner,
+{
+    fn super_visit_with<B>(
+        &self,
+        visitor: &mut dyn TypeVisitor<I, BreakTy = B>,
+        outer_binder: DebruijnIndex,
+    ) -> ControlFlow<B> {
+        let interner = visitor.interner();
+        match self.kind(interner) {
+            TyKind::BoundVar(bound_var) => {
+                if bound_var.shifted_out_to(outer_binder).is_some() {
+                    visitor.visit_free_var(*bound_var, outer_binder)
+                } else {
+                    ControlFlow::Continue(())
+                }
+            }
+            TyKind::Dyn(clauses) => clauses.visit_with(visitor, outer_binder),
+            TyKind::InferenceVar(var, _) => visitor.visit_inference_var(*var, outer_binder),
+            TyKind::Placeholder(ui) => visitor.visit_free_placeholder(*ui, outer_binder),
+            TyKind::Alias(proj) => proj.visit_with(visitor, outer_binder),
+            TyKind::Function(fun) => fun.visit_with(visitor, outer_binder),
+            TyKind::Adt(_id, substitution) => substitution.visit_with(visitor, outer_binder),
+            TyKind::AssociatedType(_assoc_ty, substitution) => {
+                substitution.visit_with(visitor, outer_binder)
+            }
+            TyKind::Scalar(scalar) => scalar.visit_with(visitor, outer_binder),
+            TyKind::Str => ControlFlow::Continue(()),
+            TyKind::Tuple(arity, substitution) => {
+                try_break!(arity.visit_with(visitor, outer_binder));
+                substitution.visit_with(visitor, outer_binder)
+            }
+            TyKind::OpaqueType(opaque_ty, substitution) => {
+                try_break!(opaque_ty.visit_with(visitor, outer_binder));
+                substitution.visit_with(visitor, outer_binder)
+            }
+            TyKind::Slice(substitution) => substitution.visit_with(visitor, outer_binder),
+            TyKind::FnDef(fn_def, substitution) => {
+                try_break!(fn_def.visit_with(visitor, outer_binder));
+                substitution.visit_with(visitor, outer_binder)
+            }
+            TyKind::Ref(mutability, lifetime, ty) => {
+                try_break!(mutability.visit_with(visitor, outer_binder));
+                try_break!(lifetime.visit_with(visitor, outer_binder));
+                ty.visit_with(visitor, outer_binder)
+            }
+            TyKind::Raw(mutability, ty) => {
+                try_break!(mutability.visit_with(visitor, outer_binder));
+                ty.visit_with(visitor, outer_binder)
+            }
+            TyKind::Never => ControlFlow::Continue(()),
+            TyKind::Array(ty, const_) => {
+                try_break!(ty.visit_with(visitor, outer_binder));
+                const_.visit_with(visitor, outer_binder)
+            }
+            TyKind::Closure(id, substitution) => {
+                try_break!(id.visit_with(visitor, outer_binder));
+                substitution.visit_with(visitor, outer_binder)
+            }
+            TyKind::Generator(generator, substitution) => {
+                try_break!(generator.visit_with(visitor, outer_binder));
+                substitution.visit_with(visitor, outer_binder)
+            }
+            TyKind::GeneratorWitness(witness, substitution) => {
+                try_break!(witness.visit_with(visitor, outer_binder));
+                substitution.visit_with(visitor, outer_binder)
+            }
+            TyKind::Foreign(foreign_ty) => foreign_ty.visit_with(visitor, outer_binder),
+            TyKind::Error => ControlFlow::Continue(()),
+        }
+    }
+}
+
+impl<I: Interner> TypeVisitable<I> for Lifetime<I> {
+    fn visit_with<B>(
+        &self,
+        visitor: &mut dyn TypeVisitor<I, BreakTy = B>,
+        outer_binder: DebruijnIndex,
+    ) -> ControlFlow<B> {
+        visitor.visit_lifetime(self, outer_binder)
+    }
+}
+
+impl<I: Interner> TypeSuperVisitable<I> for Lifetime<I> {
+    fn super_visit_with<B>(
+        &self,
+        visitor: &mut dyn TypeVisitor<I, BreakTy = B>,
+        outer_binder: DebruijnIndex,
+    ) -> ControlFlow<B> {
+        let interner = visitor.interner();
+        match self.data(interner) {
+            LifetimeData::BoundVar(bound_var) => {
+                if bound_var.shifted_out_to(outer_binder).is_some() {
+                    visitor.visit_free_var(*bound_var, outer_binder)
+                } else {
+                    ControlFlow::Continue(())
+                }
+            }
+            LifetimeData::InferenceVar(var) => visitor.visit_inference_var(*var, outer_binder),
+            LifetimeData::Placeholder(universe) => {
+                visitor.visit_free_placeholder(*universe, outer_binder)
+            }
+            LifetimeData::Static | LifetimeData::Erased => ControlFlow::Continue(()),
+            LifetimeData::Phantom(void, ..) => match *void {},
+        }
+    }
+}
+
+impl<I: Interner> TypeVisitable<I> for Const<I> {
+    fn visit_with<B>(
+        &self,
+        visitor: &mut dyn TypeVisitor<I, BreakTy = B>,
+        outer_binder: DebruijnIndex,
+    ) -> ControlFlow<B> {
+        visitor.visit_const(self, outer_binder)
+    }
+}
+
+impl<I: Interner> TypeSuperVisitable<I> for Const<I> {
+    fn super_visit_with<B>(
+        &self,
+        visitor: &mut dyn TypeVisitor<I, BreakTy = B>,
+        outer_binder: DebruijnIndex,
+    ) -> ControlFlow<B> {
+        let interner = visitor.interner();
+        match &self.data(interner).value {
+            ConstValue::BoundVar(bound_var) => {
+                if bound_var.shifted_out_to(outer_binder).is_some() {
+                    visitor.visit_free_var(*bound_var, outer_binder)
+                } else {
+                    ControlFlow::Continue(())
+                }
+            }
+            ConstValue::InferenceVar(var) => visitor.visit_inference_var(*var, outer_binder),
+            ConstValue::Placeholder(universe) => {
+                visitor.visit_free_placeholder(*universe, outer_binder)
+            }
+            ConstValue::Concrete(_) => ControlFlow::Continue(()),
+        }
+    }
+}
+
+impl<I: Interner> TypeVisitable<I> for Goal<I> {
+    fn visit_with<B>(
+        &self,
+        visitor: &mut dyn TypeVisitor<I, BreakTy = B>,
+        outer_binder: DebruijnIndex,
+    ) -> ControlFlow<B> {
+        visitor.visit_goal(self, outer_binder)
+    }
+}
+
+impl<I: Interner> TypeSuperVisitable<I> for Goal<I> {
+    fn super_visit_with<B>(
+        &self,
+        visitor: &mut dyn TypeVisitor<I, BreakTy = B>,
+        outer_binder: DebruijnIndex,
+    ) -> ControlFlow<B> {
+        let interner = visitor.interner();
+        self.data(interner).visit_with(visitor, outer_binder)
+    }
+}
+
+impl<I: Interner> TypeVisitable<I> for ProgramClause<I> {
+    fn visit_with<B>(
+        &self,
+        visitor: &mut dyn TypeVisitor<I, BreakTy = B>,
+        outer_binder: DebruijnIndex,
+    ) -> ControlFlow<B> {
+        visitor.visit_program_clause(self, outer_binder)
+    }
+}
+
+impl<I: Interner> TypeVisitable<I> for WhereClause<I> {
+    fn visit_with<B>(
+        &self,
+        visitor: &mut dyn TypeVisitor<I, BreakTy = B>,
+        outer_binder: DebruijnIndex,
+    ) -> ControlFlow<B> {
+        visitor.visit_where_clause(self, outer_binder)
+    }
+}
+
+impl<I: Interner> TypeVisitable<I> for DomainGoal<I> {
+    fn visit_with<B>(
+        &self,
+        visitor: &mut dyn TypeVisitor<I, BreakTy = B>,
+        outer_binder: DebruijnIndex,
+    ) -> ControlFlow<B> {
+        visitor.visit_domain_goal(self, outer_binder)
+    }
+}