Merging upstream version 1.68.2+dfsg1.

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

19 files changed, 0 insertions, 8500 deletions

diff --git a/vendor/chalk-ir/.cargo-checksum.json b/vendor/chalk-ir/.cargo-checksum.json
deleted file mode 100644
index 7b2915873..000000000
--- a/vendor/chalk-ir/.cargo-checksum.json
+++ /dev/null
@@ -1 +0,0 @@
-{"files":{"Cargo.toml":"ccde3a8b1652787636f0a34b43eb557bfce1e7e9a92b4634a6f666e512d8d491","README.md":"64cba0ddf3e9b5c168fbe069f1a84c401ce0b33e765ea49acb1345d0923afe8d","src/cast.rs":"b2a6dc2fe33d58df3021d1e83f3823d68a14afff2a484fe0a5c8514290112c17","src/could_match.rs":"a341b8b11615ca738498c722b61695307da170f14754c281fbf2b778d3e82348","src/debug.rs":"63c152c41ae1adcdd1cca725162bef1b42e19307d3b4dfc228d43743d6c6daf2","src/fold.rs":"aa00b9aed253895eb532ba0f89dfb5e971743ea258437cea492c2f90f01c9b23","src/fold/binder_impls.rs":"47ee10eac8081e15148a43e9a1dae32712b0b14d565c9ed5082985abda9302a4","src/fold/boring_impls.rs":"6958c7d0d8315d6864b4d2ec4638544567d6262e1f50fb28df02ac1d57804d90","src/fold/in_place.rs":"83bf2fb5d2b6d8fcd7a2389779329cfc72e83b223eb9dac899635e2deab5a9c9","src/fold/shift.rs":"4119c8e3bb40279ab416ace3bea2137fc917440bb50b37c870c56f9351d508db","src/fold/subst.rs":"6254d62b2bf92d8114384701734a53780119836b0aaf87392dda161ea7b93526","src/interner.rs":"41f5780894b29542db0f7a46386e60f321c527bfd02cbf5be89b45be14a4dc3c","src/lib.rs":"e7fd2eab6a8cae0b0e8bce4b2a0fcb7a67da991755b11d9e9351ba2ec0cf5f87","src/visit.rs":"c914621e2bb77290b3d064cd52d4703ad438daa0c167f8fe0c3fb696a2674b84","src/visit/binder_impls.rs":"9afc460830fd9de249c4120461624432edf715e8661cf28c36e9f2ff47e2a13e","src/visit/boring_impls.rs":"412cdfc9f78edf3a5f6d6ad2f60e21087263c74bca1236420115608333ae9704","src/visit/visitors.rs":"3af422b5179a364483575eec03d68cb277a308508b89a19915f4d76aed9dc696","src/zip.rs":"d86c20f0d44ecf6dae9dae02540d0beb04081a7721337a9dfa3c1b0a4b8cb4f7"},"package":"43aa55deff4e7fbdb09fa014543372f2c95a06835ac487b9ce57b5099b950838"}
\ No newline at end of file
diff --git a/vendor/chalk-ir/Cargo.toml b/vendor/chalk-ir/Cargo.toml
deleted file mode 100644
index 16e1e83b2..000000000
--- a/vendor/chalk-ir/Cargo.toml
+++ /dev/null
@@ -1,37 +0,0 @@
-# THIS FILE IS AUTOMATICALLY GENERATED BY CARGO
-#
-# When uploading crates to the registry Cargo will automatically
-# "normalize" Cargo.toml files for maximal compatibility
-# with all versions of Cargo and also rewrite `path` dependencies
-# to registry (e.g., crates.io) dependencies.
-#
-# If you are reading this file be aware that the original Cargo.toml
-# will likely look very different (and much more reasonable).
-# See Cargo.toml.orig for the original contents.
-
-[package]
-edition = "2018"
-name = "chalk-ir"
-version = "0.87.0"
-authors = [
-    "Rust Compiler Team",
-    "Chalk developers",
-]
-description = "Chalk's internal representation of types, goals, and clauses"
-readme = "README.md"
-keywords = [
-    "compiler",
-    "traits",
-    "prolog",
-]
-license = "MIT OR Apache-2.0"
-repository = "https://github.com/rust-lang/chalk"
-
-[dependencies.bitflags]
-version = "1.2.1"
-
-[dependencies.chalk-derive]
-version = "=0.87.0"
-
-[dependencies.lazy_static]
-version = "1.4.0"
diff --git a/vendor/chalk-ir/README.md b/vendor/chalk-ir/README.md
deleted file mode 100644
index 968ad4937..000000000
--- a/vendor/chalk-ir/README.md
+++ /dev/null
@@ -1,3 +0,0 @@
-A rust type library for chalk.
-
-See [Github](https://github.com/rust-lang/chalk) for up-to-date information.
diff --git a/vendor/chalk-ir/src/cast.rs b/vendor/chalk-ir/src/cast.rs
deleted file mode 100644
index 0c6b682ca..000000000
--- a/vendor/chalk-ir/src/cast.rs
+++ /dev/null
@@ -1,364 +0,0 @@
-//! Upcasts, to avoid writing out wrapper types.
-
-use crate::*;
-use std::marker::PhantomData;
-
-/// The `Cast` trait is used to make annoying upcasts between
-/// logically equivalent types that imply wrappers. For example, one
-/// could convert a `DomainGoal` into a `Goal` by doing:
-///
-/// ```ignore
-/// let goal: Goal = domain_goal.cast();
-/// ```
-///
-/// This is equivalent to the more explicit:
-///
-/// ```ignore
-/// let goal: Goal = Goal::DomainGoal(domain_goal)
-/// ```
-///
-/// Another useful trick is the `casted()` iterator adapter, which
-/// casts each element in the iterator as it is produced (you must
-/// have the `Caster` trait in scope for that).
-///
-/// # Invariant
-///
-/// `Cast` imposes a key invariant. You can only implement `T:
-/// Cast<U>` if both `T` and `U` have the same semantic meaning. Also,
-/// as part of this, they should always use the same set of free
-/// variables (the `Canonical` implementation, for example, relies on
-/// that).
-///
-/// # Iterators
-///
-/// If you import the `Caster` trait, you can also write `.casted()` on an
-/// iterator chain to cast every instance within.
-///
-/// # Implementing Cast
-///
-/// Do not implement `Cast` directly. Instead, implement `CastTo`.
-/// This split setup allows us to write `foo.cast::<T>()` to mean
-/// "cast to T".
-pub trait Cast: Sized {
-    /// Cast a value to type `U` using `CastTo`.
-    fn cast<U>(self, interner: U::Interner) -> U
-    where
-        Self: CastTo<U>,
-        U: HasInterner,
-    {
-        self.cast_to(interner)
-    }
-}
-
-impl<T> Cast for T {}
-
-/// The "helper" trait for `cast` that actually implements the
-/// transformations. You can also use this if you want to have
-/// functions that take (e.g.) an `impl CastTo<Goal<_>>` or something
-/// like that.
-pub trait CastTo<T: HasInterner>: Sized {
-    /// Cast a value to type `T`.
-    fn cast_to(self, interner: T::Interner) -> T;
-}
-
-macro_rules! reflexive_impl {
-    (for($($t:tt)*) $u:ty) => {
-        impl<$($t)*> CastTo<$u> for $u {
-            fn cast_to(self, _interner: <$u as HasInterner>::Interner) -> $u {
-                self
-            }
-        }
-    };
-    ($u:ty) => {
-        impl CastTo<$u> for $u {
-            fn cast_to(self, interner: <$u as HasInterner>::Interner) -> $u {
-                self
-            }
-        }
-    };
-}
-
-reflexive_impl!(for(I: Interner) TyKind<I>);
-reflexive_impl!(for(I: Interner) LifetimeData<I>);
-reflexive_impl!(for(I: Interner) ConstData<I>);
-reflexive_impl!(for(I: Interner) TraitRef<I>);
-reflexive_impl!(for(I: Interner) DomainGoal<I>);
-reflexive_impl!(for(I: Interner) Goal<I>);
-reflexive_impl!(for(I: Interner) WhereClause<I>);
-reflexive_impl!(for(I: Interner) ProgramClause<I>);
-reflexive_impl!(for(I: Interner) QuantifiedWhereClause<I>);
-reflexive_impl!(for(I: Interner) VariableKind<I>);
-reflexive_impl!(for(I: Interner) VariableKinds<I>);
-reflexive_impl!(for(I: Interner) CanonicalVarKind<I>);
-reflexive_impl!(for(I: Interner) CanonicalVarKinds<I>);
-reflexive_impl!(for(I: Interner) Constraint<I>);
-
-impl<I: Interner> CastTo<WhereClause<I>> for TraitRef<I> {
-    fn cast_to(self, _interner: I) -> WhereClause<I> {
-        WhereClause::Implemented(self)
-    }
-}
-
-impl<I: Interner> CastTo<WhereClause<I>> for AliasEq<I> {
-    fn cast_to(self, _interner: I) -> WhereClause<I> {
-        WhereClause::AliasEq(self)
-    }
-}
-
-impl<I: Interner> CastTo<WhereClause<I>> for LifetimeOutlives<I> {
-    fn cast_to(self, _interner: I) -> WhereClause<I> {
-        WhereClause::LifetimeOutlives(self)
-    }
-}
-
-impl<I: Interner> CastTo<WhereClause<I>> for TypeOutlives<I> {
-    fn cast_to(self, _interner: I) -> WhereClause<I> {
-        WhereClause::TypeOutlives(self)
-    }
-}
-
-impl<T, I> CastTo<DomainGoal<I>> for T
-where
-    T: CastTo<WhereClause<I>>,
-    I: Interner,
-{
-    fn cast_to(self, interner: I) -> DomainGoal<I> {
-        DomainGoal::Holds(self.cast(interner))
-    }
-}
-
-impl<T, I: Interner> CastTo<Goal<I>> for T
-where
-    T: CastTo<DomainGoal<I>>,
-{
-    fn cast_to(self, interner: I) -> Goal<I> {
-        GoalData::DomainGoal(self.cast(interner)).intern(interner)
-    }
-}
-
-impl<I: Interner> CastTo<DomainGoal<I>> for Normalize<I> {
-    fn cast_to(self, _interner: I) -> DomainGoal<I> {
-        DomainGoal::Normalize(self)
-    }
-}
-
-impl<I: Interner> CastTo<DomainGoal<I>> for WellFormed<I> {
-    fn cast_to(self, _interner: I) -> DomainGoal<I> {
-        DomainGoal::WellFormed(self)
-    }
-}
-
-impl<I: Interner> CastTo<DomainGoal<I>> for FromEnv<I> {
-    fn cast_to(self, _interner: I) -> DomainGoal<I> {
-        DomainGoal::FromEnv(self)
-    }
-}
-
-impl<I: Interner> CastTo<Goal<I>> for EqGoal<I> {
-    fn cast_to(self, interner: I) -> Goal<I> {
-        GoalData::EqGoal(self).intern(interner)
-    }
-}
-
-impl<I: Interner> CastTo<Goal<I>> for SubtypeGoal<I> {
-    fn cast_to(self, interner: I) -> Goal<I> {
-        GoalData::SubtypeGoal(self).intern(interner)
-    }
-}
-
-impl<I: Interner, T: HasInterner<Interner = I> + CastTo<Goal<I>>> CastTo<Goal<I>> for Binders<T> {
-    fn cast_to(self, interner: I) -> Goal<I> {
-        GoalData::Quantified(
-            QuantifierKind::ForAll,
-            self.map(|bound| bound.cast(interner)),
-        )
-        .intern(interner)
-    }
-}
-
-impl<I: Interner> CastTo<TyKind<I>> for AliasTy<I> {
-    fn cast_to(self, _interner: I) -> TyKind<I> {
-        TyKind::Alias(self)
-    }
-}
-
-impl<I: Interner> CastTo<GenericArg<I>> for Ty<I> {
-    fn cast_to(self, interner: I) -> GenericArg<I> {
-        GenericArg::new(interner, GenericArgData::Ty(self))
-    }
-}
-
-impl<I: Interner> CastTo<GenericArg<I>> for Lifetime<I> {
-    fn cast_to(self, interner: I) -> GenericArg<I> {
-        GenericArg::new(interner, GenericArgData::Lifetime(self))
-    }
-}
-
-impl<I: Interner> CastTo<GenericArg<I>> for Const<I> {
-    fn cast_to(self, interner: I) -> GenericArg<I> {
-        GenericArg::new(interner, GenericArgData::Const(self))
-    }
-}
-
-impl<I: Interner> CastTo<GenericArg<I>> for GenericArg<I> {
-    fn cast_to(self, _interner: I) -> GenericArg<I> {
-        self
-    }
-}
-
-impl<T, I> CastTo<ProgramClause<I>> for T
-where
-    T: CastTo<DomainGoal<I>>,
-    I: Interner,
-{
-    fn cast_to(self, interner: I) -> ProgramClause<I> {
-        let implication = ProgramClauseImplication {
-            consequence: self.cast(interner),
-            conditions: Goals::empty(interner),
-            constraints: Constraints::empty(interner),
-            priority: ClausePriority::High,
-        };
-
-        ProgramClauseData(Binders::empty(interner, implication.shifted_in(interner)))
-            .intern(interner)
-    }
-}
-
-impl<I, T> CastTo<ProgramClause<I>> for Binders<T>
-where
-    I: Interner,
-    T: HasInterner<Interner = I> + CastTo<DomainGoal<I>>,
-{
-    fn cast_to(self, interner: I) -> ProgramClause<I> {
-        ProgramClauseData(self.map(|bound| ProgramClauseImplication {
-            consequence: bound.cast(interner),
-            conditions: Goals::empty(interner),
-            constraints: Constraints::empty(interner),
-            priority: ClausePriority::High,
-        }))
-        .intern(interner)
-    }
-}
-
-impl<T, U> CastTo<Option<U>> for Option<T>
-where
-    T: CastTo<U>,
-    U: HasInterner,
-{
-    fn cast_to(self, interner: U::Interner) -> Option<U> {
-        self.map(|v| v.cast(interner))
-    }
-}
-
-impl<T, U, I> CastTo<InEnvironment<U>> for InEnvironment<T>
-where
-    T: HasInterner<Interner = I> + CastTo<U>,
-    U: HasInterner<Interner = I>,
-    I: Interner,
-{
-    fn cast_to(self, interner: U::Interner) -> InEnvironment<U> {
-        self.map(|v| v.cast(interner))
-    }
-}
-
-impl<T, U, E> CastTo<Result<U, E>> for Result<T, E>
-where
-    T: CastTo<U>,
-    U: HasInterner,
-{
-    fn cast_to(self, interner: U::Interner) -> Result<U, E> {
-        self.map(|v| v.cast(interner))
-    }
-}
-
-impl<T> HasInterner for Option<T>
-where
-    T: HasInterner,
-{
-    type Interner = T::Interner;
-}
-
-impl<T, E> HasInterner for Result<T, E>
-where
-    T: HasInterner,
-{
-    type Interner = T::Interner;
-}
-
-impl<T, U> CastTo<Canonical<U>> for Canonical<T>
-where
-    T: CastTo<U> + HasInterner,
-    U: HasInterner<Interner = T::Interner>,
-{
-    fn cast_to(self, interner: T::Interner) -> Canonical<U> {
-        // Subtle point: It should be ok to re-use the binders here,
-        // because `cast()` never introduces new inference variables,
-        // nor changes the "substance" of the type we are working
-        // with. It just introduces new wrapper types.
-        Canonical {
-            value: self.value.cast(interner),
-            binders: self.binders.cast(interner),
-        }
-    }
-}
-
-impl<T, U> CastTo<Vec<U>> for Vec<T>
-where
-    T: CastTo<U> + HasInterner,
-    U: HasInterner,
-{
-    fn cast_to(self, interner: U::Interner) -> Vec<U> {
-        self.into_iter().casted(interner).collect()
-    }
-}
-
-impl<T> CastTo<T> for &T
-where
-    T: Clone + HasInterner,
-{
-    fn cast_to(self, _interner: T::Interner) -> T {
-        self.clone()
-    }
-}
-
-/// An iterator that casts each element to some other type.
-pub struct Casted<IT, U: HasInterner> {
-    interner: U::Interner,
-    iterator: IT,
-    _cast: PhantomData<U>,
-}
-
-impl<IT: Iterator, U> Iterator for Casted<IT, U>
-where
-    IT::Item: CastTo<U>,
-    U: HasInterner,
-{
-    type Item = U;
-
-    fn next(&mut self) -> Option<Self::Item> {
-        self.iterator.next().map(|item| item.cast_to(self.interner))
-    }
-
-    fn size_hint(&self) -> (usize, Option<usize>) {
-        self.iterator.size_hint()
-    }
-}
-
-/// An iterator adapter that casts each element we are iterating over
-/// to some other type.
-pub trait Caster: Iterator + Sized {
-    /// Cast each element in this iterator.
-    fn casted<U>(self, interner: U::Interner) -> Casted<Self, U>
-    where
-        Self::Item: CastTo<U>,
-        U: HasInterner,
-    {
-        Casted {
-            interner,
-            iterator: self,
-            _cast: PhantomData,
-        }
-    }
-}
-
-impl<I> Caster for I where I: Iterator {}
diff --git a/vendor/chalk-ir/src/could_match.rs b/vendor/chalk-ir/src/could_match.rs
deleted file mode 100644
index 9f94ff47a..000000000
--- a/vendor/chalk-ir/src/could_match.rs
+++ /dev/null
@@ -1,213 +0,0 @@
-//! Fast matching check for zippable values.
-
-use crate::interner::HasInterner;
-use crate::zip::{Zip, Zipper};
-use crate::*;
-
-/// A fast check to see whether two things could ever possibly match.
-pub trait CouldMatch<T: ?Sized + HasInterner> {
-    /// Checks whether `self` and `other` could possibly match.
-    fn could_match(
-        &self,
-        interner: T::Interner,
-        db: &dyn UnificationDatabase<T::Interner>,
-        other: &T,
-    ) -> bool;
-}
-
-#[allow(unreachable_code, unused_variables)]
-impl<T, I> CouldMatch<T> for T
-where
-    T: Zip<I> + ?Sized + HasInterner<Interner = I>,
-    I: Interner,
-{
-    fn could_match(&self, interner: I, db: &dyn UnificationDatabase<I>, other: &T) -> bool {
-        return Zip::zip_with(
-            &mut MatchZipper { interner, db },
-            Variance::Invariant,
-            self,
-            other,
-        )
-        .is_ok();
-
-        struct MatchZipper<'i, I> {
-            interner: I,
-            db: &'i dyn UnificationDatabase<I>,
-        }
-
-        impl<'i, I: Interner> Zipper<I> for MatchZipper<'i, I> {
-            fn zip_tys(&mut self, variance: Variance, a: &Ty<I>, b: &Ty<I>) -> Fallible<()> {
-                let interner = self.interner;
-                let matches = |a: &Substitution<I>, b: &Substitution<I>| {
-                    a.iter(interner)
-                        .zip(b.iter(interner))
-                        .all(|(p_a, p_b)| p_a.could_match(interner, self.db, p_b))
-                };
-                let could_match = match (a.kind(interner), b.kind(interner)) {
-                    (TyKind::Adt(id_a, substitution_a), TyKind::Adt(id_b, substitution_b)) => {
-                        id_a == id_b
-                            && self
-                                .zip_substs(
-                                    variance,
-                                    Some(self.unification_database().adt_variance(*id_a)),
-                                    substitution_a.as_slice(interner),
-                                    substitution_b.as_slice(interner),
-                                )
-                                .is_ok()
-                    }
-                    (
-                        TyKind::AssociatedType(assoc_ty_a, substitution_a),
-                        TyKind::AssociatedType(assoc_ty_b, substitution_b),
-                    ) => assoc_ty_a == assoc_ty_b && matches(substitution_a, substitution_b),
-                    (TyKind::Scalar(scalar_a), TyKind::Scalar(scalar_b)) => scalar_a == scalar_b,
-                    (TyKind::Str, TyKind::Str) => true,
-                    (
-                        TyKind::Tuple(arity_a, substitution_a),
-                        TyKind::Tuple(arity_b, substitution_b),
-                    ) => arity_a == arity_b && matches(substitution_a, substitution_b),
-                    (
-                        TyKind::OpaqueType(opaque_ty_a, substitution_a),
-                        TyKind::OpaqueType(opaque_ty_b, substitution_b),
-                    ) => opaque_ty_a == opaque_ty_b && matches(substitution_a, substitution_b),
-                    (TyKind::Slice(ty_a), TyKind::Slice(ty_b)) => {
-                        ty_a.could_match(interner, self.db, ty_b)
-                    }
-                    (
-                        TyKind::FnDef(fn_def_a, substitution_a),
-                        TyKind::FnDef(fn_def_b, substitution_b),
-                    ) => {
-                        fn_def_a == fn_def_b
-                            && self
-                                .zip_substs(
-                                    variance,
-                                    Some(self.unification_database().fn_def_variance(*fn_def_a)),
-                                    substitution_a.as_slice(interner),
-                                    substitution_b.as_slice(interner),
-                                )
-                                .is_ok()
-                    }
-                    (
-                        TyKind::Ref(mutability_a, lifetime_a, ty_a),
-                        TyKind::Ref(mutability_b, lifetime_b, ty_b),
-                    ) => {
-                        mutability_a == mutability_b
-                            && lifetime_a.could_match(interner, self.db, lifetime_b)
-                            && ty_a.could_match(interner, self.db, ty_b)
-                    }
-                    (TyKind::Raw(mutability_a, ty_a), TyKind::Raw(mutability_b, ty_b)) => {
-                        mutability_a == mutability_b && ty_a.could_match(interner, self.db, ty_b)
-                    }
-                    (TyKind::Never, TyKind::Never) => true,
-                    (TyKind::Array(ty_a, const_a), TyKind::Array(ty_b, const_b)) => {
-                        ty_a.could_match(interner, self.db, ty_b)
-                            && const_a.could_match(interner, self.db, const_b)
-                    }
-                    (
-                        TyKind::Closure(id_a, substitution_a),
-                        TyKind::Closure(id_b, substitution_b),
-                    ) => id_a == id_b && matches(substitution_a, substitution_b),
-                    (
-                        TyKind::Generator(generator_a, substitution_a),
-                        TyKind::Generator(generator_b, substitution_b),
-                    ) => {
-                        generator_a == generator_b
-                            && self
-                                .zip_substs(
-                                    variance,
-                                    None,
-                                    substitution_a.as_slice(interner),
-                                    substitution_b.as_slice(interner),
-                                )
-                                .is_ok()
-                    }
-                    (
-                        TyKind::GeneratorWitness(generator_a, substitution_a),
-                        TyKind::GeneratorWitness(generator_b, substitution_b),
-                    ) => {
-                        generator_a == generator_b
-                            && self
-                                .zip_substs(
-                                    variance,
-                                    None,
-                                    substitution_a.as_slice(interner),
-                                    substitution_b.as_slice(interner),
-                                )
-                                .is_ok()
-                    }
-                    (TyKind::Foreign(foreign_ty_a), TyKind::Foreign(foreign_ty_b)) => {
-                        foreign_ty_a == foreign_ty_b
-                    }
-                    (TyKind::Error, TyKind::Error) => true,
-
-                    _ => true,
-                };
-
-                if could_match {
-                    Ok(())
-                } else {
-                    Err(NoSolution)
-                }
-            }
-
-            fn zip_lifetimes(
-                &mut self,
-                variance: Variance,
-                _: &Lifetime<I>,
-                _: &Lifetime<I>,
-            ) -> Fallible<()> {
-                Ok(())
-            }
-
-            fn zip_consts(
-                &mut self,
-                variance: Variance,
-                _: &Const<I>,
-                _: &Const<I>,
-            ) -> Fallible<()> {
-                Ok(())
-            }
-
-            fn zip_binders<T>(
-                &mut self,
-                variance: Variance,
-                a: &Binders<T>,
-                b: &Binders<T>,
-            ) -> Fallible<()>
-            where
-                T: HasInterner + Zip<I>,
-            {
-                Zip::zip_with(self, variance, &a.value, &b.value)
-            }
-
-            fn interner(&self) -> I {
-                self.interner
-            }
-
-            fn unification_database(&self) -> &dyn UnificationDatabase<I> {
-                self.db
-            }
-        }
-    }
-}
-
-impl<I: Interner> CouldMatch<DomainGoal<I>> for ProgramClauseData<I> {
-    fn could_match(
-        &self,
-        interner: I,
-        db: &dyn UnificationDatabase<I>,
-        other: &DomainGoal<I>,
-    ) -> bool {
-        self.0.value.consequence.could_match(interner, db, other)
-    }
-}
-
-impl<I: Interner> CouldMatch<DomainGoal<I>> for ProgramClause<I> {
-    fn could_match(
-        &self,
-        interner: I,
-        db: &dyn UnificationDatabase<I>,
-        other: &DomainGoal<I>,
-    ) -> bool {
-        self.data(interner).could_match(interner, db, other)
-    }
-}
diff --git a/vendor/chalk-ir/src/debug.rs b/vendor/chalk-ir/src/debug.rs
deleted file mode 100644
index 76d66edf5..000000000
--- a/vendor/chalk-ir/src/debug.rs
+++ /dev/null
@@ -1,1016 +0,0 @@
-//! Debug impls for types.
-
-use std::fmt::{self, Debug, Display, Error, Formatter};
-
-use super::*;
-
-/// Wrapper to allow forwarding to `Display::fmt`, `Debug::fmt`, etc.
-pub struct Fmt<F>(pub F)
-where
-    F: Fn(&mut fmt::Formatter<'_>) -> fmt::Result;
-
-impl<F> fmt::Display for Fmt<F>
-where
-    F: Fn(&mut fmt::Formatter<'_>) -> fmt::Result,
-{
-    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        (self.0)(f)
-    }
-}
-
-impl<I: Interner> Debug for TraitId<I> {
-    fn fmt(&self, fmt: &mut Formatter<'_>) -> Result<(), Error> {
-        I::debug_trait_id(*self, fmt).unwrap_or_else(|| write!(fmt, "TraitId({:?})", self.0))
-    }
-}
-
-impl<I: Interner> Debug for AdtId<I> {
-    fn fmt(&self, fmt: &mut Formatter<'_>) -> Result<(), Error> {
-        I::debug_adt_id(*self, fmt).unwrap_or_else(|| write!(fmt, "AdtId({:?})", self.0))
-    }
-}
-
-impl<I: Interner> Debug for AssocTypeId<I> {
-    fn fmt(&self, fmt: &mut Formatter<'_>) -> Result<(), Error> {
-        I::debug_assoc_type_id(*self, fmt)
-            .unwrap_or_else(|| write!(fmt, "AssocTypeId({:?})", self.0))
-    }
-}
-
-impl<I: Interner> Debug for FnDefId<I> {
-    fn fmt(&self, fmt: &mut Formatter<'_>) -> std::fmt::Result {
-        I::debug_fn_def_id(*self, fmt).unwrap_or_else(|| write!(fmt, "FnDefId({:?})", self.0))
-    }
-}
-
-impl<I: Interner> Debug for ClosureId<I> {
-    fn fmt(&self, fmt: &mut Formatter<'_>) -> std::fmt::Result {
-        I::debug_closure_id(*self, fmt).unwrap_or_else(|| write!(fmt, "ClosureId({:?})", self.0))
-    }
-}
-
-impl<I: Interner> Debug for GeneratorId<I> {
-    fn fmt(&self, fmt: &mut Formatter<'_>) -> std::fmt::Result {
-        I::debug_generator_id(*self, fmt)
-            .unwrap_or_else(|| write!(fmt, "GeneratorId({:?})", self.0))
-    }
-}
-
-impl<I: Interner> Debug for ForeignDefId<I> {
-    fn fmt(&self, fmt: &mut Formatter<'_>) -> std::fmt::Result {
-        I::debug_foreign_def_id(*self, fmt)
-            .unwrap_or_else(|| write!(fmt, "ForeignDefId({:?})", self.0))
-    }
-}
-
-impl<I: Interner> Debug for Ty<I> {
-    fn fmt(&self, fmt: &mut Formatter<'_>) -> Result<(), Error> {
-        I::debug_ty(self, fmt).unwrap_or_else(|| write!(fmt, "{:?}", self.interned))
-    }
-}
-
-impl<I: Interner> Debug for Lifetime<I> {
-    fn fmt(&self, fmt: &mut Formatter<'_>) -> Result<(), Error> {
-        I::debug_lifetime(self, fmt).unwrap_or_else(|| write!(fmt, "{:?}", self.interned))
-    }
-}
-
-impl<I: Interner> Debug for Const<I> {
-    fn fmt(&self, fmt: &mut Formatter<'_>) -> Result<(), Error> {
-        I::debug_const(self, fmt).unwrap_or_else(|| write!(fmt, "{:?}", self.interned))
-    }
-}
-
-impl<I: Interner> Debug for ConcreteConst<I> {
-    fn fmt(&self, fmt: &mut Formatter<'_>) -> Result<(), Error> {
-        write!(fmt, "{:?}", self.interned)
-    }
-}
-
-impl<I: Interner> Debug for GenericArg<I> {
-    fn fmt(&self, fmt: &mut Formatter<'_>) -> Result<(), Error> {
-        I::debug_generic_arg(self, fmt).unwrap_or_else(|| write!(fmt, "{:?}", self.interned))
-    }
-}
-
-impl<I: Interner> Debug for Goal<I> {
-    fn fmt(&self, fmt: &mut Formatter<'_>) -> Result<(), Error> {
-        I::debug_goal(self, fmt).unwrap_or_else(|| write!(fmt, "{:?}", self.interned))
-    }
-}
-
-impl<I: Interner> Debug for Goals<I> {
-    fn fmt(&self, fmt: &mut Formatter<'_>) -> Result<(), Error> {
-        I::debug_goals(self, fmt).unwrap_or_else(|| write!(fmt, "{:?}", self.interned))
-    }
-}
-
-impl<I: Interner> Debug for ProgramClauseImplication<I> {
-    fn fmt(&self, fmt: &mut Formatter<'_>) -> Result<(), Error> {
-        I::debug_program_clause_implication(self, fmt)
-            .unwrap_or_else(|| write!(fmt, "ProgramClauseImplication(?)"))
-    }
-}
-
-impl<I: Interner> Debug for ProgramClause<I> {
-    fn fmt(&self, fmt: &mut Formatter<'_>) -> Result<(), Error> {
-        I::debug_program_clause(self, fmt).unwrap_or_else(|| write!(fmt, "{:?}", self.interned))
-    }
-}
-
-impl<I: Interner> Debug for ProgramClauses<I> {
-    fn fmt(&self, fmt: &mut Formatter<'_>) -> Result<(), Error> {
-        I::debug_program_clauses(self, fmt).unwrap_or_else(|| write!(fmt, "{:?}", self.interned))
-    }
-}
-
-impl<I: Interner> Debug for Constraints<I> {
-    fn fmt(&self, fmt: &mut Formatter<'_>) -> Result<(), Error> {
-        I::debug_constraints(self, fmt).unwrap_or_else(|| write!(fmt, "{:?}", self.interned))
-    }
-}
-
-impl<I: Interner> Debug for SeparatorTraitRef<'_, I> {
-    fn fmt(&self, fmt: &mut Formatter<'_>) -> Result<(), Error> {
-        I::debug_separator_trait_ref(self, fmt)
-            .unwrap_or_else(|| write!(fmt, "SeparatorTraitRef(?)"))
-    }
-}
-
-impl<I: Interner> Debug for AliasTy<I> {
-    fn fmt(&self, fmt: &mut Formatter<'_>) -> Result<(), Error> {
-        I::debug_alias(self, fmt).unwrap_or_else(|| write!(fmt, "AliasTy(?)"))
-    }
-}
-
-impl<I: Interner> Debug for QuantifiedWhereClauses<I> {
-    fn fmt(&self, fmt: &mut Formatter<'_>) -> Result<(), Error> {
-        I::debug_quantified_where_clauses(self, fmt)
-            .unwrap_or_else(|| write!(fmt, "{:?}", self.interned))
-    }
-}
-
-impl<I: Interner> Debug for ProjectionTy<I> {
-    fn fmt(&self, fmt: &mut Formatter<'_>) -> Result<(), Error> {
-        I::debug_projection_ty(self, fmt).unwrap_or_else(|| {
-            unimplemented!("cannot format ProjectionTy without setting Program in tls")
-        })
-    }
-}
-
-impl<I: Interner> Debug for OpaqueTy<I> {
-    fn fmt(&self, fmt: &mut Formatter<'_>) -> Result<(), Error> {
-        I::debug_opaque_ty(self, fmt).unwrap_or_else(|| {
-            unimplemented!("cannot format OpaqueTy without setting Program in tls")
-        })
-    }
-}
-
-impl<I: Interner> Display for Substitution<I> {
-    fn fmt(&self, fmt: &mut Formatter<'_>) -> Result<(), Error> {
-        I::debug_substitution(self, fmt).unwrap_or_else(|| write!(fmt, "{:?}", self.interned))
-    }
-}
-
-impl<I: Interner> Debug for OpaqueTyId<I> {
-    fn fmt(&self, fmt: &mut Formatter<'_>) -> Result<(), Error> {
-        I::debug_opaque_ty_id(*self, fmt).unwrap_or_else(|| write!(fmt, "OpaqueTyId({:?})", self.0))
-    }
-}
-
-impl Display for UniverseIndex {
-    fn fmt(&self, fmt: &mut Formatter<'_>) -> Result<(), Error> {
-        write!(fmt, "U{}", self.counter)
-    }
-}
-
-impl Debug for UniverseIndex {
-    fn fmt(&self, fmt: &mut Formatter<'_>) -> Result<(), Error> {
-        write!(fmt, "U{}", self.counter)
-    }
-}
-
-impl<I: Interner> Debug for TyData<I> {
-    fn fmt(&self, fmt: &mut Formatter<'_>) -> Result<(), Error> {
-        self.kind.fmt(fmt)
-    }
-}
-
-impl<I: Interner> Debug for TyKind<I> {
-    fn fmt(&self, fmt: &mut Formatter<'_>) -> Result<(), Error> {
-        match self {
-            TyKind::BoundVar(db) => write!(fmt, "{:?}", db),
-            TyKind::Dyn(clauses) => write!(fmt, "{:?}", clauses),
-            TyKind::InferenceVar(var, TyVariableKind::General) => write!(fmt, "{:?}", var),
-            TyKind::InferenceVar(var, TyVariableKind::Integer) => write!(fmt, "{:?}i", var),
-            TyKind::InferenceVar(var, TyVariableKind::Float) => write!(fmt, "{:?}f", var),
-            TyKind::Alias(alias) => write!(fmt, "{:?}", alias),
-            TyKind::Placeholder(index) => write!(fmt, "{:?}", index),
-            TyKind::Function(function) => write!(fmt, "{:?}", function),
-            TyKind::Adt(id, substitution) => write!(fmt, "{:?}<{:?}>", id, substitution),
-            TyKind::AssociatedType(assoc_ty, substitution) => {
-                write!(fmt, "{:?}<{:?}>", assoc_ty, substitution)
-            }
-            TyKind::Scalar(scalar) => write!(fmt, "{:?}", scalar),
-            TyKind::Str => write!(fmt, "Str"),
-            TyKind::Tuple(arity, substitution) => write!(fmt, "{:?}<{:?}>", arity, substitution),
-            TyKind::OpaqueType(opaque_ty, substitution) => {
-                write!(fmt, "!{:?}<{:?}>", opaque_ty, substitution)
-            }
-            TyKind::Slice(substitution) => write!(fmt, "{{slice}}<{:?}>", substitution),
-            TyKind::FnDef(fn_def, substitution) => write!(fmt, "{:?}<{:?}>", fn_def, substitution),
-            TyKind::Ref(mutability, lifetime, ty) => match mutability {
-                Mutability::Mut => write!(fmt, "(&{:?} mut {:?})", lifetime, ty),
-                Mutability::Not => write!(fmt, "(&{:?} {:?})", lifetime, ty),
-            },
-            TyKind::Raw(mutability, ty) => match mutability {
-                Mutability::Mut => write!(fmt, "(*mut {:?})", ty),
-                Mutability::Not => write!(fmt, "(*const {:?})", ty),
-            },
-            TyKind::Never => write!(fmt, "Never"),
-            TyKind::Array(ty, const_) => write!(fmt, "[{:?}; {:?}]", ty, const_),
-            TyKind::Closure(id, substitution) => {
-                write!(fmt, "{{closure:{:?}}}<{:?}>", id, substitution)
-            }
-            TyKind::Generator(generator, substitution) => {
-                write!(fmt, "{:?}<{:?}>", generator, substitution)
-            }
-            TyKind::GeneratorWitness(witness, substitution) => {
-                write!(fmt, "{:?}<{:?}>", witness, substitution)
-            }
-            TyKind::Foreign(foreign_ty) => write!(fmt, "{:?}", foreign_ty),
-            TyKind::Error => write!(fmt, "{{error}}"),
-        }
-    }
-}
-
-impl Debug for BoundVar {
-    fn fmt(&self, fmt: &mut Formatter<'_>) -> Result<(), Error> {
-        let BoundVar { debruijn, index } = self;
-        write!(fmt, "{:?}.{:?}", debruijn, index)
-    }
-}
-
-impl Debug for DebruijnIndex {
-    fn fmt(&self, fmt: &mut Formatter<'_>) -> Result<(), Error> {
-        let DebruijnIndex { depth } = self;
-        write!(fmt, "^{}", depth)
-    }
-}
-
-impl<I: Interner> Debug for DynTy<I> {
-    fn fmt(&self, fmt: &mut Formatter<'_>) -> Result<(), Error> {
-        let DynTy { bounds, lifetime } = self;
-        write!(fmt, "dyn {:?} + {:?}", bounds, lifetime)
-    }
-}
-
-impl Debug for InferenceVar {
-    fn fmt(&self, fmt: &mut Formatter<'_>) -> Result<(), Error> {
-        write!(fmt, "?{}", self.index)
-    }
-}
-
-impl<I: Interner> Debug for FnSubst<I> {
-    fn fmt(&self, fmt: &mut Formatter<'_>) -> Result<(), Error> {
-        write!(fmt, "{:?}", self.0)
-    }
-}
-
-impl<I: Interner> Debug for FnPointer<I> {
-    fn fmt(&self, fmt: &mut Formatter<'_>) -> Result<(), Error> {
-        // FIXME -- we should introduce some names or something here
-        let FnPointer {
-            num_binders,
-            substitution,
-            sig,
-        } = self;
-        write!(
-            fmt,
-            "{}{:?} for<{}> {:?}",
-            match sig.safety {
-                Safety::Unsafe => "unsafe ",
-                Safety::Safe => "",
-            },
-            sig.abi,
-            num_binders,
-            substitution
-        )
-    }
-}
-
-impl<I: Interner> Debug for LifetimeData<I> {
-    fn fmt(&self, fmt: &mut Formatter<'_>) -> Result<(), Error> {
-        match self {
-            LifetimeData::BoundVar(db) => write!(fmt, "'{:?}", db),
-            LifetimeData::InferenceVar(var) => write!(fmt, "'{:?}", var),
-            LifetimeData::Placeholder(index) => write!(fmt, "'{:?}", index),
-            LifetimeData::Static => write!(fmt, "'static"),
-            LifetimeData::Erased => write!(fmt, "'<erased>"),
-            LifetimeData::Phantom(..) => unreachable!(),
-        }
-    }
-}
-
-impl<I: Interner> VariableKinds<I> {
-    fn debug(&self) -> VariableKindsDebug<'_, I> {
-        VariableKindsDebug(self)
-    }
-
-    /// Helper method for debugging variable kinds.
-    pub fn inner_debug(&self, interner: I) -> VariableKindsInnerDebug<'_, I> {
-        VariableKindsInnerDebug {
-            variable_kinds: self,
-            interner,
-        }
-    }
-}
-
-struct VariableKindsDebug<'a, I: Interner>(&'a VariableKinds<I>);
-
-impl<'a, I: Interner> Debug for VariableKindsDebug<'a, I> {
-    fn fmt(&self, fmt: &mut Formatter<'_>) -> Result<(), Error> {
-        I::debug_variable_kinds_with_angles(self.0, fmt)
-            .unwrap_or_else(|| write!(fmt, "{:?}", self.0.interned))
-    }
-}
-
-/// Helper struct for showing debug output for `VariableKinds`.
-pub struct VariableKindsInnerDebug<'a, I: Interner> {
-    variable_kinds: &'a VariableKinds<I>,
-    interner: I,
-}
-
-impl<'a, I: Interner> Debug for VariableKindsInnerDebug<'a, I> {
-    fn fmt(&self, fmt: &mut Formatter<'_>) -> Result<(), Error> {
-        // NB: We print variable kinds as a list delimited by `<>`,
-        // like `<K1, K2, ..>`. This is because variable kind lists
-        // are always associated with binders like `forall<type> {
-        // ... }`.
-        write!(fmt, "<")?;
-        for (index, binder) in self.variable_kinds.iter(self.interner).enumerate() {
-            if index > 0 {
-                write!(fmt, ", ")?;
-            }
-            match binder {
-                VariableKind::Ty(TyVariableKind::General) => write!(fmt, "type")?,
-                VariableKind::Ty(TyVariableKind::Integer) => write!(fmt, "integer type")?,
-                VariableKind::Ty(TyVariableKind::Float) => write!(fmt, "float type")?,
-                VariableKind::Lifetime => write!(fmt, "lifetime")?,
-                VariableKind::Const(ty) => write!(fmt, "const: {:?}", ty)?,
-            }
-        }
-        write!(fmt, ">")
-    }
-}
-
-impl<I: Interner> Debug for ConstData<I> {
-    fn fmt(&self, fmt: &mut Formatter<'_>) -> Result<(), Error> {
-        match &self.value {
-            ConstValue::BoundVar(db) => write!(fmt, "{:?}", db),
-            ConstValue::InferenceVar(var) => write!(fmt, "{:?}", var),
-            ConstValue::Placeholder(index) => write!(fmt, "{:?}", index),
-            ConstValue::Concrete(evaluated) => write!(fmt, "{:?}", evaluated),
-        }
-    }
-}
-
-impl<I: Interner> Debug for GoalData<I> {
-    fn fmt(&self, fmt: &mut Formatter<'_>) -> Result<(), Error> {
-        match self {
-            GoalData::Quantified(qkind, ref subgoal) => write!(
-                fmt,
-                "{:?}{:?} {{ {:?} }}",
-                qkind,
-                subgoal.binders.debug(),
-                subgoal.value
-            ),
-            GoalData::Implies(ref wc, ref g) => write!(fmt, "if ({:?}) {{ {:?} }}", wc, g),
-            GoalData::All(ref goals) => write!(fmt, "all{:?}", goals),
-            GoalData::Not(ref g) => write!(fmt, "not {{ {:?} }}", g),
-            GoalData::EqGoal(ref wc) => write!(fmt, "{:?}", wc),
-            GoalData::SubtypeGoal(ref wc) => write!(fmt, "{:?}", wc),
-            GoalData::DomainGoal(ref wc) => write!(fmt, "{:?}", wc),
-            GoalData::CannotProve => write!(fmt, r"¯\_(ツ)_/¯"),
-        }
-    }
-}
-
-/// Helper struct for showing debug output for `Goals`.
-pub struct GoalsDebug<'a, I: Interner> {
-    goals: &'a Goals<I>,
-    interner: I,
-}
-
-impl<'a, I: Interner> Debug for GoalsDebug<'a, I> {
-    fn fmt(&self, fmt: &mut Formatter<'_>) -> Result<(), Error> {
-        write!(fmt, "(")?;
-        for (goal, index) in self.goals.iter(self.interner).zip(0..) {
-            if index > 0 {
-                write!(fmt, ", ")?;
-            }
-            write!(fmt, "{:?}", goal)?;
-        }
-        write!(fmt, ")")?;
-        Ok(())
-    }
-}
-
-impl<I: Interner> Goals<I> {
-    /// Show debug output for `Goals`.
-    pub fn debug(&self, interner: I) -> GoalsDebug<'_, I> {
-        GoalsDebug {
-            goals: self,
-            interner,
-        }
-    }
-}
-
-/// Helper struct for showing debug output for `GenericArgData`.
-pub struct GenericArgDataInnerDebug<'a, I: Interner>(&'a GenericArgData<I>);
-
-impl<'a, I: Interner> Debug for GenericArgDataInnerDebug<'a, I> {
-    fn fmt(&self, fmt: &mut Formatter<'_>) -> Result<(), Error> {
-        match self.0 {
-            GenericArgData::Ty(n) => write!(fmt, "{:?}", n),
-            GenericArgData::Lifetime(n) => write!(fmt, "{:?}", n),
-            GenericArgData::Const(n) => write!(fmt, "{:?}", n),
-        }
-    }
-}
-
-impl<I: Interner> GenericArgData<I> {
-    /// Helper method for debugging `GenericArgData`.
-    pub fn inner_debug(&self) -> GenericArgDataInnerDebug<'_, I> {
-        GenericArgDataInnerDebug(self)
-    }
-}
-
-/// Helper struct for showing debug output for program clause implications.
-pub struct ProgramClauseImplicationDebug<'a, I: Interner> {
-    pci: &'a ProgramClauseImplication<I>,
-    interner: I,
-}
-
-impl<'a, I: Interner> Debug for ProgramClauseImplicationDebug<'a, I> {
-    fn fmt(&self, fmt: &mut Formatter<'_>) -> Result<(), Error> {
-        let ProgramClauseImplicationDebug { pci, interner } = self;
-        write!(fmt, "{:?}", pci.consequence)?;
-
-        let conditions = pci.conditions.as_slice(*interner);
-
-        let conds = conditions.len();
-        if conds == 0 {
-            return Ok(());
-        }
-
-        write!(fmt, " :- ")?;
-        for cond in &conditions[..conds - 1] {
-            write!(fmt, "{:?}, ", cond)?;
-        }
-        write!(fmt, "{:?}", conditions[conds - 1])
-    }
-}
-
-impl<I: Interner> ProgramClauseImplication<I> {
-    /// Show debug output for the program clause implication.
-    pub fn debug(&self, interner: I) -> ProgramClauseImplicationDebug<'_, I> {
-        ProgramClauseImplicationDebug {
-            pci: self,
-            interner,
-        }
-    }
-}
-
-/// Helper struct for showing debug output for application types.
-pub struct TyKindDebug<'a, I: Interner> {
-    ty: &'a TyKind<I>,
-    interner: I,
-}
-
-impl<'a, I: Interner> Debug for TyKindDebug<'a, I> {
-    fn fmt(&self, fmt: &mut Formatter<'_>) -> Result<(), Error> {
-        let interner = self.interner;
-        match self.ty {
-            TyKind::BoundVar(db) => write!(fmt, "{:?}", db),
-            TyKind::Dyn(clauses) => write!(fmt, "{:?}", clauses),
-            TyKind::InferenceVar(var, TyVariableKind::General) => write!(fmt, "{:?}", var),
-            TyKind::InferenceVar(var, TyVariableKind::Integer) => write!(fmt, "{:?}i", var),
-            TyKind::InferenceVar(var, TyVariableKind::Float) => write!(fmt, "{:?}f", var),
-            TyKind::Alias(alias) => write!(fmt, "{:?}", alias),
-            TyKind::Placeholder(index) => write!(fmt, "{:?}", index),
-            TyKind::Function(function) => write!(fmt, "{:?}", function),
-            TyKind::Adt(id, substitution) => {
-                write!(fmt, "{:?}{:?}", id, substitution.with_angle(interner))
-            }
-            TyKind::AssociatedType(assoc_ty, substitution) => {
-                write!(fmt, "{:?}{:?}", assoc_ty, substitution.with_angle(interner))
-            }
-            TyKind::Scalar(scalar) => write!(fmt, "{:?}", scalar),
-            TyKind::Str => write!(fmt, "Str"),
-            TyKind::Tuple(arity, substitution) => {
-                write!(fmt, "{:?}{:?}", arity, substitution.with_angle(interner))
-            }
-            TyKind::OpaqueType(opaque_ty, substitution) => write!(
-                fmt,
-                "!{:?}{:?}",
-                opaque_ty,
-                substitution.with_angle(interner)
-            ),
-            TyKind::Slice(ty) => write!(fmt, "[{:?}]", ty),
-            TyKind::FnDef(fn_def, substitution) => {
-                write!(fmt, "{:?}{:?}", fn_def, substitution.with_angle(interner))
-            }
-            TyKind::Ref(mutability, lifetime, ty) => match mutability {
-                Mutability::Mut => write!(fmt, "(&{:?} mut {:?})", lifetime, ty),
-                Mutability::Not => write!(fmt, "(&{:?} {:?})", lifetime, ty),
-            },
-            TyKind::Raw(mutability, ty) => match mutability {
-                Mutability::Mut => write!(fmt, "(*mut {:?})", ty),
-                Mutability::Not => write!(fmt, "(*const {:?})", ty),
-            },
-            TyKind::Never => write!(fmt, "Never"),
-            TyKind::Array(ty, const_) => write!(fmt, "[{:?}; {:?}]", ty, const_),
-            TyKind::Closure(id, substitution) => write!(
-                fmt,
-                "{{closure:{:?}}}{:?}",
-                id,
-                substitution.with_angle(interner)
-            ),
-            TyKind::Generator(generator, substitution) => write!(
-                fmt,
-                "{:?}{:?}",
-                generator,
-                substitution.with_angle(interner)
-            ),
-            TyKind::GeneratorWitness(witness, substitution) => {
-                write!(fmt, "{:?}{:?}", witness, substitution.with_angle(interner))
-            }
-            TyKind::Foreign(foreign_ty) => write!(fmt, "{:?}", foreign_ty,),
-            TyKind::Error => write!(fmt, "{{error}}"),
-        }
-    }
-}
-
-impl<I: Interner> TyKind<I> {
-    /// Show debug output for the application type.
-    pub fn debug(&self, interner: I) -> TyKindDebug<'_, I> {
-        TyKindDebug { ty: self, interner }
-    }
-}
-
-/// Helper struct for showing debug output for substitutions.
-pub struct SubstitutionDebug<'a, I: Interner> {
-    substitution: &'a Substitution<I>,
-    interner: I,
-}
-
-impl<'a, I: Interner> Debug for SubstitutionDebug<'a, I> {
-    fn fmt(&self, fmt: &mut Formatter<'_>) -> Result<(), Error> {
-        let SubstitutionDebug {
-            substitution,
-            interner,
-        } = self;
-        let mut first = true;
-
-        write!(fmt, "[")?;
-
-        for (index, value) in substitution.iter(*interner).enumerate() {
-            if first {
-                first = false;
-            } else {
-                write!(fmt, ", ")?;
-            }
-
-            write!(fmt, "?{} := {:?}", index, value)?;
-        }
-
-        write!(fmt, "]")?;
-
-        Ok(())
-    }
-}
-
-impl<I: Interner> Substitution<I> {
-    /// Show debug output for the substitution.
-    pub fn debug(&self, interner: I) -> SubstitutionDebug<'_, I> {
-        SubstitutionDebug {
-            substitution: self,
-            interner,
-        }
-    }
-}
-
-impl Debug for PlaceholderIndex {
-    fn fmt(&self, fmt: &mut Formatter<'_>) -> Result<(), Error> {
-        let PlaceholderIndex { ui, idx } = self;
-        write!(fmt, "!{}_{}", ui.counter, idx)
-    }
-}
-
-impl<I: Interner> TraitRef<I> {
-    /// Returns a "Debuggable" type that prints like `P0 as Trait<P1..>`.
-    pub fn with_as(&self) -> impl std::fmt::Debug + '_ {
-        SeparatorTraitRef {
-            trait_ref: self,
-            separator: " as ",
-        }
-    }
-
-    /// Returns a "Debuggable" type that prints like `P0: Trait<P1..>`.
-    pub fn with_colon(&self) -> impl std::fmt::Debug + '_ {
-        SeparatorTraitRef {
-            trait_ref: self,
-            separator: ": ",
-        }
-    }
-}
-
-impl<I: Interner> Debug for TraitRef<I> {
-    fn fmt(&self, fmt: &mut Formatter<'_>) -> Result<(), Error> {
-        Debug::fmt(&self.with_as(), fmt)
-    }
-}
-
-/// Trait ref with associated separator used for debug output.
-pub struct SeparatorTraitRef<'me, I: Interner> {
-    /// The `TraitRef` itself.
-    pub trait_ref: &'me TraitRef<I>,
-
-    /// The separator used for displaying the `TraitRef`.
-    pub separator: &'me str,
-}
-
-/// Helper struct for showing debug output for the `SeperatorTraitRef`.
-pub struct SeparatorTraitRefDebug<'a, 'me, I: Interner> {
-    separator_trait_ref: &'a SeparatorTraitRef<'me, I>,
-    interner: I,
-}
-
-impl<'a, 'me, I: Interner> Debug for SeparatorTraitRefDebug<'a, 'me, I> {
-    fn fmt(&self, fmt: &mut Formatter<'_>) -> Result<(), Error> {
-        let SeparatorTraitRefDebug {
-            separator_trait_ref,
-            interner,
-        } = self;
-        let parameters = separator_trait_ref
-            .trait_ref
-            .substitution
-            .as_slice(*interner);
-        write!(
-            fmt,
-            "{:?}{}{:?}{:?}",
-            parameters[0],
-            separator_trait_ref.separator,
-            separator_trait_ref.trait_ref.trait_id,
-            Angle(&parameters[1..])
-        )
-    }
-}
-
-impl<'me, I: Interner> SeparatorTraitRef<'me, I> {
-    /// Show debug output for the `SeperatorTraitRef`.
-    pub fn debug<'a>(&'a self, interner: I) -> SeparatorTraitRefDebug<'a, 'me, I> {
-        SeparatorTraitRefDebug {
-            separator_trait_ref: self,
-            interner,
-        }
-    }
-}
-
-impl<I: Interner> Debug for LifetimeOutlives<I> {
-    fn fmt(&self, fmt: &mut Formatter<'_>) -> Result<(), Error> {
-        write!(fmt, "{:?}: {:?}", self.a, self.b)
-    }
-}
-
-impl<I: Interner> Debug for TypeOutlives<I> {
-    fn fmt(&self, fmt: &mut Formatter<'_>) -> Result<(), Error> {
-        write!(fmt, "{:?}: {:?}", self.ty, self.lifetime)
-    }
-}
-
-/// Helper struct for showing debug output for projection types.
-pub struct ProjectionTyDebug<'a, I: Interner> {
-    projection_ty: &'a ProjectionTy<I>,
-    interner: I,
-}
-
-impl<'a, I: Interner> Debug for ProjectionTyDebug<'a, I> {
-    fn fmt(&self, fmt: &mut Formatter<'_>) -> Result<(), Error> {
-        let ProjectionTyDebug {
-            projection_ty,
-            interner,
-        } = self;
-        write!(
-            fmt,
-            "({:?}){:?}",
-            projection_ty.associated_ty_id,
-            projection_ty.substitution.with_angle(*interner)
-        )
-    }
-}
-
-impl<I: Interner> ProjectionTy<I> {
-    /// Show debug output for the projection type.
-    pub fn debug(&self, interner: I) -> ProjectionTyDebug<'_, I> {
-        ProjectionTyDebug {
-            projection_ty: self,
-            interner,
-        }
-    }
-}
-
-/// Helper struct for showing debug output for opaque types.
-pub struct OpaqueTyDebug<'a, I: Interner> {
-    opaque_ty: &'a OpaqueTy<I>,
-    interner: I,
-}
-
-impl<'a, I: Interner> Debug for OpaqueTyDebug<'a, I> {
-    fn fmt(&self, fmt: &mut Formatter<'_>) -> Result<(), Error> {
-        let OpaqueTyDebug {
-            opaque_ty,
-            interner,
-        } = self;
-        write!(
-            fmt,
-            "{:?}{:?}",
-            opaque_ty.opaque_ty_id,
-            opaque_ty.substitution.with_angle(*interner)
-        )
-    }
-}
-
-impl<I: Interner> OpaqueTy<I> {
-    /// Show debug output for the opaque type.
-    pub fn debug(&self, interner: I) -> OpaqueTyDebug<'_, I> {
-        OpaqueTyDebug {
-            opaque_ty: self,
-            interner,
-        }
-    }
-}
-
-/// Wraps debug output in angle brackets (`<>`).
-pub struct Angle<'a, T>(pub &'a [T]);
-
-impl<'a, T: Debug> Debug for Angle<'a, T> {
-    fn fmt(&self, fmt: &mut Formatter<'_>) -> Result<(), Error> {
-        if !self.0.is_empty() {
-            write!(fmt, "<")?;
-            for (index, elem) in self.0.iter().enumerate() {
-                if index > 0 {
-                    write!(fmt, ", {:?}", elem)?;
-                } else {
-                    write!(fmt, "{:?}", elem)?;
-                }
-            }
-            write!(fmt, ">")?;
-        }
-        Ok(())
-    }
-}
-
-impl<I: Interner> Debug for Normalize<I> {
-    fn fmt(&self, fmt: &mut Formatter<'_>) -> Result<(), Error> {
-        write!(fmt, "Normalize({:?} -> {:?})", self.alias, self.ty)
-    }
-}
-
-impl<I: Interner> Debug for AliasEq<I> {
-    fn fmt(&self, fmt: &mut Formatter<'_>) -> Result<(), Error> {
-        write!(fmt, "AliasEq({:?} = {:?})", self.alias, self.ty)
-    }
-}
-
-impl<I: Interner> Debug for WhereClause<I> {
-    fn fmt(&self, fmt: &mut Formatter<'_>) -> Result<(), Error> {
-        match self {
-            WhereClause::Implemented(tr) => write!(fmt, "Implemented({:?})", tr.with_colon()),
-            WhereClause::AliasEq(a) => write!(fmt, "{:?}", a),
-            WhereClause::LifetimeOutlives(l_o) => write!(fmt, "{:?}", l_o),
-            WhereClause::TypeOutlives(t_o) => write!(fmt, "{:?}", t_o),
-        }
-    }
-}
-
-impl<I: Interner> Debug for FromEnv<I> {
-    fn fmt(&self, fmt: &mut Formatter<'_>) -> Result<(), Error> {
-        match self {
-            FromEnv::Trait(t) => write!(fmt, "FromEnv({:?})", t.with_colon()),
-            FromEnv::Ty(t) => write!(fmt, "FromEnv({:?})", t),
-        }
-    }
-}
-
-impl<I: Interner> Debug for WellFormed<I> {
-    fn fmt(&self, fmt: &mut Formatter<'_>) -> Result<(), Error> {
-        match self {
-            WellFormed::Trait(t) => write!(fmt, "WellFormed({:?})", t.with_colon()),
-            WellFormed::Ty(t) => write!(fmt, "WellFormed({:?})", t),
-        }
-    }
-}
-
-impl<I: Interner> Debug for DomainGoal<I> {
-    fn fmt(&self, fmt: &mut Formatter<'_>) -> Result<(), Error> {
-        match self {
-            DomainGoal::Holds(n) => write!(fmt, "{:?}", n),
-            DomainGoal::WellFormed(n) => write!(fmt, "{:?}", n),
-            DomainGoal::FromEnv(n) => write!(fmt, "{:?}", n),
-            DomainGoal::Normalize(n) => write!(fmt, "{:?}", n),
-            DomainGoal::IsLocal(n) => write!(fmt, "IsLocal({:?})", n),
-            DomainGoal::IsUpstream(n) => write!(fmt, "IsUpstream({:?})", n),
-            DomainGoal::IsFullyVisible(n) => write!(fmt, "IsFullyVisible({:?})", n),
-            DomainGoal::LocalImplAllowed(tr) => {
-                write!(fmt, "LocalImplAllowed({:?})", tr.with_colon(),)
-            }
-            DomainGoal::Compatible => write!(fmt, "Compatible"),
-            DomainGoal::DownstreamType(n) => write!(fmt, "DownstreamType({:?})", n),
-            DomainGoal::Reveal => write!(fmt, "Reveal"),
-            DomainGoal::ObjectSafe(n) => write!(fmt, "ObjectSafe({:?})", n),
-        }
-    }
-}
-
-impl<I: Interner> Debug for EqGoal<I> {
-    fn fmt(&self, fmt: &mut Formatter<'_>) -> Result<(), Error> {
-        write!(fmt, "({:?} = {:?})", self.a, self.b)
-    }
-}
-
-impl<I: Interner> Debug for SubtypeGoal<I> {
-    fn fmt(&self, fmt: &mut Formatter<'_>) -> Result<(), Error> {
-        write!(fmt, "({:?} <: {:?})", self.a, self.b)
-    }
-}
-
-impl<T: HasInterner + Debug> Debug for Binders<T> {
-    fn fmt(&self, fmt: &mut Formatter<'_>) -> Result<(), Error> {
-        let Binders {
-            ref binders,
-            ref value,
-        } = *self;
-        write!(fmt, "for{:?} ", binders.debug())?;
-        Debug::fmt(value, fmt)
-    }
-}
-
-impl<I: Interner> Debug for ProgramClauseData<I> {
-    fn fmt(&self, fmt: &mut Formatter<'_>) -> Result<(), Error> {
-        write!(fmt, "{:?}", self.0)
-    }
-}
-
-impl<I: Interner> Debug for Environment<I> {
-    fn fmt(&self, fmt: &mut Formatter<'_>) -> Result<(), Error> {
-        write!(fmt, "Env({:?})", self.clauses)
-    }
-}
-
-impl<I: Interner> Debug for CanonicalVarKinds<I> {
-    fn fmt(&self, fmt: &mut Formatter<'_>) -> Result<(), Error> {
-        I::debug_canonical_var_kinds(self, fmt)
-            .unwrap_or_else(|| write!(fmt, "{:?}", self.interned))
-    }
-}
-
-impl<T: HasInterner + Display> Canonical<T> {
-    /// Display the canonicalized item.
-    pub fn display(&self, interner: T::Interner) -> CanonicalDisplay<'_, T> {
-        CanonicalDisplay {
-            canonical: self,
-            interner,
-        }
-    }
-}
-
-/// Helper struct for displaying canonicalized items.
-pub struct CanonicalDisplay<'a, T: HasInterner> {
-    canonical: &'a Canonical<T>,
-    interner: T::Interner,
-}
-
-impl<'a, T: HasInterner + Display> Display for CanonicalDisplay<'a, T> {
-    fn fmt(&self, f: &mut Formatter<'_>) -> Result<(), Error> {
-        let Canonical { binders, value } = self.canonical;
-        let interner = self.interner;
-        let binders = binders.as_slice(interner);
-        if binders.is_empty() {
-            // Ordinarily, we try to print all binder levels, if they
-            // are empty, but we can skip in this *particular* case
-            // because we know that `Canonical` terms are never
-            // supposed to contain free variables.  In other words,
-            // all "bound variables" that appear inside the canonical
-            // value must reference values that appear in `binders`.
-            write!(f, "{}", value)?;
-        } else {
-            write!(f, "for<")?;
-
-            for (i, pk) in binders.iter().enumerate() {
-                if i > 0 {
-                    write!(f, ",")?;
-                }
-                write!(f, "?{}", pk.skip_kind())?;
-            }
-
-            write!(f, "> {{ {} }}", value)?;
-        }
-
-        Ok(())
-    }
-}
-
-impl<I: Interner> Debug for GenericArgData<I> {
-    fn fmt(&self, fmt: &mut Formatter<'_>) -> Result<(), Error> {
-        match self {
-            GenericArgData::Ty(t) => write!(fmt, "Ty({:?})", t),
-            GenericArgData::Lifetime(l) => write!(fmt, "Lifetime({:?})", l),
-            GenericArgData::Const(c) => write!(fmt, "Const({:?})", c),
-        }
-    }
-}
-
-impl<I: Interner> Debug for VariableKind<I> {
-    fn fmt(&self, fmt: &mut Formatter<'_>) -> Result<(), Error> {
-        match self {
-            VariableKind::Ty(TyVariableKind::General) => write!(fmt, "type"),
-            VariableKind::Ty(TyVariableKind::Integer) => write!(fmt, "integer type"),
-            VariableKind::Ty(TyVariableKind::Float) => write!(fmt, "float type"),
-            VariableKind::Lifetime => write!(fmt, "lifetime"),
-            VariableKind::Const(ty) => write!(fmt, "const: {:?}", ty),
-        }
-    }
-}
-
-impl<I: Interner, T: Debug> Debug for WithKind<I, T> {
-    fn fmt(&self, fmt: &mut Formatter<'_>) -> Result<(), Error> {
-        let value = self.skip_kind();
-        match &self.kind {
-            VariableKind::Ty(TyVariableKind::General) => write!(fmt, "{:?} with kind type", value),
-            VariableKind::Ty(TyVariableKind::Integer) => {
-                write!(fmt, "{:?} with kind integer type", value)
-            }
-            VariableKind::Ty(TyVariableKind::Float) => {
-                write!(fmt, "{:?} with kind float type", value)
-            }
-            VariableKind::Lifetime => write!(fmt, "{:?} with kind lifetime", value),
-            VariableKind::Const(ty) => write!(fmt, "{:?} with kind {:?}", value, ty),
-        }
-    }
-}
-
-impl<I: Interner> Debug for Constraint<I> {
-    fn fmt(&self, fmt: &mut Formatter<'_>) -> Result<(), Error> {
-        match self {
-            Constraint::LifetimeOutlives(a, b) => write!(fmt, "{:?}: {:?}", a, b),
-            Constraint::TypeOutlives(ty, lifetime) => write!(fmt, "{:?}: {:?}", ty, lifetime),
-        }
-    }
-}
-
-impl<I: Interner> Display for ConstrainedSubst<I> {
-    #[rustfmt::skip]
-    fn fmt(&self, f: &mut Formatter<'_>) -> Result<(), Error> {
-        let ConstrainedSubst { subst, constraints } = self;
-
-        let mut first = true;
-
-        let subst = format!("{}", Fmt(|f| Display::fmt(subst, f)));
-        if subst != "[]" {
-            write!(f, "substitution {}", subst)?;
-            first = false;
-        }
-
-        let constraints = format!("{}", Fmt(|f| Debug::fmt(constraints, f)));
-        if constraints != "[]" {
-            if !first { write!(f, ", ")?; }
-            write!(f, "lifetime constraints {}", constraints)?;
-            first = false;
-        }
-
-        let _ = first;
-        Ok(())
-    }
-}
-
-impl<I: Interner> Substitution<I> {
-    /// Displays the substitution in the form `< P0, .. Pn >`, or (if
-    /// the substitution is empty) as an empty string.
-    pub fn with_angle(&self, interner: I) -> Angle<'_, GenericArg<I>> {
-        Angle(self.as_slice(interner))
-    }
-}
-
-impl<I: Interner> Debug for Substitution<I> {
-    fn fmt(&self, fmt: &mut Formatter<'_>) -> Result<(), Error> {
-        Display::fmt(self, fmt)
-    }
-}
-
-impl<I: Interner> Debug for Variances<I> {
-    fn fmt(&self, fmt: &mut Formatter<'_>) -> Result<(), Error> {
-        I::debug_variances(self, fmt).unwrap_or_else(|| write!(fmt, "{:?}", self.interned))
-    }
-}
diff --git a/vendor/chalk-ir/src/fold.rs b/vendor/chalk-ir/src/fold.rs
deleted file mode 100644
index b15cbff7a..000000000
--- a/vendor/chalk-ir/src/fold.rs
+++ /dev/null
@@ -1,920 +0,0 @@
-//! Traits for transforming bits of IR.
-
-use crate::*;
-use std::convert::Infallible;
-use std::fmt::Debug;
-
-mod binder_impls;
-mod boring_impls;
-mod in_place;
-pub mod shift;
-mod subst;
-
-pub use self::shift::Shift;
-pub use self::subst::Subst;
-
-/// A "folder" is a transformer that can be used to make a copy of
-/// some term -- that is, some bit of IR, such as a `Goal` -- with
-/// certain changes applied. The idea is that it contains methods that
-/// let you swap types/lifetimes for new types/lifetimes; meanwhile,
-/// each bit of IR implements the `TypeFoldable` trait which, given a
-/// `FallibleTypeFolder`, will reconstruct itself, invoking the folder's
-/// methods to transform each of the types/lifetimes embedded within.
-///
-/// As the name suggests, folds performed by `FallibleTypeFolder` can
-/// fail (with type `Error`); if the folder cannot fail, consider
-/// implementing `TypeFolder` instead (which is an infallible, but
-/// otherwise equivalent, trait).
-///
-/// # Usage patterns
-///
-/// ## Substituting for free variables
-///
-/// Most of the time, though, we are not interested in adjust
-/// arbitrary types/lifetimes, but rather just free variables (even
-/// more often, just free existential variables) that appear within
-/// the term.
-///
-/// For this reason, the `FallibleTypeFolder` trait extends two other
-/// traits that contain methods that are invoked when just those particular
-///
-/// In particular, folders can intercept references to free variables
-/// (either existentially or universally quantified) and replace them
-/// with other types/lifetimes as appropriate.
-///
-/// To create a folder `F`, one never implements `FallibleTypeFolder`
-/// directly, but instead implements one of each of these three sub-traits:
-///
-/// - `FreeVarFolder` -- folds `BoundVar` instances that appear free
-///   in the term being folded (use `DefaultFreeVarFolder` to
-///   ignore/forbid these altogether)
-/// - `InferenceFolder` -- folds existential `InferenceVar` instances
-///   that appear in the term being folded (use
-///   `DefaultInferenceFolder` to ignore/forbid these altogether)
-/// - `PlaceholderFolder` -- folds universal `Placeholder` instances
-///   that appear in the term being folded (use
-///   `DefaultPlaceholderFolder` to ignore/forbid these altogether)
-///
-/// To **apply** a folder, use the `TypeFoldable::try_fold_with` method,
-/// like so
-///
-/// ```rust,ignore
-/// let x = x.try_fold_with(&mut folder, 0);
-/// ```
-pub trait FallibleTypeFolder<I: Interner> {
-    /// The type this folder returns when folding fails. This is
-    /// commonly [`NoSolution`].
-    type Error;
-
-    /// Creates a `dyn` value from this folder. Unfortunately, this
-    /// must be added manually to each impl of FallibleTypeFolder; it
-    /// permits the default implements below to create a
-    /// `&mut dyn FallibleTypeFolder` from `Self` without knowing what
-    /// `Self` is (by invoking this method). Effectively, this limits
-    /// impls of `FallibleTypeFolder` to types for which we are able to
-    /// create a dyn value (i.e., not `[T]` types).
-    fn as_dyn(&mut self) -> &mut dyn FallibleTypeFolder<I, Error = Self::Error>;
-
-    /// Top-level callback: invoked for each `Ty<I>` that is
-    /// encountered when folding. By default, invokes
-    /// `try_super_fold_with`, which will in turn invoke the more
-    /// specialized folding methods below, like `try_fold_free_var_ty`.
-    fn try_fold_ty(
-        &mut self,
-        ty: Ty<I>,
-        outer_binder: DebruijnIndex,
-    ) -> Result<Ty<I>, Self::Error> {
-        ty.try_super_fold_with(self.as_dyn(), outer_binder)
-    }
-
-    /// Top-level callback: invoked for each `Lifetime<I>` that is
-    /// encountered when folding. By default, invokes
-    /// `try_super_fold_with`, which will in turn invoke the more
-    /// specialized folding methods below, like `try_fold_free_var_lifetime`.
-    fn try_fold_lifetime(
-        &mut self,
-        lifetime: Lifetime<I>,
-        outer_binder: DebruijnIndex,
-    ) -> Result<Lifetime<I>, Self::Error> {
-        lifetime.try_super_fold_with(self.as_dyn(), outer_binder)
-    }
-
-    /// Top-level callback: invoked for each `Const<I>` that is
-    /// encountered when folding. By default, invokes
-    /// `try_super_fold_with`, which will in turn invoke the more
-    /// specialized folding methods below, like `try_fold_free_var_const`.
-    fn try_fold_const(
-        &mut self,
-        constant: Const<I>,
-        outer_binder: DebruijnIndex,
-    ) -> Result<Const<I>, Self::Error> {
-        constant.try_super_fold_with(self.as_dyn(), outer_binder)
-    }
-
-    /// Invoked for every program clause. By default, recursively folds the goals contents.
-    fn try_fold_program_clause(
-        &mut self,
-        clause: ProgramClause<I>,
-        outer_binder: DebruijnIndex,
-    ) -> Result<ProgramClause<I>, Self::Error> {
-        clause.try_super_fold_with(self.as_dyn(), outer_binder)
-    }
-
-    /// Invoked for every goal. By default, recursively folds the goals contents.
-    fn try_fold_goal(
-        &mut self,
-        goal: Goal<I>,
-        outer_binder: DebruijnIndex,
-    ) -> Result<Goal<I>, Self::Error> {
-        goal.try_super_fold_with(self.as_dyn(), outer_binder)
-    }
-
-    /// If overridden to return true, then folding will panic if a
-    /// free variable is encountered. This should be done if free
-    /// type/lifetime variables are not expected.
-    fn forbid_free_vars(&self) -> bool {
-        false
-    }
-
-    /// Invoked for `TyKind::BoundVar` instances that are not bound
-    /// within the type being folded over:
-    ///
-    /// - `depth` is the depth of the `TyKind::BoundVar`; this has
-    ///   been adjusted to account for binders in scope.
-    /// - `binders` is the number of binders in scope.
-    ///
-    /// This should return a type suitable for a context with
-    /// `binders` in scope.
-    fn try_fold_free_var_ty(
-        &mut self,
-        bound_var: BoundVar,
-        outer_binder: DebruijnIndex,
-    ) -> Result<Ty<I>, Self::Error> {
-        if self.forbid_free_vars() {
-            panic!(
-                "unexpected free variable with depth `{:?}` with outer binder {:?}",
-                bound_var, outer_binder
-            )
-        } else {
-            let bound_var = bound_var.shifted_in_from(outer_binder);
-            Ok(TyKind::<I>::BoundVar(bound_var).intern(self.interner()))
-        }
-    }
-
-    /// As `try_fold_free_var_ty`, but for lifetimes.
-    fn try_fold_free_var_lifetime(
-        &mut self,
-        bound_var: BoundVar,
-        outer_binder: DebruijnIndex,
-    ) -> Result<Lifetime<I>, Self::Error> {
-        if self.forbid_free_vars() {
-            panic!(
-                "unexpected free variable with depth `{:?}` with outer binder {:?}",
-                bound_var, outer_binder
-            )
-        } else {
-            let bound_var = bound_var.shifted_in_from(outer_binder);
-            Ok(LifetimeData::<I>::BoundVar(bound_var).intern(self.interner()))
-        }
-    }
-
-    /// As `try_fold_free_var_ty`, but for constants.
-    fn try_fold_free_var_const(
-        &mut self,
-        ty: Ty<I>,
-        bound_var: BoundVar,
-        outer_binder: DebruijnIndex,
-    ) -> Result<Const<I>, Self::Error> {
-        if self.forbid_free_vars() {
-            panic!(
-                "unexpected free variable with depth `{:?}` with outer binder {:?}",
-                bound_var, outer_binder
-            )
-        } else {
-            let bound_var = bound_var.shifted_in_from(outer_binder);
-            Ok(ConstData {
-                ty: ty.try_fold_with(self.as_dyn(), outer_binder)?,
-                value: ConstValue::<I>::BoundVar(bound_var),
-            }
-            .intern(self.interner()))
-        }
-    }
-
-    /// If overridden to return true, we will panic when a free
-    /// placeholder type/lifetime/const 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. Returns a type
-    /// to use instead, which should be suitably shifted to account
-    /// for `binders`.
-    ///
-    /// - `universe` is the universe of the `TypeName::ForAll` that was found
-    /// - `binders` is the number of binders in scope
-    #[allow(unused_variables)]
-    fn try_fold_free_placeholder_ty(
-        &mut self,
-        universe: PlaceholderIndex,
-        outer_binder: DebruijnIndex,
-    ) -> Result<Ty<I>, Self::Error> {
-        if self.forbid_free_placeholders() {
-            panic!("unexpected placeholder type `{:?}`", universe)
-        } else {
-            Ok(universe.to_ty::<I>(self.interner()))
-        }
-    }
-
-    /// As with `try_fold_free_placeholder_ty`, but for lifetimes.
-    #[allow(unused_variables)]
-    fn try_fold_free_placeholder_lifetime(
-        &mut self,
-        universe: PlaceholderIndex,
-        outer_binder: DebruijnIndex,
-    ) -> Result<Lifetime<I>, Self::Error> {
-        if self.forbid_free_placeholders() {
-            panic!("unexpected placeholder lifetime `{:?}`", universe)
-        } else {
-            Ok(universe.to_lifetime(self.interner()))
-        }
-    }
-
-    /// As with `try_fold_free_placeholder_ty`, but for constants.
-    #[allow(unused_variables)]
-    fn try_fold_free_placeholder_const(
-        &mut self,
-        ty: Ty<I>,
-        universe: PlaceholderIndex,
-        outer_binder: DebruijnIndex,
-    ) -> Result<Const<I>, Self::Error> {
-        if self.forbid_free_placeholders() {
-            panic!("unexpected placeholder const `{:?}`", universe)
-        } else {
-            Ok(universe.to_const(
-                self.interner(),
-                ty.try_fold_with(self.as_dyn(), outer_binder)?,
-            ))
-        }
-    }
-
-    /// If overridden to return true, inference variables will trigger
-    /// panics when folded. 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. Returns a type
-    /// to use instead, which should be suitably shifted to account
-    /// for `binders`.
-    ///
-    /// - `universe` is the universe of the `TypeName::ForAll` that was found
-    /// - `binders` is the number of binders in scope
-    #[allow(unused_variables)]
-    fn try_fold_inference_ty(
-        &mut self,
-        var: InferenceVar,
-        kind: TyVariableKind,
-        outer_binder: DebruijnIndex,
-    ) -> Result<Ty<I>, Self::Error> {
-        if self.forbid_inference_vars() {
-            panic!("unexpected inference type `{:?}`", var)
-        } else {
-            Ok(var.to_ty(self.interner(), kind))
-        }
-    }
-
-    /// As with `try_fold_inference_ty`, but for lifetimes.
-    #[allow(unused_variables)]
-    fn try_fold_inference_lifetime(
-        &mut self,
-        var: InferenceVar,
-        outer_binder: DebruijnIndex,
-    ) -> Result<Lifetime<I>, Self::Error> {
-        if self.forbid_inference_vars() {
-            panic!("unexpected inference lifetime `'{:?}`", var)
-        } else {
-            Ok(var.to_lifetime(self.interner()))
-        }
-    }
-
-    /// As with `try_fold_inference_ty`, but for constants.
-    #[allow(unused_variables)]
-    fn try_fold_inference_const(
-        &mut self,
-        ty: Ty<I>,
-        var: InferenceVar,
-        outer_binder: DebruijnIndex,
-    ) -> Result<Const<I>, Self::Error> {
-        if self.forbid_inference_vars() {
-            panic!("unexpected inference const `{:?}`", var)
-        } else {
-            Ok(var.to_const(
-                self.interner(),
-                ty.try_fold_with(self.as_dyn(), outer_binder)?,
-            ))
-        }
-    }
-
-    /// Gets the interner that is being folded from.
-    fn interner(&self) -> I;
-}
-
-/// A "folder" is a transformer that can be used to make a copy of
-/// some term -- that is, some bit of IR, such as a `Goal` -- with
-/// certain changes applied. The idea is that it contains methods that
-/// let you swap types/lifetimes for new types/lifetimes; meanwhile,
-/// each bit of IR implements the `TypeFoldable` trait which, given a
-/// `TypeFolder`, will reconstruct itself, invoking the folder's methods
-/// to transform each of the types/lifetimes embedded within.
-///
-/// Folds performed by `TypeFolder` cannot fail.  If folds might fail,
-/// consider implementing `FallibleTypeFolder` instead (which is a
-/// fallible, but otherwise equivalent, trait).
-///
-/// # Usage patterns
-///
-/// ## Substituting for free variables
-///
-/// Most of the time, though, we are not interested in adjust
-/// arbitrary types/lifetimes, but rather just free variables (even
-/// more often, just free existential variables) that appear within
-/// the term.
-///
-/// For this reason, the `TypeFolder` trait extends two other traits that
-/// contain methods that are invoked when just those particular
-///
-/// In particular, folders can intercept references to free variables
-/// (either existentially or universally quantified) and replace them
-/// with other types/lifetimes as appropriate.
-///
-/// To create a folder `F`, one never implements `TypeFolder` directly, but instead
-/// implements one of each of these three sub-traits:
-///
-/// - `FreeVarFolder` -- folds `BoundVar` instances that appear free
-///   in the term being folded (use `DefaultFreeVarFolder` to
-///   ignore/forbid these altogether)
-/// - `InferenceFolder` -- folds existential `InferenceVar` instances
-///   that appear in the term being folded (use
-///   `DefaultInferenceFolder` to ignore/forbid these altogether)
-/// - `PlaceholderFolder` -- folds universal `Placeholder` instances
-///   that appear in the term being folded (use
-///   `DefaultPlaceholderFolder` to ignore/forbid these altogether)
-///
-/// To **apply** a folder, use the `TypeFoldable::fold_with` method, like so
-///
-/// ```rust,ignore
-/// let x = x.fold_with(&mut folder, 0);
-/// ```
-pub trait TypeFolder<I: Interner>: FallibleTypeFolder<I, Error = Infallible> {
-    /// Creates a `dyn` value from this folder. Unfortunately, this
-    /// must be added manually to each impl of TypeFolder; it permits the
-    /// default implements below to create a `&mut dyn TypeFolder` from
-    /// `Self` without knowing what `Self` is (by invoking this
-    /// method). Effectively, this limits impls of `TypeFolder` to types
-    /// for which we are able to create a dyn value (i.e., not `[T]`
-    /// types).
-    fn as_dyn(&mut self) -> &mut dyn TypeFolder<I>;
-
-    /// Top-level callback: invoked for each `Ty<I>` that is
-    /// encountered when folding. By default, invokes
-    /// `super_fold_with`, which will in turn invoke the more
-    /// specialized folding methods below, like `fold_free_var_ty`.
-    fn fold_ty(&mut self, ty: Ty<I>, outer_binder: DebruijnIndex) -> Ty<I> {
-        ty.super_fold_with(TypeFolder::as_dyn(self), outer_binder)
-    }
-
-    /// Top-level callback: invoked for each `Lifetime<I>` that is
-    /// encountered when folding. By default, invokes
-    /// `super_fold_with`, which will in turn invoke the more
-    /// specialized folding methods below, like `fold_free_var_lifetime`.
-    fn fold_lifetime(&mut self, lifetime: Lifetime<I>, outer_binder: DebruijnIndex) -> Lifetime<I> {
-        lifetime.super_fold_with(TypeFolder::as_dyn(self), outer_binder)
-    }
-
-    /// Top-level callback: invoked for each `Const<I>` that is
-    /// encountered when folding. By default, invokes
-    /// `super_fold_with`, which will in turn invoke the more
-    /// specialized folding methods below, like `fold_free_var_const`.
-    fn fold_const(&mut self, constant: Const<I>, outer_binder: DebruijnIndex) -> Const<I> {
-        constant.super_fold_with(TypeFolder::as_dyn(self), outer_binder)
-    }
-
-    /// Invoked for every program clause. By default, recursively folds the goals contents.
-    fn fold_program_clause(
-        &mut self,
-        clause: ProgramClause<I>,
-        outer_binder: DebruijnIndex,
-    ) -> ProgramClause<I> {
-        clause.super_fold_with(TypeFolder::as_dyn(self), outer_binder)
-    }
-
-    /// Invoked for every goal. By default, recursively folds the goals contents.
-    fn fold_goal(&mut self, goal: Goal<I>, outer_binder: DebruijnIndex) -> Goal<I> {
-        goal.super_fold_with(TypeFolder::as_dyn(self), outer_binder)
-    }
-
-    /// If overridden to return true, then folding will panic if a
-    /// free variable is encountered. This should be done if free
-    /// type/lifetime variables are not expected.
-    fn forbid_free_vars(&self) -> bool {
-        false
-    }
-
-    /// Invoked for `TyKind::BoundVar` instances that are not bound
-    /// within the type being folded over:
-    ///
-    /// - `depth` is the depth of the `TyKind::BoundVar`; this has
-    ///   been adjusted to account for binders in scope.
-    /// - `binders` is the number of binders in scope.
-    ///
-    /// This should return a type suitable for a context with
-    /// `binders` in scope.
-    fn fold_free_var_ty(&mut self, bound_var: BoundVar, outer_binder: DebruijnIndex) -> Ty<I> {
-        if TypeFolder::forbid_free_vars(self) {
-            panic!(
-                "unexpected free variable with depth `{:?}` with outer binder {:?}",
-                bound_var, outer_binder
-            )
-        } else {
-            let bound_var = bound_var.shifted_in_from(outer_binder);
-            TyKind::<I>::BoundVar(bound_var).intern(TypeFolder::interner(self))
-        }
-    }
-
-    /// As `fold_free_var_ty`, but for lifetimes.
-    fn fold_free_var_lifetime(
-        &mut self,
-        bound_var: BoundVar,
-        outer_binder: DebruijnIndex,
-    ) -> Lifetime<I> {
-        if TypeFolder::forbid_free_vars(self) {
-            panic!(
-                "unexpected free variable with depth `{:?}` with outer binder {:?}",
-                bound_var, outer_binder
-            )
-        } else {
-            let bound_var = bound_var.shifted_in_from(outer_binder);
-            LifetimeData::<I>::BoundVar(bound_var).intern(TypeFolder::interner(self))
-        }
-    }
-
-    /// As `fold_free_var_ty`, but for constants.
-    fn fold_free_var_const(
-        &mut self,
-        ty: Ty<I>,
-        bound_var: BoundVar,
-        outer_binder: DebruijnIndex,
-    ) -> Const<I> {
-        if TypeFolder::forbid_free_vars(self) {
-            panic!(
-                "unexpected free variable with depth `{:?}` with outer binder {:?}",
-                bound_var, outer_binder
-            )
-        } else {
-            let bound_var = bound_var.shifted_in_from(outer_binder);
-            ConstData {
-                ty: ty.fold_with(TypeFolder::as_dyn(self), outer_binder),
-                value: ConstValue::<I>::BoundVar(bound_var),
-            }
-            .intern(TypeFolder::interner(self))
-        }
-    }
-
-    /// If overridden to return true, we will panic when a free
-    /// placeholder type/lifetime/const 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. Returns a type
-    /// to use instead, which should be suitably shifted to account
-    /// for `binders`.
-    ///
-    /// - `universe` is the universe of the `TypeName::ForAll` that was found
-    /// - `binders` is the number of binders in scope
-    #[allow(unused_variables)]
-    fn fold_free_placeholder_ty(
-        &mut self,
-        universe: PlaceholderIndex,
-        outer_binder: DebruijnIndex,
-    ) -> Ty<I> {
-        if TypeFolder::forbid_free_placeholders(self) {
-            panic!("unexpected placeholder type `{:?}`", universe)
-        } else {
-            universe.to_ty::<I>(TypeFolder::interner(self))
-        }
-    }
-
-    /// As with `fold_free_placeholder_ty`, but for lifetimes.
-    #[allow(unused_variables)]
-    fn fold_free_placeholder_lifetime(
-        &mut self,
-        universe: PlaceholderIndex,
-        outer_binder: DebruijnIndex,
-    ) -> Lifetime<I> {
-        if TypeFolder::forbid_free_placeholders(self) {
-            panic!("unexpected placeholder lifetime `{:?}`", universe)
-        } else {
-            universe.to_lifetime(TypeFolder::interner(self))
-        }
-    }
-
-    /// As with `fold_free_placeholder_ty`, but for constants.
-    #[allow(unused_variables)]
-    fn fold_free_placeholder_const(
-        &mut self,
-        ty: Ty<I>,
-        universe: PlaceholderIndex,
-        outer_binder: DebruijnIndex,
-    ) -> Const<I> {
-        if TypeFolder::forbid_free_placeholders(self) {
-            panic!("unexpected placeholder const `{:?}`", universe)
-        } else {
-            universe.to_const(
-                TypeFolder::interner(self),
-                ty.fold_with(TypeFolder::as_dyn(self), outer_binder),
-            )
-        }
-    }
-
-    /// If overridden to return true, inference variables will trigger
-    /// panics when folded. 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. Returns a type
-    /// to use instead, which should be suitably shifted to account
-    /// for `binders`.
-    ///
-    /// - `universe` is the universe of the `TypeName::ForAll` that was found
-    /// - `binders` is the number of binders in scope
-    #[allow(unused_variables)]
-    fn fold_inference_ty(
-        &mut self,
-        var: InferenceVar,
-        kind: TyVariableKind,
-        outer_binder: DebruijnIndex,
-    ) -> Ty<I> {
-        if TypeFolder::forbid_inference_vars(self) {
-            panic!("unexpected inference type `{:?}`", var)
-        } else {
-            var.to_ty(TypeFolder::interner(self), kind)
-        }
-    }
-
-    /// As with `fold_inference_ty`, but for lifetimes.
-    #[allow(unused_variables)]
-    fn fold_inference_lifetime(
-        &mut self,
-        var: InferenceVar,
-        outer_binder: DebruijnIndex,
-    ) -> Lifetime<I> {
-        if TypeFolder::forbid_inference_vars(self) {
-            panic!("unexpected inference lifetime `'{:?}`", var)
-        } else {
-            var.to_lifetime(TypeFolder::interner(self))
-        }
-    }
-
-    /// As with `fold_inference_ty`, but for constants.
-    #[allow(unused_variables)]
-    fn fold_inference_const(
-        &mut self,
-        ty: Ty<I>,
-        var: InferenceVar,
-        outer_binder: DebruijnIndex,
-    ) -> Const<I> {
-        if TypeFolder::forbid_inference_vars(self) {
-            panic!("unexpected inference const `{:?}`", var)
-        } else {
-            var.to_const(
-                TypeFolder::interner(self),
-                ty.fold_with(TypeFolder::as_dyn(self), outer_binder),
-            )
-        }
-    }
-
-    /// Gets the interner that is being folded from.
-    fn interner(&self) -> I;
-}
-
-/// Applies the given `TypeFolder` to a value, producing a folded result
-/// of type `Self::Result`. The result type is typically the same as
-/// the source type, but in some cases we convert from borrowed
-/// to owned as well (e.g., the folder for `&T` will fold to a fresh
-/// `T`; well, actually `T::Result`).
-pub trait TypeFoldable<I: Interner>: Debug + Sized {
-    /// Apply the given folder `folder` to `self`; `binders` is the
-    /// number of binders that are in scope when beginning the
-    /// folder. Typically `binders` starts as 0, but is adjusted when
-    /// we encounter `Binders<T>` in the IR or other similar
-    /// constructs.
-    fn try_fold_with<E>(
-        self,
-        folder: &mut dyn FallibleTypeFolder<I, Error = E>,
-        outer_binder: DebruijnIndex,
-    ) -> Result<Self, E>;
-
-    /// A convenient alternative to `try_fold_with` for use with infallible
-    /// folders. Do not override this method, to ensure coherence with
-    /// `try_fold_with`.
-    fn fold_with(self, folder: &mut dyn TypeFolder<I>, outer_binder: DebruijnIndex) -> Self {
-        self.try_fold_with(FallibleTypeFolder::as_dyn(folder), outer_binder)
-            .unwrap()
-    }
-}
-
-/// For types where "fold" invokes a callback on the `TypeFolder`, the
-/// `TypeSuperFoldable` trait captures the recursive behavior that folds all
-/// the contents of the type.
-pub trait TypeSuperFoldable<I: Interner>: TypeFoldable<I> {
-    /// Recursively folds the value.
-    fn try_super_fold_with<E>(
-        self,
-        folder: &mut dyn FallibleTypeFolder<I, Error = E>,
-        outer_binder: DebruijnIndex,
-    ) -> Result<Self, E>;
-
-    /// A convenient alternative to `try_super_fold_with` for use with
-    /// infallible folders. Do not override this method, to ensure coherence
-    /// with `try_super_fold_with`.
-    fn super_fold_with(self, folder: &mut dyn TypeFolder<I>, outer_binder: DebruijnIndex) -> Self {
-        self.try_super_fold_with(FallibleTypeFolder::as_dyn(folder), outer_binder)
-            .unwrap()
-    }
-}
-
-/// "Folding" a type invokes the `try_fold_ty` method on the folder; this
-/// usually (in turn) invokes `try_super_fold_ty` to fold the individual
-/// parts.
-impl<I: Interner> TypeFoldable<I> for Ty<I> {
-    fn try_fold_with<E>(
-        self,
-        folder: &mut dyn FallibleTypeFolder<I, Error = E>,
-        outer_binder: DebruijnIndex,
-    ) -> Result<Self, E> {
-        folder.try_fold_ty(self, outer_binder)
-    }
-}
-
-/// "Super fold" for a type invokes te more detailed callbacks on the type
-impl<I> TypeSuperFoldable<I> for Ty<I>
-where
-    I: Interner,
-{
-    fn try_super_fold_with<E>(
-        self,
-        folder: &mut dyn FallibleTypeFolder<I, Error = E>,
-        outer_binder: DebruijnIndex,
-    ) -> Result<Ty<I>, E> {
-        let interner = folder.interner();
-        Ok(match self.kind(interner) {
-            TyKind::BoundVar(bound_var) => {
-                if let Some(bound_var1) = bound_var.shifted_out_to(outer_binder) {
-                    // This variable was bound outside of the binders
-                    // that we have traversed during folding;
-                    // therefore, it is free. Let the folder have a
-                    // crack at it.
-                    folder.try_fold_free_var_ty(bound_var1, outer_binder)?
-                } else {
-                    // This variable was bound within the binders that
-                    // we folded over, so just return a bound
-                    // variable.
-                    self
-                }
-            }
-            TyKind::Dyn(clauses) => {
-                TyKind::Dyn(clauses.clone().try_fold_with(folder, outer_binder)?)
-                    .intern(folder.interner())
-            }
-            TyKind::InferenceVar(var, kind) => {
-                folder.try_fold_inference_ty(*var, *kind, outer_binder)?
-            }
-            TyKind::Placeholder(ui) => folder.try_fold_free_placeholder_ty(*ui, outer_binder)?,
-            TyKind::Alias(proj) => TyKind::Alias(proj.clone().try_fold_with(folder, outer_binder)?)
-                .intern(folder.interner()),
-            TyKind::Function(fun) => {
-                TyKind::Function(fun.clone().try_fold_with(folder, outer_binder)?)
-                    .intern(folder.interner())
-            }
-            TyKind::Adt(id, substitution) => TyKind::Adt(
-                id.try_fold_with(folder, outer_binder)?,
-                substitution.clone().try_fold_with(folder, outer_binder)?,
-            )
-            .intern(folder.interner()),
-            TyKind::AssociatedType(assoc_ty, substitution) => TyKind::AssociatedType(
-                assoc_ty.try_fold_with(folder, outer_binder)?,
-                substitution.clone().try_fold_with(folder, outer_binder)?,
-            )
-            .intern(folder.interner()),
-            TyKind::Scalar(scalar) => TyKind::Scalar(scalar.try_fold_with(folder, outer_binder)?)
-                .intern(folder.interner()),
-            TyKind::Str => TyKind::Str.intern(folder.interner()),
-            TyKind::Tuple(arity, substitution) => TyKind::Tuple(
-                *arity,
-                substitution.clone().try_fold_with(folder, outer_binder)?,
-            )
-            .intern(folder.interner()),
-            TyKind::OpaqueType(opaque_ty, substitution) => TyKind::OpaqueType(
-                opaque_ty.try_fold_with(folder, outer_binder)?,
-                substitution.clone().try_fold_with(folder, outer_binder)?,
-            )
-            .intern(folder.interner()),
-            TyKind::Slice(substitution) => {
-                TyKind::Slice(substitution.clone().try_fold_with(folder, outer_binder)?)
-                    .intern(folder.interner())
-            }
-            TyKind::FnDef(fn_def, substitution) => TyKind::FnDef(
-                fn_def.try_fold_with(folder, outer_binder)?,
-                substitution.clone().try_fold_with(folder, outer_binder)?,
-            )
-            .intern(folder.interner()),
-            TyKind::Ref(mutability, lifetime, ty) => TyKind::Ref(
-                mutability.try_fold_with(folder, outer_binder)?,
-                lifetime.clone().try_fold_with(folder, outer_binder)?,
-                ty.clone().try_fold_with(folder, outer_binder)?,
-            )
-            .intern(folder.interner()),
-            TyKind::Raw(mutability, ty) => TyKind::Raw(
-                mutability.try_fold_with(folder, outer_binder)?,
-                ty.clone().try_fold_with(folder, outer_binder)?,
-            )
-            .intern(folder.interner()),
-            TyKind::Never => TyKind::Never.intern(folder.interner()),
-            TyKind::Array(ty, const_) => TyKind::Array(
-                ty.clone().try_fold_with(folder, outer_binder)?,
-                const_.clone().try_fold_with(folder, outer_binder)?,
-            )
-            .intern(folder.interner()),
-            TyKind::Closure(id, substitution) => TyKind::Closure(
-                id.try_fold_with(folder, outer_binder)?,
-                substitution.clone().try_fold_with(folder, outer_binder)?,
-            )
-            .intern(folder.interner()),
-            TyKind::Generator(id, substitution) => TyKind::Generator(
-                id.try_fold_with(folder, outer_binder)?,
-                substitution.clone().try_fold_with(folder, outer_binder)?,
-            )
-            .intern(folder.interner()),
-            TyKind::GeneratorWitness(id, substitution) => TyKind::GeneratorWitness(
-                id.try_fold_with(folder, outer_binder)?,
-                substitution.clone().try_fold_with(folder, outer_binder)?,
-            )
-            .intern(folder.interner()),
-            TyKind::Foreign(id) => {
-                TyKind::Foreign(id.try_fold_with(folder, outer_binder)?).intern(folder.interner())
-            }
-            TyKind::Error => TyKind::Error.intern(folder.interner()),
-        })
-    }
-}
-
-/// "Folding" a lifetime invokes the `fold_lifetime` method on the folder; this
-/// usually (in turn) invokes `super_fold_lifetime` to fold the individual
-/// parts.
-impl<I: Interner> TypeFoldable<I> for Lifetime<I> {
-    fn try_fold_with<E>(
-        self,
-        folder: &mut dyn FallibleTypeFolder<I, Error = E>,
-        outer_binder: DebruijnIndex,
-    ) -> Result<Self, E> {
-        folder.try_fold_lifetime(self, outer_binder)
-    }
-}
-
-impl<I> TypeSuperFoldable<I> for Lifetime<I>
-where
-    I: Interner,
-{
-    fn try_super_fold_with<E>(
-        self,
-        folder: &mut dyn FallibleTypeFolder<I, Error = E>,
-        outer_binder: DebruijnIndex,
-    ) -> Result<Lifetime<I>, E> {
-        let interner = folder.interner();
-        match self.data(interner) {
-            LifetimeData::BoundVar(bound_var) => {
-                if let Some(bound_var1) = bound_var.shifted_out_to(outer_binder) {
-                    // This variable was bound outside of the binders
-                    // that we have traversed during folding;
-                    // therefore, it is free. Let the folder have a
-                    // crack at it.
-                    folder.try_fold_free_var_lifetime(bound_var1, outer_binder)
-                } else {
-                    // This variable was bound within the binders that
-                    // we folded over, so just return a bound
-                    // variable.
-                    Ok(self)
-                }
-            }
-            LifetimeData::InferenceVar(var) => {
-                folder.try_fold_inference_lifetime(*var, outer_binder)
-            }
-            LifetimeData::Placeholder(universe) => {
-                folder.try_fold_free_placeholder_lifetime(*universe, outer_binder)
-            }
-            LifetimeData::Static => Ok(LifetimeData::<I>::Static.intern(folder.interner())),
-            LifetimeData::Erased => Ok(LifetimeData::<I>::Erased.intern(folder.interner())),
-            LifetimeData::Phantom(void, ..) => match *void {},
-        }
-    }
-}
-
-/// "Folding" a const invokes the `fold_const` method on the folder; this
-/// usually (in turn) invokes `super_fold_const` to fold the individual
-/// parts.
-impl<I: Interner> TypeFoldable<I> for Const<I> {
-    fn try_fold_with<E>(
-        self,
-        folder: &mut dyn FallibleTypeFolder<I, Error = E>,
-        outer_binder: DebruijnIndex,
-    ) -> Result<Self, E> {
-        folder.try_fold_const(self, outer_binder)
-    }
-}
-
-impl<I> TypeSuperFoldable<I> for Const<I>
-where
-    I: Interner,
-{
-    fn try_super_fold_with<E>(
-        self,
-        folder: &mut dyn FallibleTypeFolder<I, Error = E>,
-        outer_binder: DebruijnIndex,
-    ) -> Result<Const<I>, E> {
-        let interner = folder.interner();
-        let ConstData { ref ty, ref value } = self.data(interner);
-        let mut fold_ty = || ty.clone().try_fold_with(folder, outer_binder);
-        match value {
-            ConstValue::BoundVar(bound_var) => {
-                if let Some(bound_var1) = bound_var.shifted_out_to(outer_binder) {
-                    folder.try_fold_free_var_const(ty.clone(), bound_var1, outer_binder)
-                } else {
-                    Ok(self)
-                }
-            }
-            ConstValue::InferenceVar(var) => {
-                folder.try_fold_inference_const(ty.clone(), *var, outer_binder)
-            }
-            ConstValue::Placeholder(universe) => {
-                folder.try_fold_free_placeholder_const(ty.clone(), *universe, outer_binder)
-            }
-            ConstValue::Concrete(ev) => Ok(ConstData {
-                ty: fold_ty()?,
-                value: ConstValue::Concrete(ConcreteConst {
-                    interned: ev.interned.clone(),
-                }),
-            }
-            .intern(folder.interner())),
-        }
-    }
-}
-
-/// Folding a goal invokes the `fold_goal` callback (which will, by
-/// default, invoke super-fold).
-impl<I: Interner> TypeFoldable<I> for Goal<I> {
-    fn try_fold_with<E>(
-        self,
-        folder: &mut dyn FallibleTypeFolder<I, Error = E>,
-        outer_binder: DebruijnIndex,
-    ) -> Result<Self, E> {
-        folder.try_fold_goal(self, outer_binder)
-    }
-}
-
-/// Superfold folds recursively.
-impl<I: Interner> TypeSuperFoldable<I> for Goal<I> {
-    fn try_super_fold_with<E>(
-        self,
-        folder: &mut dyn FallibleTypeFolder<I, Error = E>,
-        outer_binder: DebruijnIndex,
-    ) -> Result<Self, E> {
-        let interner = folder.interner();
-        Ok(Goal::new(
-            interner,
-            self.data(interner)
-                .clone()
-                .try_fold_with(folder, outer_binder)?,
-        ))
-    }
-}
-
-/// Folding a program clause invokes the `fold_program_clause`
-/// callback on the folder (which will, by default, invoke the
-/// `super_fold_with` method on the program clause).
-impl<I: Interner> TypeFoldable<I> for ProgramClause<I> {
-    fn try_fold_with<E>(
-        self,
-        folder: &mut dyn FallibleTypeFolder<I, Error = E>,
-        outer_binder: DebruijnIndex,
-    ) -> Result<Self, E> {
-        folder.try_fold_program_clause(self, outer_binder)
-    }
-}
diff --git a/vendor/chalk-ir/src/fold/binder_impls.rs b/vendor/chalk-ir/src/fold/binder_impls.rs
deleted file mode 100644
index 1f44c1629..000000000
--- a/vendor/chalk-ir/src/fold/binder_impls.rs
+++ /dev/null
@@ -1,73 +0,0 @@
-//! This module contains impls of `TypeFoldable` for those types that
-//! introduce binders.
-//!
-//! The more interesting impls of `TypeFoldable` remain in the `fold` module.
-
-use crate::*;
-
-impl<I: Interner> TypeFoldable<I> for FnPointer<I> {
-    fn try_fold_with<E>(
-        self,
-        folder: &mut dyn FallibleTypeFolder<I, Error = E>,
-        outer_binder: DebruijnIndex,
-    ) -> Result<Self, E> {
-        let FnPointer {
-            num_binders,
-            substitution,
-            sig,
-        } = self;
-        Ok(FnPointer {
-            num_binders,
-            substitution: substitution.try_fold_with(folder, outer_binder.shifted_in())?,
-            sig: FnSig {
-                abi: sig.abi,
-                safety: sig.safety,
-                variadic: sig.variadic,
-            },
-        })
-    }
-}
-
-impl<T, I: Interner> TypeFoldable<I> for Binders<T>
-where
-    T: HasInterner<Interner = I> + TypeFoldable<I>,
-    I: Interner,
-{
-    fn try_fold_with<E>(
-        self,
-        folder: &mut dyn FallibleTypeFolder<I, Error = E>,
-        outer_binder: DebruijnIndex,
-    ) -> Result<Self, E> {
-        let Binders {
-            binders: self_binders,
-            value: self_value,
-        } = self;
-        let value = self_value.try_fold_with(folder, outer_binder.shifted_in())?;
-        let binders = VariableKinds {
-            interned: self_binders.interned().clone(),
-        };
-        Ok(Binders::new(binders, value))
-    }
-}
-
-impl<I, T> TypeFoldable<I> for Canonical<T>
-where
-    I: Interner,
-    T: HasInterner<Interner = I> + TypeFoldable<I>,
-{
-    fn try_fold_with<E>(
-        self,
-        folder: &mut dyn FallibleTypeFolder<I, Error = E>,
-        outer_binder: DebruijnIndex,
-    ) -> Result<Self, E> {
-        let Canonical {
-            binders: self_binders,
-            value: self_value,
-        } = self;
-        let value = self_value.try_fold_with(folder, outer_binder.shifted_in())?;
-        let binders = CanonicalVarKinds {
-            interned: self_binders.interned().clone(),
-        };
-        Ok(Canonical { binders, value })
-    }
-}
diff --git a/vendor/chalk-ir/src/fold/boring_impls.rs b/vendor/chalk-ir/src/fold/boring_impls.rs
deleted file mode 100644
index fb4e3e30b..000000000
--- a/vendor/chalk-ir/src/fold/boring_impls.rs
+++ /dev/null
@@ -1,244 +0,0 @@
-//! This module contains "rote and uninteresting" impls of `TypeFoldable` for
-//! various types. In general, we prefer to derive `TypeFoldable`, but
-//! sometimes that doesn't work for whatever reason.
-//!
-//! The more interesting impls of `TypeFoldable` remain in the `fold` module.
-
-use super::in_place;
-use crate::*;
-use std::marker::PhantomData;
-
-impl<T: TypeFoldable<I>, I: Interner> TypeFoldable<I> for Vec<T> {
-    fn try_fold_with<E>(
-        self,
-        folder: &mut dyn FallibleTypeFolder<I, Error = E>,
-        outer_binder: DebruijnIndex,
-    ) -> Result<Self, E> {
-        in_place::fallible_map_vec(self, |e| e.try_fold_with(folder, outer_binder))
-    }
-}
-
-impl<T: TypeFoldable<I>, I: Interner> TypeFoldable<I> for Box<T> {
-    fn try_fold_with<E>(
-        self,
-        folder: &mut dyn FallibleTypeFolder<I, Error = E>,
-        outer_binder: DebruijnIndex,
-    ) -> Result<Self, E> {
-        in_place::fallible_map_box(self, |e| e.try_fold_with(folder, outer_binder))
-    }
-}
-
-macro_rules! tuple_fold {
-    ($($n:ident),*) => {
-        impl<$($n: TypeFoldable<I>,)* I: Interner> TypeFoldable<I> for ($($n,)*) {
-            fn try_fold_with<Error>(self, folder: &mut dyn FallibleTypeFolder<I, Error = Error>, outer_binder: DebruijnIndex) -> Result<Self, Error>
-            {
-                #[allow(non_snake_case)]
-                let ($($n),*) = self;
-                Ok(($($n.try_fold_with(folder, outer_binder)?,)*))
-            }
-        }
-    }
-}
-
-tuple_fold!(A, B);
-tuple_fold!(A, B, C);
-tuple_fold!(A, B, C, D);
-tuple_fold!(A, B, C, D, E);
-
-impl<T: TypeFoldable<I>, I: Interner> TypeFoldable<I> for Option<T> {
-    fn try_fold_with<E>(
-        self,
-        folder: &mut dyn FallibleTypeFolder<I, Error = E>,
-        outer_binder: DebruijnIndex,
-    ) -> Result<Self, E> {
-        match self {
-            None => Ok(None),
-            Some(e) => Ok(Some(e.try_fold_with(folder, outer_binder)?)),
-        }
-    }
-}
-
-impl<I: Interner> TypeFoldable<I> for GenericArg<I> {
-    fn try_fold_with<E>(
-        self,
-        folder: &mut dyn FallibleTypeFolder<I, Error = E>,
-        outer_binder: DebruijnIndex,
-    ) -> Result<Self, E> {
-        let interner = folder.interner();
-
-        let data = self
-            .data(interner)
-            .clone()
-            .try_fold_with(folder, outer_binder)?;
-        Ok(GenericArg::new(interner, data))
-    }
-}
-
-impl<I: Interner> TypeFoldable<I> for Substitution<I> {
-    fn try_fold_with<E>(
-        self,
-        folder: &mut dyn FallibleTypeFolder<I, Error = E>,
-        outer_binder: DebruijnIndex,
-    ) -> Result<Self, E> {
-        let interner = folder.interner();
-
-        let folded = self
-            .iter(interner)
-            .cloned()
-            .map(|p| p.try_fold_with(folder, outer_binder));
-        Substitution::from_fallible(interner, folded)
-    }
-}
-
-impl<I: Interner> TypeFoldable<I> for Goals<I> {
-    fn try_fold_with<E>(
-        self,
-        folder: &mut dyn FallibleTypeFolder<I, Error = E>,
-        outer_binder: DebruijnIndex,
-    ) -> Result<Self, E> {
-        let interner = folder.interner();
-        let folded = self
-            .iter(interner)
-            .cloned()
-            .map(|p| p.try_fold_with(folder, outer_binder));
-        Goals::from_fallible(interner, folded)
-    }
-}
-
-impl<I: Interner> TypeFoldable<I> for ProgramClauses<I> {
-    fn try_fold_with<E>(
-        self,
-        folder: &mut dyn FallibleTypeFolder<I, Error = E>,
-        outer_binder: DebruijnIndex,
-    ) -> Result<Self, E> {
-        let interner = folder.interner();
-        let folded = self
-            .iter(interner)
-            .cloned()
-            .map(|p| p.try_fold_with(folder, outer_binder));
-        ProgramClauses::from_fallible(interner, folded)
-    }
-}
-
-impl<I: Interner> TypeFoldable<I> for QuantifiedWhereClauses<I> {
-    fn try_fold_with<E>(
-        self,
-        folder: &mut dyn FallibleTypeFolder<I, Error = E>,
-        outer_binder: DebruijnIndex,
-    ) -> Result<Self, E> {
-        let interner = folder.interner();
-        let folded = self
-            .iter(interner)
-            .cloned()
-            .map(|p| p.try_fold_with(folder, outer_binder));
-        QuantifiedWhereClauses::from_fallible(interner, folded)
-    }
-}
-
-impl<I: Interner> TypeFoldable<I> for Constraints<I> {
-    fn try_fold_with<E>(
-        self,
-        folder: &mut dyn FallibleTypeFolder<I, Error = E>,
-        outer_binder: DebruijnIndex,
-    ) -> Result<Self, E> {
-        let interner = folder.interner();
-        let folded = self
-            .iter(interner)
-            .cloned()
-            .map(|p| p.try_fold_with(folder, outer_binder));
-        Constraints::from_fallible(interner, folded)
-    }
-}
-
-#[doc(hidden)]
-#[macro_export]
-macro_rules! copy_fold {
-    ($t:ty) => {
-        impl<I: Interner> $crate::fold::TypeFoldable<I> for $t {
-            fn try_fold_with<E>(
-                self,
-                _folder: &mut dyn ($crate::fold::FallibleTypeFolder<I, Error = E>),
-                _outer_binder: DebruijnIndex,
-            ) -> ::std::result::Result<Self, E> {
-                Ok(self)
-            }
-        }
-    };
-}
-
-copy_fold!(bool);
-copy_fold!(usize);
-copy_fold!(UniverseIndex);
-copy_fold!(PlaceholderIndex);
-copy_fold!(QuantifierKind);
-copy_fold!(DebruijnIndex);
-copy_fold!(());
-copy_fold!(UintTy);
-copy_fold!(IntTy);
-copy_fold!(FloatTy);
-copy_fold!(Scalar);
-copy_fold!(ClausePriority);
-copy_fold!(Mutability);
-copy_fold!(Safety);
-
-#[doc(hidden)]
-#[macro_export]
-macro_rules! id_fold {
-    ($t:ident) => {
-        impl<I: Interner> $crate::fold::TypeFoldable<I> for $t<I> {
-            fn try_fold_with<E>(
-                self,
-                _folder: &mut dyn ($crate::fold::FallibleTypeFolder<I, Error = E>),
-                _outer_binder: DebruijnIndex,
-            ) -> ::std::result::Result<Self, E> {
-                Ok(self)
-            }
-        }
-    };
-}
-
-id_fold!(ImplId);
-id_fold!(AdtId);
-id_fold!(TraitId);
-id_fold!(AssocTypeId);
-id_fold!(OpaqueTyId);
-id_fold!(FnDefId);
-id_fold!(ClosureId);
-id_fold!(GeneratorId);
-id_fold!(ForeignDefId);
-
-impl<I: Interner> TypeSuperFoldable<I> for ProgramClauseData<I> {
-    fn try_super_fold_with<E>(
-        self,
-        folder: &mut dyn FallibleTypeFolder<I, Error = E>,
-        outer_binder: DebruijnIndex,
-    ) -> ::std::result::Result<Self, E> {
-        Ok(ProgramClauseData(
-            self.0.try_fold_with(folder, outer_binder)?,
-        ))
-    }
-}
-
-impl<I: Interner> TypeSuperFoldable<I> for ProgramClause<I> {
-    fn try_super_fold_with<E>(
-        self,
-        folder: &mut dyn FallibleTypeFolder<I, Error = E>,
-        outer_binder: DebruijnIndex,
-    ) -> ::std::result::Result<Self, E> {
-        let clause = self.data(folder.interner()).clone();
-        Ok(clause
-            .try_super_fold_with(folder, outer_binder)?
-            .intern(folder.interner()))
-    }
-}
-
-impl<I: Interner> TypeFoldable<I> for PhantomData<I> {
-    fn try_fold_with<E>(
-        self,
-        _folder: &mut dyn FallibleTypeFolder<I, Error = E>,
-        _outer_binder: DebruijnIndex,
-    ) -> ::std::result::Result<Self, E> {
-        Ok(PhantomData)
-    }
-}
diff --git a/vendor/chalk-ir/src/fold/in_place.rs b/vendor/chalk-ir/src/fold/in_place.rs
deleted file mode 100644
index 263da617d..000000000
--- a/vendor/chalk-ir/src/fold/in_place.rs
+++ /dev/null
@@ -1,263 +0,0 @@
-//! Subroutines to help implementers of `TypeFoldable` avoid unnecessary heap allocations.
-
-use std::marker::PhantomData;
-use std::{mem, ptr};
-
-fn is_zst<T>() -> bool {
-    mem::size_of::<T>() == 0
-}
-
-fn is_layout_identical<T, U>() -> bool {
-    mem::size_of::<T>() == mem::size_of::<U>() && mem::align_of::<T>() == mem::align_of::<U>()
-}
-
-/// Maps a `Box<T>` to a `Box<U>`, reusing the underlying storage if possible.
-pub(super) fn fallible_map_box<T, U, E>(
-    b: Box<T>,
-    map: impl FnOnce(T) -> Result<U, E>,
-) -> Result<Box<U>, E> {
-    // This optimization is only valid when `T` and `U` have the same size/alignment and is not
-    // useful for ZSTs.
-    if !is_layout_identical::<T, U>() || is_zst::<T>() {
-        return map(*b).map(Box::new);
-    }
-
-    let raw = Box::into_raw(b);
-    unsafe {
-        let val = ptr::read(raw);
-
-        // Box<T> -> Box<MaybeUninit<U>>
-        let mut raw: Box<mem::MaybeUninit<U>> = Box::from_raw(raw.cast());
-
-        // If `map` panics or returns an error, `raw` will free the memory associated with `b`, but
-        // not drop the boxed value itself since it is wrapped in `MaybeUninit`. This is what we
-        // want since the boxed value was moved into `map`.
-        let mapped_val = map(val)?;
-        ptr::write(raw.as_mut_ptr(), mapped_val);
-
-        // Box<MaybeUninit<U>> -> Box<U>
-        Ok(Box::from_raw(Box::into_raw(raw).cast()))
-    }
-}
-
-/// Maps a `Vec<T>` to a `Vec<U>`, reusing the underlying storage if possible.
-pub(super) fn fallible_map_vec<T, U, E>(
-    vec: Vec<T>,
-    mut map: impl FnMut(T) -> Result<U, E>,
-) -> Result<Vec<U>, E> {
-    // This optimization is only valid when `T` and `U` have the same size/alignment and is not
-    // useful for ZSTs.
-    if !is_layout_identical::<T, U>() || is_zst::<T>() {
-        return vec.into_iter().map(map).collect();
-    }
-
-    let mut vec = VecMappedInPlace::<T, U>::new(vec);
-
-    unsafe {
-        for i in 0..vec.len {
-            let place = vec.ptr.add(i);
-            let val = ptr::read(place);
-
-            // Set `map_in_progress` so the drop impl for `VecMappedInPlace` can handle the other
-            // elements correctly in case `map` panics or returns an error.
-            vec.map_in_progress = i;
-            let mapped_val = map(val)?;
-
-            ptr::write(place as *mut U, mapped_val);
-        }
-
-        Ok(vec.finish())
-    }
-}
-
-/// Takes ownership of a `Vec` that is being mapped in place, cleaning up if the map fails.
-struct VecMappedInPlace<T, U> {
-    ptr: *mut T,
-    len: usize,
-    cap: usize,
-
-    map_in_progress: usize,
-    _elem_tys: PhantomData<(T, U)>,
-}
-
-impl<T, U> VecMappedInPlace<T, U> {
-    fn new(mut vec: Vec<T>) -> Self {
-        assert!(is_layout_identical::<T, U>());
-
-        // FIXME: This is just `Vec::into_raw_parts`. Use that instead when it is stabilized.
-        let ptr = vec.as_mut_ptr();
-        let len = vec.len();
-        let cap = vec.capacity();
-        mem::forget(vec);
-
-        VecMappedInPlace {
-            ptr,
-            len,
-            cap,
-
-            map_in_progress: 0,
-            _elem_tys: PhantomData,
-        }
-    }
-
-    /// Converts back into a `Vec` once the map is complete.
-    unsafe fn finish(self) -> Vec<U> {
-        let this = mem::ManuallyDrop::new(self);
-        Vec::from_raw_parts(this.ptr as *mut U, this.len, this.cap)
-    }
-}
-
-/// `VecMappedInPlace` drops everything but the element that was passed to `map` when it panicked or
-/// returned an error. Everything before that index in the vector has type `U` (it has been mapped)
-/// and everything after it has type `T` (it has not been mapped).
-///
-/// ```text
-///  mapped
-///  |      not yet mapped
-///  |----| |-----|
-/// [UUUU UxTT TTTT]
-///        ^
-///    `map_in_progress` (not dropped)
-/// ```
-impl<T, U> Drop for VecMappedInPlace<T, U> {
-    fn drop(&mut self) {
-        // Drop mapped elements of type `U`.
-        for i in 0..self.map_in_progress {
-            unsafe {
-                ptr::drop_in_place(self.ptr.add(i) as *mut U);
-            }
-        }
-
-        // Drop unmapped elements of type `T`.
-        for i in (self.map_in_progress + 1)..self.len {
-            unsafe {
-                ptr::drop_in_place(self.ptr.add(i));
-            }
-        }
-
-        // Free the underlying storage for the `Vec`.
-        // `len` is 0 because the elements were handled above.
-        unsafe {
-            Vec::from_raw_parts(self.ptr, 0, self.cap);
-        }
-    }
-}
-
-#[cfg(test)]
-mod tests {
-    use std::fmt;
-    use std::sync::{Arc, Mutex};
-
-    /// A wrapper around `T` that records when it is dropped.
-    struct RecordDrop<T: fmt::Display> {
-        id: T,
-        drops: Arc<Mutex<Vec<String>>>,
-    }
-
-    impl<T: fmt::Display> RecordDrop<T> {
-        fn new(id: T, drops: &Arc<Mutex<Vec<String>>>) -> Self {
-            RecordDrop {
-                id,
-                drops: drops.clone(),
-            }
-        }
-    }
-
-    impl RecordDrop<u8> {
-        fn map_to_char(self) -> RecordDrop<char> {
-            let this = std::mem::ManuallyDrop::new(self);
-            RecordDrop {
-                id: (this.id + b'A') as char,
-                drops: this.drops.clone(),
-            }
-        }
-    }
-
-    impl<T: fmt::Display> Drop for RecordDrop<T> {
-        fn drop(&mut self) {
-            self.drops.lock().unwrap().push(format!("{}", self.id));
-        }
-    }
-
-    #[test]
-    fn vec_no_cleanup_after_success() {
-        let drops = Arc::new(Mutex::new(Vec::new()));
-        let to_fold = (0u8..5).map(|i| RecordDrop::new(i, &drops)).collect();
-
-        let res: Result<_, ()> = super::fallible_map_vec(to_fold, |x| Ok(x.map_to_char()));
-
-        assert!(res.is_ok());
-        assert!(drops.lock().unwrap().is_empty());
-    }
-
-    #[test]
-    fn vec_cleanup_after_panic() {
-        let drops = Arc::new(Mutex::new(Vec::new()));
-        let to_fold = (0u8..5).map(|i| RecordDrop::new(i, &drops)).collect();
-
-        let res = std::panic::catch_unwind(|| {
-            let _: Result<_, ()> = super::fallible_map_vec(to_fold, |x| {
-                if x.id == 3 {
-                    panic!();
-                }
-
-                Ok(x.map_to_char())
-            });
-        });
-
-        assert!(res.is_err());
-        assert_eq!(*drops.lock().unwrap(), &["3", "A", "B", "C", "4"]);
-    }
-
-    #[test]
-    fn vec_cleanup_after_early_return() {
-        let drops = Arc::new(Mutex::new(Vec::new()));
-        let to_fold = (0u8..5).map(|i| RecordDrop::new(i, &drops)).collect();
-
-        let res = super::fallible_map_vec(to_fold, |x| {
-            if x.id == 2 {
-                return Err(());
-            }
-
-            Ok(x.map_to_char())
-        });
-
-        assert!(res.is_err());
-        assert_eq!(*drops.lock().unwrap(), &["2", "A", "B", "3", "4"]);
-    }
-
-    #[test]
-    fn box_no_cleanup_after_success() {
-        let drops = Arc::new(Mutex::new(Vec::new()));
-        let to_fold = Box::new(RecordDrop::new(0, &drops));
-
-        let res: Result<Box<_>, ()> = super::fallible_map_box(to_fold, |x| Ok(x.map_to_char()));
-
-        assert!(res.is_ok());
-        assert!(drops.lock().unwrap().is_empty());
-    }
-
-    #[test]
-    fn box_cleanup_after_panic() {
-        let drops = Arc::new(Mutex::new(Vec::new()));
-        let to_fold = Box::new(RecordDrop::new(0, &drops));
-
-        let res = std::panic::catch_unwind(|| {
-            let _: Result<Box<()>, ()> = super::fallible_map_box(to_fold, |_| panic!());
-        });
-
-        assert!(res.is_err());
-        assert_eq!(*drops.lock().unwrap(), &["0"]);
-    }
-
-    #[test]
-    fn box_cleanup_after_early_return() {
-        let drops = Arc::new(Mutex::new(Vec::new()));
-        let to_fold = Box::new(RecordDrop::new(0, &drops));
-
-        let res: Result<Box<()>, _> = super::fallible_map_box(to_fold, |_| Err(()));
-
-        assert!(res.is_err());
-        assert_eq!(*drops.lock().unwrap(), &["0"]);
-    }
-}
diff --git a/vendor/chalk-ir/src/fold/shift.rs b/vendor/chalk-ir/src/fold/shift.rs
deleted file mode 100644
index f7e5e4a4a..000000000
--- a/vendor/chalk-ir/src/fold/shift.rs
+++ /dev/null
@@ -1,177 +0,0 @@
-//! Shifting of debruijn indices
-
-use crate::*;
-
-/// Methods for converting debruijn indices to move values into or out
-/// of binders.
-pub trait Shift<I: Interner>: TypeFoldable<I> {
-    /// Shifts this term in one level of binders.
-    fn shifted_in(self, interner: I) -> Self;
-
-    /// Shifts a term valid at `outer_binder` so that it is
-    /// valid at the innermost binder. See [`DebruijnIndex::shifted_in_from`]
-    /// for a detailed explanation.
-    fn shifted_in_from(self, interner: I, source_binder: DebruijnIndex) -> Self;
-
-    /// Shifts this term out one level of binders.
-    fn shifted_out(self, interner: I) -> Fallible<Self>;
-
-    /// Shifts a term valid at the innermost binder so that it is
-    /// valid at `outer_binder`. See [`DebruijnIndex::shifted_out_to`]
-    /// for a detailed explanation.
-    fn shifted_out_to(self, interner: I, target_binder: DebruijnIndex) -> Fallible<Self>;
-}
-
-impl<T: TypeFoldable<I>, I: Interner> Shift<I> for T {
-    fn shifted_in(self, interner: I) -> Self {
-        self.shifted_in_from(interner, DebruijnIndex::ONE)
-    }
-
-    fn shifted_in_from(self, interner: I, source_binder: DebruijnIndex) -> T {
-        self.try_fold_with(
-            &mut Shifter {
-                source_binder,
-                interner,
-            },
-            DebruijnIndex::INNERMOST,
-        )
-        .unwrap()
-    }
-
-    fn shifted_out_to(self, interner: I, target_binder: DebruijnIndex) -> Fallible<T> {
-        self.try_fold_with(
-            &mut DownShifter {
-                target_binder,
-                interner,
-            },
-            DebruijnIndex::INNERMOST,
-        )
-    }
-
-    fn shifted_out(self, interner: I) -> Fallible<Self> {
-        self.shifted_out_to(interner, DebruijnIndex::ONE)
-    }
-}
-
-/// A folder that adjusts debruijn indices by a certain amount.
-#[derive(FallibleTypeFolder)]
-struct Shifter<I: Interner> {
-    source_binder: DebruijnIndex,
-    interner: I,
-}
-
-impl<I: Interner> Shifter<I> {
-    /// Given a free variable at `depth`, shifts that depth to `depth
-    /// + self.adjustment`, and then wraps *that* within the internal
-    /// set `binders`.
-    fn adjust(&self, bound_var: BoundVar, outer_binder: DebruijnIndex) -> BoundVar {
-        bound_var
-            .shifted_in_from(self.source_binder)
-            .shifted_in_from(outer_binder)
-    }
-}
-
-impl<I: Interner> TypeFolder<I> for Shifter<I> {
-    fn as_dyn(&mut self) -> &mut dyn TypeFolder<I> {
-        self
-    }
-
-    fn fold_free_var_ty(&mut self, bound_var: BoundVar, outer_binder: DebruijnIndex) -> Ty<I> {
-        TyKind::<I>::BoundVar(self.adjust(bound_var, outer_binder))
-            .intern(TypeFolder::interner(self))
-    }
-
-    fn fold_free_var_lifetime(
-        &mut self,
-        bound_var: BoundVar,
-        outer_binder: DebruijnIndex,
-    ) -> Lifetime<I> {
-        LifetimeData::<I>::BoundVar(self.adjust(bound_var, outer_binder))
-            .intern(TypeFolder::interner(self))
-    }
-
-    fn fold_free_var_const(
-        &mut self,
-        ty: Ty<I>,
-        bound_var: BoundVar,
-        outer_binder: DebruijnIndex,
-    ) -> Const<I> {
-        // const types don't have free variables, so we can skip folding `ty`
-        self.adjust(bound_var, outer_binder)
-            .to_const(TypeFolder::interner(self), ty)
-    }
-
-    fn interner(&self) -> I {
-        self.interner
-    }
-}
-
-//---------------------------------------------------------------------------
-
-/// A shifter that reduces debruijn indices -- in other words, which lifts a value
-/// *out* from binders. Consider this example:
-///
-struct DownShifter<I> {
-    target_binder: DebruijnIndex,
-    interner: I,
-}
-
-impl<I> DownShifter<I> {
-    /// Given a reference to a free variable at depth `depth`
-    /// (appearing within `binders` internal binders), attempts to
-    /// lift that free variable out from `adjustment` levels of
-    /// binders (i.e., convert it to depth `depth -
-    /// self.adjustment`). If the free variable is bound by one of
-    /// those internal binders (i.e., `depth < self.adjustment`) the
-    /// this will fail with `Err`. Otherwise, returns the variable at
-    /// this new depth (but adjusted to appear within `binders`).
-    fn adjust(&self, bound_var: BoundVar, outer_binder: DebruijnIndex) -> Fallible<BoundVar> {
-        match bound_var.shifted_out_to(self.target_binder) {
-            Some(bound_var1) => Ok(bound_var1.shifted_in_from(outer_binder)),
-            None => Err(NoSolution),
-        }
-    }
-}
-
-impl<I: Interner> FallibleTypeFolder<I> for DownShifter<I> {
-    type Error = NoSolution;
-
-    fn as_dyn(&mut self) -> &mut dyn FallibleTypeFolder<I, Error = Self::Error> {
-        self
-    }
-
-    fn try_fold_free_var_ty(
-        &mut self,
-        bound_var: BoundVar,
-        outer_binder: DebruijnIndex,
-    ) -> Fallible<Ty<I>> {
-        Ok(TyKind::<I>::BoundVar(self.adjust(bound_var, outer_binder)?).intern(self.interner()))
-    }
-
-    fn try_fold_free_var_lifetime(
-        &mut self,
-        bound_var: BoundVar,
-        outer_binder: DebruijnIndex,
-    ) -> Fallible<Lifetime<I>> {
-        Ok(
-            LifetimeData::<I>::BoundVar(self.adjust(bound_var, outer_binder)?)
-                .intern(self.interner()),
-        )
-    }
-
-    fn try_fold_free_var_const(
-        &mut self,
-        ty: Ty<I>,
-        bound_var: BoundVar,
-        outer_binder: DebruijnIndex,
-    ) -> Fallible<Const<I>> {
-        // const types don't have free variables, so we can skip folding `ty`
-        Ok(self
-            .adjust(bound_var, outer_binder)?
-            .to_const(self.interner(), ty))
-    }
-
-    fn interner(&self) -> I {
-        self.interner
-    }
-}
diff --git a/vendor/chalk-ir/src/fold/subst.rs b/vendor/chalk-ir/src/fold/subst.rs
deleted file mode 100644
index 7cff8d89c..000000000
--- a/vendor/chalk-ir/src/fold/subst.rs
+++ /dev/null
@@ -1,118 +0,0 @@
-use super::*;
-use crate::fold::shift::Shift;
-
-/// Substitution used during folding
-#[derive(FallibleTypeFolder)]
-pub struct Subst<'s, I: Interner> {
-    /// Values to substitute. A reference to a free variable with
-    /// index `i` will be mapped to `parameters[i]` -- if `i >
-    /// parameters.len()`, then we will leave the variable untouched.
-    parameters: &'s [GenericArg<I>],
-    interner: I,
-}
-
-impl<I: Interner> Subst<'_, I> {
-    /// Applies the substitution by folding
-    pub fn apply<T: TypeFoldable<I>>(interner: I, parameters: &[GenericArg<I>], value: T) -> T {
-        value
-            .try_fold_with(
-                &mut Subst {
-                    parameters,
-                    interner,
-                },
-                DebruijnIndex::INNERMOST,
-            )
-            .unwrap()
-    }
-}
-
-impl<I: Interner> TypeFolder<I> for Subst<'_, I> {
-    fn as_dyn(&mut self) -> &mut dyn TypeFolder<I> {
-        self
-    }
-
-    /// We are eliminating one binder, but binders outside of that get preserved.
-    ///
-    /// So e.g. consider this:
-    ///
-    /// ```notrust
-    /// for<A, B> { for<C> { [A, C] } }
-    /// //          ^ the binder we are substituing with `[u32]`
-    /// ```
-    ///
-    /// Here, `A` would be `^1.0` and `C` would be `^0.0`. We will replace `^0.0` with the
-    /// 0th index from the list (`u32`). We will convert `^1.0` (A) to `^0.0` -- i.e., shift
-    /// it **out** of one level of binder (the `for<C>` binder we are eliminating).
-    ///
-    /// This gives us as a result:
-    ///
-    /// ```notrust
-    /// for<A, B> { [A, u32] }
-    ///              ^ represented as `^0.0`
-    /// ```
-    fn fold_free_var_ty(&mut self, bound_var: BoundVar, outer_binder: DebruijnIndex) -> Ty<I> {
-        if let Some(index) = bound_var.index_if_innermost() {
-            match self.parameters[index].data(TypeFolder::interner(self)) {
-                GenericArgData::Ty(t) => t
-                    .clone()
-                    .shifted_in_from(TypeFolder::interner(self), outer_binder),
-                _ => panic!("mismatched kinds in substitution"),
-            }
-        } else {
-            bound_var
-                .shifted_out()
-                .expect("cannot fail because this is not the innermost")
-                .shifted_in_from(outer_binder)
-                .to_ty(TypeFolder::interner(self))
-        }
-    }
-
-    /// see `fold_free_var_ty`
-    fn fold_free_var_lifetime(
-        &mut self,
-        bound_var: BoundVar,
-        outer_binder: DebruijnIndex,
-    ) -> Lifetime<I> {
-        if let Some(index) = bound_var.index_if_innermost() {
-            match self.parameters[index].data(TypeFolder::interner(self)) {
-                GenericArgData::Lifetime(l) => l
-                    .clone()
-                    .shifted_in_from(TypeFolder::interner(self), outer_binder),
-                _ => panic!("mismatched kinds in substitution"),
-            }
-        } else {
-            bound_var
-                .shifted_out()
-                .unwrap()
-                .shifted_in_from(outer_binder)
-                .to_lifetime(TypeFolder::interner(self))
-        }
-    }
-
-    /// see `fold_free_var_ty`
-    fn fold_free_var_const(
-        &mut self,
-        ty: Ty<I>,
-        bound_var: BoundVar,
-        outer_binder: DebruijnIndex,
-    ) -> Const<I> {
-        if let Some(index) = bound_var.index_if_innermost() {
-            match self.parameters[index].data(TypeFolder::interner(self)) {
-                GenericArgData::Const(c) => c
-                    .clone()
-                    .shifted_in_from(TypeFolder::interner(self), outer_binder),
-                _ => panic!("mismatched kinds in substitution"),
-            }
-        } else {
-            bound_var
-                .shifted_out()
-                .unwrap()
-                .shifted_in_from(outer_binder)
-                .to_const(TypeFolder::interner(self), ty)
-        }
-    }
-
-    fn interner(&self) -> I {
-        self.interner
-    }
-}
diff --git a/vendor/chalk-ir/src/interner.rs b/vendor/chalk-ir/src/interner.rs
deleted file mode 100644
index 4959e4b74..000000000
--- a/vendor/chalk-ir/src/interner.rs
+++ /dev/null
@@ -1,702 +0,0 @@
-//! Encapsulates the concrete representation of core types such as types and goals.
-use crate::AliasTy;
-use crate::AssocTypeId;
-use crate::CanonicalVarKind;
-use crate::CanonicalVarKinds;
-use crate::ClosureId;
-use crate::Constraint;
-use crate::Constraints;
-use crate::FnDefId;
-use crate::ForeignDefId;
-use crate::GeneratorId;
-use crate::GenericArg;
-use crate::GenericArgData;
-use crate::Goal;
-use crate::GoalData;
-use crate::Goals;
-use crate::InEnvironment;
-use crate::Lifetime;
-use crate::LifetimeData;
-use crate::OpaqueTy;
-use crate::OpaqueTyId;
-use crate::ProgramClause;
-use crate::ProgramClauseData;
-use crate::ProgramClauseImplication;
-use crate::ProgramClauses;
-use crate::ProjectionTy;
-use crate::QuantifiedWhereClause;
-use crate::QuantifiedWhereClauses;
-use crate::SeparatorTraitRef;
-use crate::Substitution;
-use crate::TraitId;
-use crate::Ty;
-use crate::TyData;
-use crate::VariableKind;
-use crate::VariableKinds;
-use crate::Variance;
-use crate::Variances;
-use crate::{AdtId, TyKind};
-use crate::{Const, ConstData};
-use std::fmt::{self, Debug};
-use std::hash::Hash;
-use std::marker::PhantomData;
-use std::sync::Arc;
-
-/// A "interner" encapsulates the concrete representation of
-/// certain "core types" from chalk-ir. All the types in chalk-ir are
-/// parameterized by a `I: Interner`, and so (e.g.) if they want to
-/// store a type, they don't store a `Ty<I>` instance directly, but
-/// rather prefer a `Ty<I>`. You can think of `I::Type` as the
-/// interned representation (and, indeed, it may well be an interned
-/// pointer, e.g. in rustc).
-///
-/// Type families allow chalk to be embedded in different contexts
-/// where the concrete representation of core types varies. They also
-/// allow us to write generic code that reasons about multiple
-/// distinct sets of types by using distinct generic type parameters
-/// (e.g., `SourceI` and `TargetI`) -- even if those type parameters
-/// wind up being mapped to the same underlying type families in the
-/// end.
-pub trait Interner: Debug + Copy + Eq + Hash + Sized {
-    /// "Interned" representation of types.  In normal user code,
-    /// `Self::InternedType` is not referenced. Instead, we refer to
-    /// `Ty<Self>`, which wraps this type.
-    ///
-    /// An `InternedType` must be something that can be created from a
-    /// `TyKind` (by the [`intern_ty`][Self::intern_ty] method) and then later
-    /// converted back (by the [`ty_data`][Self::ty_data] method). The interned form
-    /// must also introduce indirection, either via a `Box`, `&`, or
-    /// other pointer type.
-    type InternedType: Debug + Clone + Eq + Hash;
-
-    /// "Interned" representation of lifetimes.  In normal user code,
-    /// `Self::InternedLifetime` is not referenced. Instead, we refer to
-    /// `Lifetime<Self>`, which wraps this type.
-    ///
-    /// An `InternedLifetime` must be something that can be created
-    /// from a `LifetimeData` (by the [`intern_lifetime`][Self::intern_lifetime] method) and
-    /// then later converted back (by the [`lifetime_data`][Self::lifetime_data] method).
-    type InternedLifetime: Debug + Clone + Eq + Hash;
-
-    /// "Interned" representation of const expressions. In normal user code,
-    /// `Self::InternedConst` is not referenced. Instead, we refer to
-    /// `Const<Self>`, which wraps this type.
-    ///
-    /// An `InternedConst` must be something that can be created
-    /// from a `ConstData` (by the [`intern_const`][Self::intern_const] method) and
-    /// then later converted back (by the [`const_data`][Self::const_data] method).
-    type InternedConst: Debug + Clone + Eq + Hash;
-
-    /// "Interned" representation of an evaluated const value.
-    /// `Self::InternedConcreteConst` is not referenced. Instead,
-    /// we refer to `ConcreteConst<Self>`, which wraps this type.
-    ///
-    /// `InternedConcreteConst` instances are not created by chalk,
-    /// it can only make a query asking about equality of two
-    /// evaluated consts.
-    type InternedConcreteConst: Debug + Clone + Eq + Hash;
-
-    /// "Interned" representation of a "generic parameter", which can
-    /// be either a type or a lifetime.  In normal user code,
-    /// `Self::InternedGenericArg` is not referenced. Instead, we refer to
-    /// `GenericArg<Self>`, which wraps this type.
-    ///
-    /// An `InternedType` is created by `intern_generic_arg` and can be
-    /// converted back to its underlying data via `generic_arg_data`.
-    type InternedGenericArg: Debug + Clone + Eq + Hash;
-
-    /// "Interned" representation of a "goal".  In normal user code,
-    /// `Self::InternedGoal` is not referenced. Instead, we refer to
-    /// `Goal<Self>`, which wraps this type.
-    ///
-    /// An `InternedGoal` is created by `intern_goal` and can be
-    /// converted back to its underlying data via `goal_data`.
-    type InternedGoal: Debug + Clone + Eq + Hash;
-
-    /// "Interned" representation of a list of goals.  In normal user code,
-    /// `Self::InternedGoals` is not referenced. Instead, we refer to
-    /// `Goals<Self>`, which wraps this type.
-    ///
-    /// An `InternedGoals` is created by `intern_goals` and can be
-    /// converted back to its underlying data via `goals_data`.
-    type InternedGoals: Debug + Clone + Eq + Hash;
-
-    /// "Interned" representation of a "substitution".  In normal user code,
-    /// `Self::InternedSubstitution` is not referenced. Instead, we refer to
-    /// `Substitution<Self>`, which wraps this type.
-    ///
-    /// An `InternedSubstitution` is created by `intern_substitution` and can be
-    /// converted back to its underlying data via `substitution_data`.
-    type InternedSubstitution: Debug + Clone + Eq + Hash;
-
-    /// "Interned" representation of a list of program clauses.  In normal user code,
-    /// `Self::InternedProgramClauses` is not referenced. Instead, we refer to
-    /// `ProgramClauses<Self>`, which wraps this type.
-    ///
-    /// An `InternedProgramClauses` is created by `intern_program_clauses` and can be
-    /// converted back to its underlying data via `program_clauses_data`.
-    type InternedProgramClauses: Debug + Clone + Eq + Hash;
-
-    /// "Interned" representation of a "program clause".  In normal user code,
-    /// `Self::InternedProgramClause` is not referenced. Instead, we refer to
-    /// `ProgramClause<Self>`, which wraps this type.
-    ///
-    /// An `InternedProgramClause` is created by `intern_program_clause` and can be
-    /// converted back to its underlying data via `program_clause_data`.
-    type InternedProgramClause: Debug + Clone + Eq + Hash;
-
-    /// "Interned" representation of a list of quantified where clauses.
-    /// In normal user code, `Self::InternedQuantifiedWhereClauses` is not referenced.
-    /// Instead, we refer to `QuantifiedWhereClauses<Self>`, which wraps this type.
-    ///
-    /// An `InternedQuantifiedWhereClauses` is created by `intern_quantified_where_clauses`
-    /// and can be converted back to its underlying data via `quantified_where_clauses_data`.
-    type InternedQuantifiedWhereClauses: Debug + Clone + Eq + Hash;
-
-    /// "Interned" representation of a list of variable kinds.
-    /// In normal user code, `Self::InternedVariableKinds` is not referenced.
-    /// Instead, we refer to `VariableKinds<Self>`, which wraps this type.
-    ///
-    /// An `InternedVariableKinds` is created by `intern_generic_arg_kinds`
-    /// and can be converted back to its underlying data via `variable_kinds_data`.
-    type InternedVariableKinds: Debug + Clone + Eq + Hash;
-
-    /// "Interned" representation of a list of variable kinds with universe index.
-    /// In normal user code, `Self::InternedCanonicalVarKinds` is not referenced.
-    /// Instead, we refer to `CanonicalVarKinds<Self>`, which wraps this type.
-    ///
-    /// An `InternedCanonicalVarKinds` is created by
-    /// `intern_canonical_var_kinds` and can be converted back
-    /// to its underlying data via `canonical_var_kinds_data`.
-    type InternedCanonicalVarKinds: Debug + Clone + Eq + Hash;
-
-    /// "Interned" representation of a list of region constraints.
-    /// In normal user code, `Self::InternedConstraints` is not referenced.
-    /// Instead, we refer to `Constraints<Self>`, which wraps this type.
-    ///
-    /// An `InternedConstraints` is created by `intern_constraints`
-    /// and can be converted back to its underlying data via `constraints_data`.
-    type InternedConstraints: Debug + Clone + Eq + Hash;
-
-    /// "Interned" representation of a list of `chalk_ir::Variance`.
-    /// In normal user code, `Self::InternedVariances` is not referenced.
-    /// Instead, we refer to `Variances<Self>`, which wraps this type.
-    ///
-    /// An `InternedVariances` is created by
-    /// `intern_variances` and can be converted back
-    /// to its underlying data via `variances_data`.
-    type InternedVariances: Debug + Clone + Eq + Hash;
-
-    /// The core "id" type used for trait-ids and the like.
-    type DefId: Debug + Copy + Eq + Hash;
-
-    /// The ID type for ADTs
-    type InternedAdtId: Debug + Copy + Eq + Hash;
-
-    /// Representation of identifiers.
-    type Identifier: Debug + Clone + Eq + Hash;
-
-    /// Representation of function ABI (e.g. calling convention).
-    type FnAbi: Debug + Copy + Eq + Hash;
-
-    /// Prints the debug representation of a type-kind-id.
-    /// Returns `None` to fallback to the default debug output.
-    #[allow(unused_variables)]
-    fn debug_adt_id(adt_id: AdtId<Self>, fmt: &mut fmt::Formatter<'_>) -> Option<fmt::Result> {
-        None
-    }
-
-    /// Prints the debug representation of a type-kind-id.
-    /// Returns `None` to fallback to the default debug output (e.g.,
-    /// if no info about current program is available from TLS).
-    #[allow(unused_variables)]
-    fn debug_trait_id(
-        trait_id: TraitId<Self>,
-        fmt: &mut fmt::Formatter<'_>,
-    ) -> Option<fmt::Result> {
-        None
-    }
-
-    /// Prints the debug representation of a type-kind-id.
-    /// Returns `None` to fallback to the default debug output.
-    #[allow(unused_variables)]
-    fn debug_assoc_type_id(
-        type_id: AssocTypeId<Self>,
-        fmt: &mut fmt::Formatter<'_>,
-    ) -> Option<fmt::Result> {
-        None
-    }
-
-    /// Prints the debug representation of an opaque type.
-    /// Returns `None` to fallback to the default debug output.
-    #[allow(unused_variables)]
-    fn debug_opaque_ty_id(
-        opaque_ty_id: OpaqueTyId<Self>,
-        fmt: &mut fmt::Formatter<'_>,
-    ) -> Option<fmt::Result> {
-        None
-    }
-
-    /// Prints the debug representation of a function-def-id.
-    /// Returns `None` to fallback to the default debug output.
-    #[allow(unused_variables)]
-    fn debug_fn_def_id(
-        fn_def_id: FnDefId<Self>,
-        fmt: &mut fmt::Formatter<'_>,
-    ) -> Option<fmt::Result> {
-        None
-    }
-
-    /// Prints the debug representation of a closure id.
-    /// Returns `None` to fallback to the default debug output.
-    #[allow(unused_variables)]
-    fn debug_closure_id(
-        fn_def_id: ClosureId<Self>,
-        fmt: &mut fmt::Formatter<'_>,
-    ) -> Option<fmt::Result> {
-        None
-    }
-
-    /// Prints the debug representation of a foreign-def-id.
-    /// Returns `None` to fallback to the default debug output.
-    #[allow(unused_variables)]
-    fn debug_foreign_def_id(
-        foreign_def_id: ForeignDefId<Self>,
-        fmt: &mut fmt::Formatter<'_>,
-    ) -> Option<fmt::Result> {
-        None
-    }
-
-    /// Prints the debug representation of an alias.
-    /// Returns `None` to fallback to the default debug output.
-    #[allow(unused_variables)]
-    fn debug_generator_id(
-        generator_id: GeneratorId<Self>,
-        fmt: &mut fmt::Formatter<'_>,
-    ) -> Option<fmt::Result> {
-        None
-    }
-
-    /// Prints the debug representation of an alias. To get good
-    /// results, this requires inspecting TLS, and is difficult to
-    /// code without reference to a specific interner (and hence
-    /// fully known types).
-    ///
-    /// Returns `None` to fallback to the default debug output (e.g.,
-    /// if no info about current program is available from TLS).
-    #[allow(unused_variables)]
-    fn debug_alias(alias: &AliasTy<Self>, fmt: &mut fmt::Formatter<'_>) -> Option<fmt::Result> {
-        None
-    }
-
-    /// Prints the debug representation of a ProjectionTy.
-    /// Returns `None` to fallback to the default debug output.
-    #[allow(unused_variables)]
-    fn debug_projection_ty(
-        projection_ty: &ProjectionTy<Self>,
-        fmt: &mut fmt::Formatter<'_>,
-    ) -> Option<fmt::Result> {
-        None
-    }
-
-    /// Prints the debug representation of an OpaqueTy.
-    /// Returns `None` to fallback to the default debug output.
-    #[allow(unused_variables)]
-    fn debug_opaque_ty(
-        opaque_ty: &OpaqueTy<Self>,
-        fmt: &mut fmt::Formatter<'_>,
-    ) -> Option<fmt::Result> {
-        None
-    }
-
-    /// Prints the debug representation of a type.
-    /// Returns `None` to fallback to the default debug output.
-    #[allow(unused_variables)]
-    fn debug_ty(ty: &Ty<Self>, fmt: &mut fmt::Formatter<'_>) -> Option<fmt::Result> {
-        None
-    }
-
-    /// Prints the debug representation of a lifetime.
-    /// Returns `None` to fallback to the default debug output.
-    #[allow(unused_variables)]
-    fn debug_lifetime(
-        lifetime: &Lifetime<Self>,
-        fmt: &mut fmt::Formatter<'_>,
-    ) -> Option<fmt::Result> {
-        None
-    }
-
-    /// Prints the debug representation of a const.
-    /// Returns `None` to fallback to the default debug output.
-    #[allow(unused_variables)]
-    fn debug_const(constant: &Const<Self>, fmt: &mut fmt::Formatter<'_>) -> Option<fmt::Result> {
-        None
-    }
-
-    /// Prints the debug representation of an parameter.
-    /// Returns `None` to fallback to the default debug output.
-    #[allow(unused_variables)]
-    fn debug_generic_arg(
-        generic_arg: &GenericArg<Self>,
-        fmt: &mut fmt::Formatter<'_>,
-    ) -> Option<fmt::Result> {
-        None
-    }
-
-    /// Prints the debug representation of a parameter kinds list.
-    /// Returns `None` to fallback to the default debug output.
-    #[allow(unused_variables)]
-    fn debug_variable_kinds(
-        variable_kinds: &VariableKinds<Self>,
-        fmt: &mut fmt::Formatter<'_>,
-    ) -> Option<fmt::Result> {
-        None
-    }
-
-    /// Prints the debug representation of a parameter kinds list, with angle brackets.
-    /// Returns `None` to fallback to the default debug output.
-    #[allow(unused_variables)]
-    fn debug_variable_kinds_with_angles(
-        variable_kinds: &VariableKinds<Self>,
-        fmt: &mut fmt::Formatter<'_>,
-    ) -> Option<fmt::Result> {
-        None
-    }
-
-    /// Prints the debug representation of an parameter kinds list with universe index.
-    /// Returns `None` to fallback to the default debug output.
-    #[allow(unused_variables)]
-    fn debug_canonical_var_kinds(
-        canonical_var_kinds: &CanonicalVarKinds<Self>,
-        fmt: &mut fmt::Formatter<'_>,
-    ) -> Option<fmt::Result> {
-        None
-    }
-
-    /// Prints the debug representation of an goal.
-    /// Returns `None` to fallback to the default debug output.
-    #[allow(unused_variables)]
-    fn debug_goal(goal: &Goal<Self>, fmt: &mut fmt::Formatter<'_>) -> Option<fmt::Result> {
-        None
-    }
-
-    /// Prints the debug representation of a list of goals.
-    /// Returns `None` to fallback to the default debug output.
-    #[allow(unused_variables)]
-    fn debug_goals(goals: &Goals<Self>, fmt: &mut fmt::Formatter<'_>) -> Option<fmt::Result> {
-        None
-    }
-
-    /// Prints the debug representation of a ProgramClauseImplication.
-    /// Returns `None` to fallback to the default debug output.
-    #[allow(unused_variables)]
-    fn debug_program_clause_implication(
-        pci: &ProgramClauseImplication<Self>,
-        fmt: &mut fmt::Formatter<'_>,
-    ) -> Option<fmt::Result> {
-        None
-    }
-
-    /// Prints the debug representation of a ProgramClause.
-    /// Returns `None` to fallback to the default debug output.
-    #[allow(unused_variables)]
-    fn debug_program_clause(
-        clause: &ProgramClause<Self>,
-        fmt: &mut fmt::Formatter<'_>,
-    ) -> Option<fmt::Result> {
-        None
-    }
-
-    /// Prints the debug representation of a ProgramClauses.
-    /// Returns `None` to fallback to the default debug output.
-    #[allow(unused_variables)]
-    fn debug_program_clauses(
-        clauses: &ProgramClauses<Self>,
-        fmt: &mut fmt::Formatter<'_>,
-    ) -> Option<fmt::Result> {
-        None
-    }
-
-    /// Prints the debug representation of a Substitution.
-    /// Returns `None` to fallback to the default debug output.
-    #[allow(unused_variables)]
-    fn debug_substitution(
-        substitution: &Substitution<Self>,
-        fmt: &mut fmt::Formatter<'_>,
-    ) -> Option<fmt::Result> {
-        None
-    }
-
-    /// Prints the debug representation of a SeparatorTraitRef.
-    /// Returns `None` to fallback to the default debug output.
-    #[allow(unused_variables)]
-    fn debug_separator_trait_ref(
-        separator_trait_ref: &SeparatorTraitRef<'_, Self>,
-        fmt: &mut fmt::Formatter<'_>,
-    ) -> Option<fmt::Result> {
-        None
-    }
-
-    /// Prints the debug representation of a QuantifiedWhereClauses.
-    /// Returns `None` to fallback to the default debug output.
-    #[allow(unused_variables)]
-    fn debug_quantified_where_clauses(
-        clauses: &QuantifiedWhereClauses<Self>,
-        fmt: &mut fmt::Formatter<'_>,
-    ) -> Option<fmt::Result> {
-        None
-    }
-
-    /// Prints the debug representation of a Constraints.
-    /// Returns `None` to fallback to the default debug output.
-    #[allow(unused_variables)]
-    fn debug_constraints(
-        clauses: &Constraints<Self>,
-        fmt: &mut fmt::Formatter<'_>,
-    ) -> Option<fmt::Result> {
-        None
-    }
-
-    /// Prints the debug representation of a Variances.
-    /// Returns `None` to fallback to the default debug output.
-    #[allow(unused_variables)]
-    fn debug_variances(
-        variances: &Variances<Self>,
-        fmt: &mut fmt::Formatter<'_>,
-    ) -> Option<fmt::Result> {
-        None
-    }
-
-    /// Create an "interned" type from `ty`. This is not normally
-    /// invoked directly; instead, you invoke `TyKind::intern` (which
-    /// will ultimately call this method).
-    fn intern_ty(self, kind: TyKind<Self>) -> Self::InternedType;
-
-    /// Lookup the `TyKind` from an interned type.
-    fn ty_data(self, ty: &Self::InternedType) -> &TyData<Self>;
-
-    /// Create an "interned" lifetime from `lifetime`. This is not
-    /// normally invoked directly; instead, you invoke
-    /// `LifetimeData::intern` (which will ultimately call this
-    /// method).
-    fn intern_lifetime(self, lifetime: LifetimeData<Self>) -> Self::InternedLifetime;
-
-    /// Lookup the `LifetimeData` that was interned to create a `InternedLifetime`.
-    fn lifetime_data(self, lifetime: &Self::InternedLifetime) -> &LifetimeData<Self>;
-
-    /// Create an "interned" const from `const`. This is not
-    /// normally invoked directly; instead, you invoke
-    /// `ConstData::intern` (which will ultimately call this
-    /// method).
-    fn intern_const(self, constant: ConstData<Self>) -> Self::InternedConst;
-
-    /// Lookup the `ConstData` that was interned to create a `InternedConst`.
-    fn const_data(self, constant: &Self::InternedConst) -> &ConstData<Self>;
-
-    /// Determine whether two concrete const values are equal.
-    fn const_eq(
-        self,
-        ty: &Self::InternedType,
-        c1: &Self::InternedConcreteConst,
-        c2: &Self::InternedConcreteConst,
-    ) -> bool;
-
-    /// Create an "interned" parameter from `data`. This is not
-    /// normally invoked directly; instead, you invoke
-    /// `GenericArgData::intern` (which will ultimately call this
-    /// method).
-    fn intern_generic_arg(self, data: GenericArgData<Self>) -> Self::InternedGenericArg;
-
-    /// Lookup the `LifetimeData` that was interned to create a `InternedLifetime`.
-    fn generic_arg_data(self, lifetime: &Self::InternedGenericArg) -> &GenericArgData<Self>;
-
-    /// Create an "interned" goal from `data`. This is not
-    /// normally invoked directly; instead, you invoke
-    /// `GoalData::intern` (which will ultimately call this
-    /// method).
-    fn intern_goal(self, data: GoalData<Self>) -> Self::InternedGoal;
-
-    /// Lookup the `GoalData` that was interned to create a `InternedGoal`.
-    fn goal_data(self, goal: &Self::InternedGoal) -> &GoalData<Self>;
-
-    /// Create an "interned" goals from `data`. This is not
-    /// normally invoked directly; instead, you invoke
-    /// `GoalsData::intern` (which will ultimately call this
-    /// method).
-    fn intern_goals<E>(
-        self,
-        data: impl IntoIterator<Item = Result<Goal<Self>, E>>,
-    ) -> Result<Self::InternedGoals, E>;
-
-    /// Lookup the `GoalsData` that was interned to create a `InternedGoals`.
-    fn goals_data(self, goals: &Self::InternedGoals) -> &[Goal<Self>];
-
-    /// Create an "interned" substitution from `data`. This is not
-    /// normally invoked directly; instead, you invoke
-    /// `SubstitutionData::intern` (which will ultimately call this
-    /// method).
-    fn intern_substitution<E>(
-        self,
-        data: impl IntoIterator<Item = Result<GenericArg<Self>, E>>,
-    ) -> Result<Self::InternedSubstitution, E>;
-
-    /// Lookup the `SubstitutionData` that was interned to create a `InternedSubstitution`.
-    fn substitution_data(self, substitution: &Self::InternedSubstitution) -> &[GenericArg<Self>];
-
-    /// Create an "interned" program clause from `data`. This is not
-    /// normally invoked directly; instead, you invoke
-    /// `ProgramClauseData::intern` (which will ultimately call this
-    /// method).
-    fn intern_program_clause(self, data: ProgramClauseData<Self>) -> Self::InternedProgramClause;
-
-    /// Lookup the `ProgramClauseData` that was interned to create a `ProgramClause`.
-    fn program_clause_data(self, clause: &Self::InternedProgramClause) -> &ProgramClauseData<Self>;
-
-    /// Create an "interned" program clauses from `data`. This is not
-    /// normally invoked directly; instead, you invoke
-    /// `ProgramClauses::from_iter` (which will ultimately call this
-    /// method).
-    fn intern_program_clauses<E>(
-        self,
-        data: impl IntoIterator<Item = Result<ProgramClause<Self>, E>>,
-    ) -> Result<Self::InternedProgramClauses, E>;
-
-    /// Lookup the `ProgramClauseData` that was interned to create a `ProgramClause`.
-    fn program_clauses_data(self, clauses: &Self::InternedProgramClauses)
-        -> &[ProgramClause<Self>];
-
-    /// Create an "interned" quantified where clauses from `data`. This is not
-    /// normally invoked directly; instead, you invoke
-    /// `QuantifiedWhereClauses::from_iter` (which will ultimately call this
-    /// method).
-    fn intern_quantified_where_clauses<E>(
-        self,
-        data: impl IntoIterator<Item = Result<QuantifiedWhereClause<Self>, E>>,
-    ) -> Result<Self::InternedQuantifiedWhereClauses, E>;
-
-    /// Lookup the slice of `QuantifiedWhereClause` that was interned to
-    /// create a `QuantifiedWhereClauses`.
-    fn quantified_where_clauses_data(
-        self,
-        clauses: &Self::InternedQuantifiedWhereClauses,
-    ) -> &[QuantifiedWhereClause<Self>];
-
-    /// Create an "interned" parameter kinds from `data`. This is not
-    /// normally invoked directly; instead, you invoke
-    /// `VariableKinds::from_iter` (which will ultimately call this
-    /// method).
-    fn intern_generic_arg_kinds<E>(
-        self,
-        data: impl IntoIterator<Item = Result<VariableKind<Self>, E>>,
-    ) -> Result<Self::InternedVariableKinds, E>;
-
-    /// Lookup the slice of `VariableKinds` that was interned to
-    /// create a `VariableKinds`.
-    fn variable_kinds_data(
-        self,
-        variable_kinds: &Self::InternedVariableKinds,
-    ) -> &[VariableKind<Self>];
-
-    /// Create "interned" variable kinds with universe index from `data`. This is not
-    /// normally invoked directly; instead, you invoke
-    /// `CanonicalVarKinds::from_iter` (which will ultimately call this
-    /// method).
-    fn intern_canonical_var_kinds<E>(
-        self,
-        data: impl IntoIterator<Item = Result<CanonicalVarKind<Self>, E>>,
-    ) -> Result<Self::InternedCanonicalVarKinds, E>;
-
-    /// Lookup the slice of `CanonicalVariableKind` that was interned to
-    /// create a `CanonicalVariableKinds`.
-    fn canonical_var_kinds_data(
-        self,
-        canonical_var_kinds: &Self::InternedCanonicalVarKinds,
-    ) -> &[CanonicalVarKind<Self>];
-
-    /// Create "interned" constraints from `data`. This is not
-    /// normally invoked dirctly; instead, you invoke
-    /// `Constraints::from_iter` (which will ultimately call this
-    /// method).
-    fn intern_constraints<E>(
-        self,
-        data: impl IntoIterator<Item = Result<InEnvironment<Constraint<Self>>, E>>,
-    ) -> Result<Self::InternedConstraints, E>;
-
-    /// Lookup the slice of `Constraint` that was interned to
-    /// create a `Constraints`.
-    fn constraints_data(
-        self,
-        constraints: &Self::InternedConstraints,
-    ) -> &[InEnvironment<Constraint<Self>>];
-
-    /// Create "interned" variances from `data`. This is not
-    /// normally invoked directly; instead, you invoke
-    /// `Variances::from` (which will ultimately call this
-    /// method).
-    fn intern_variances<E>(
-        self,
-        data: impl IntoIterator<Item = Result<Variance, E>>,
-    ) -> Result<Self::InternedVariances, E>;
-
-    /// Lookup the slice of `Variance` that was interned to
-    /// create a `Variances`.
-    fn variances_data(self, variances: &Self::InternedVariances) -> &[Variance];
-}
-
-/// Implemented by types that have an associated interner (which
-/// are virtually all of the types in chalk-ir, for example).
-/// This lets us map from a type like `Ty<I>` to the parameter `I`.
-///
-/// It's particularly useful for writing `TypeFoldable` impls for generic types like
-/// `Binder<T>`, since it allows us to figure out the interner of `T`.
-pub trait HasInterner {
-    /// The interner associated with the type.
-    type Interner: Interner;
-}
-
-impl<T: HasInterner> HasInterner for [T] {
-    type Interner = T::Interner;
-}
-
-impl<T: HasInterner> HasInterner for Vec<T> {
-    type Interner = T::Interner;
-}
-
-impl<T: HasInterner> HasInterner for Box<T> {
-    type Interner = T::Interner;
-}
-
-impl<T: HasInterner> HasInterner for Arc<T> {
-    type Interner = T::Interner;
-}
-
-impl<T: HasInterner + ?Sized> HasInterner for &T {
-    type Interner = T::Interner;
-}
-
-impl<I: Interner> HasInterner for PhantomData<I> {
-    type Interner = I;
-}
-
-impl<A, B, I> HasInterner for (A, B)
-where
-    A: HasInterner<Interner = I>,
-    B: HasInterner<Interner = I>,
-    I: Interner,
-{
-    type Interner = I;
-}
-
-impl<A, B, C, I> HasInterner for (A, B, C)
-where
-    A: HasInterner<Interner = I>,
-    B: HasInterner<Interner = I>,
-    C: HasInterner<Interner = I>,
-    I: Interner,
-{
-    type Interner = I;
-}
-
-impl<'a, T: HasInterner> HasInterner for std::slice::Iter<'a, T> {
-    type Interner = T::Interner;
-}
diff --git a/vendor/chalk-ir/src/lib.rs b/vendor/chalk-ir/src/lib.rs
deleted file mode 100644
index 5cf44b0c3..000000000
--- a/vendor/chalk-ir/src/lib.rs
+++ /dev/null
@@ -1,3055 +0,0 @@
-//! Defines the IR for types and logical predicates.
-
-#![deny(rust_2018_idioms)]
-#![warn(missing_docs)]
-
-// Allows macros to refer to this crate as `::chalk_ir`
-extern crate self as chalk_ir;
-
-use crate::cast::{Cast, CastTo, Caster};
-use crate::fold::shift::Shift;
-use crate::fold::{FallibleTypeFolder, Subst, TypeFoldable, TypeFolder, TypeSuperFoldable};
-use crate::visit::{TypeSuperVisitable, TypeVisitable, TypeVisitor, VisitExt};
-use chalk_derive::{
-    FallibleTypeFolder, HasInterner, TypeFoldable, TypeSuperVisitable, TypeVisitable, Zip,
-};
-use std::marker::PhantomData;
-use std::ops::ControlFlow;
-
-pub use crate::debug::SeparatorTraitRef;
-#[macro_use(bitflags)]
-extern crate bitflags;
-/// Uninhabited (empty) type, used in combination with `PhantomData`.
-#[derive(Debug, Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash)]
-pub enum Void {}
-
-/// Many of our internal operations (e.g., unification) are an attempt
-/// to perform some operation which may not complete.
-pub type Fallible<T> = Result<T, NoSolution>;
-
-/// A combination of `Fallible` and `Floundered`.
-pub enum FallibleOrFloundered<T> {
-    /// Success
-    Ok(T),
-    /// No solution. See `chalk_ir::NoSolution`.
-    NoSolution,
-    /// Floundered. See `chalk_ir::Floundered`.
-    Floundered,
-}
-
-/// Indicates that the attempted operation has "no solution" -- i.e.,
-/// cannot be performed.
-#[derive(Copy, Clone, Debug, PartialEq, Eq, PartialOrd, Ord, Hash)]
-pub struct NoSolution;
-
-/// Indicates that the complete set of program clauses for this goal
-/// cannot be enumerated.
-pub struct Floundered;
-
-macro_rules! impl_debugs {
-    ($($id:ident), *) => {
-        $(
-            impl<I: Interner> std::fmt::Debug for $id<I> {
-                fn fmt(&self, fmt: &mut std::fmt::Formatter<'_>) -> Result<(), std::fmt::Error> {
-                    write!(fmt, "{}({:?})", stringify!($id), self.0)
-                }
-            }
-        )*
-    };
-}
-
-#[macro_use]
-pub mod zip;
-
-#[macro_use]
-pub mod fold;
-
-#[macro_use]
-pub mod visit;
-
-pub mod cast;
-
-pub mod interner;
-use interner::{HasInterner, Interner};
-
-pub mod could_match;
-pub mod debug;
-
-/// Variance
-#[derive(Copy, Clone, Debug, PartialEq, Eq, Hash)]
-pub enum Variance {
-    /// a <: b
-    Covariant,
-    /// a == b
-    Invariant,
-    /// b <: a
-    Contravariant,
-}
-
-impl Variance {
-    /// `a.xform(b)` combines the variance of a context with the
-    /// variance of a type with the following meaning. If we are in a
-    /// context with variance `a`, and we encounter a type argument in
-    /// a position with variance `b`, then `a.xform(b)` is the new
-    /// variance with which the argument appears.
-    ///
-    /// Example 1:
-    ///
-    /// ```ignore
-    /// *mut Vec<i32>
-    /// ```
-    ///
-    /// Here, the "ambient" variance starts as covariant. `*mut T` is
-    /// invariant with respect to `T`, so the variance in which the
-    /// `Vec<i32>` appears is `Covariant.xform(Invariant)`, which
-    /// yields `Invariant`. Now, the type `Vec<T>` is covariant with
-    /// respect to its type argument `T`, and hence the variance of
-    /// the `i32` here is `Invariant.xform(Covariant)`, which results
-    /// (again) in `Invariant`.
-    ///
-    /// Example 2:
-    ///
-    /// ```ignore
-    /// fn(*const Vec<i32>, *mut Vec<i32)
-    /// ```
-    ///
-    /// The ambient variance is covariant. A `fn` type is
-    /// contravariant with respect to its parameters, so the variance
-    /// within which both pointer types appear is
-    /// `Covariant.xform(Contravariant)`, or `Contravariant`. `*const
-    /// T` is covariant with respect to `T`, so the variance within
-    /// which the first `Vec<i32>` appears is
-    /// `Contravariant.xform(Covariant)` or `Contravariant`. The same
-    /// is true for its `i32` argument. In the `*mut T` case, the
-    /// variance of `Vec<i32>` is `Contravariant.xform(Invariant)`,
-    /// and hence the outermost type is `Invariant` with respect to
-    /// `Vec<i32>` (and its `i32` argument).
-    ///
-    /// Source: Figure 1 of "Taming the Wildcards:
-    /// Combining Definition- and Use-Site Variance" published in PLDI'11.
-    /// (Doc from rustc)
-    pub fn xform(self, other: Variance) -> Variance {
-        match (self, other) {
-            (Variance::Invariant, _) => Variance::Invariant,
-            (_, Variance::Invariant) => Variance::Invariant,
-            (_, Variance::Covariant) => self,
-            (Variance::Covariant, Variance::Contravariant) => Variance::Contravariant,
-            (Variance::Contravariant, Variance::Contravariant) => Variance::Covariant,
-        }
-    }
-
-    /// Converts `Covariant` into `Contravariant` and vice-versa. `Invariant`
-    /// stays the same.
-    pub fn invert(self) -> Variance {
-        match self {
-            Variance::Invariant => Variance::Invariant,
-            Variance::Covariant => Variance::Contravariant,
-            Variance::Contravariant => Variance::Covariant,
-        }
-    }
-}
-
-#[derive(Clone, PartialEq, Eq, Hash, TypeFoldable, TypeVisitable, HasInterner)]
-/// The set of assumptions we've made so far, and the current number of
-/// universal (forall) quantifiers we're within.
-pub struct Environment<I: Interner> {
-    /// The clauses in the environment.
-    pub clauses: ProgramClauses<I>,
-}
-
-impl<I: Interner> Copy for Environment<I> where I::InternedProgramClauses: Copy {}
-
-impl<I: Interner> Environment<I> {
-    /// Creates a new environment.
-    pub fn new(interner: I) -> Self {
-        Environment {
-            clauses: ProgramClauses::empty(interner),
-        }
-    }
-
-    /// Adds (an iterator of) clauses to the environment.
-    pub fn add_clauses<II>(&self, interner: I, clauses: II) -> Self
-    where
-        II: IntoIterator<Item = ProgramClause<I>>,
-    {
-        let mut env = self.clone();
-        env.clauses =
-            ProgramClauses::from_iter(interner, env.clauses.iter(interner).cloned().chain(clauses));
-        env
-    }
-
-    /// True if any of the clauses in the environment have a consequence of `Compatible`.
-    /// Panics if the conditions or constraints of that clause are not empty.
-    pub fn has_compatible_clause(&self, interner: I) -> bool {
-        self.clauses.as_slice(interner).iter().any(|c| {
-            let ProgramClauseData(implication) = c.data(interner);
-            match implication.skip_binders().consequence {
-                DomainGoal::Compatible => {
-                    // We currently don't generate `Compatible` with any conditions or constraints
-                    // If this was needed, for whatever reason, then a third "yes, but must evaluate"
-                    // return value would have to be added.
-                    assert!(implication.skip_binders().conditions.is_empty(interner));
-                    assert!(implication.skip_binders().constraints.is_empty(interner));
-                    true
-                }
-                _ => false,
-            }
-        })
-    }
-}
-
-/// A goal with an environment to solve it in.
-#[derive(Clone, Debug, PartialEq, Eq, Hash, TypeFoldable, TypeVisitable)]
-#[allow(missing_docs)]
-pub struct InEnvironment<G: HasInterner> {
-    pub environment: Environment<G::Interner>,
-    pub goal: G,
-}
-
-impl<G: HasInterner<Interner = I> + Copy, I: Interner> Copy for InEnvironment<G> where
-    I::InternedProgramClauses: Copy
-{
-}
-
-impl<G: HasInterner> InEnvironment<G> {
-    /// Creates a new environment/goal pair.
-    pub fn new(environment: &Environment<G::Interner>, goal: G) -> Self {
-        InEnvironment {
-            environment: environment.clone(),
-            goal,
-        }
-    }
-
-    /// Maps the goal without touching the environment.
-    pub fn map<OP, H>(self, op: OP) -> InEnvironment<H>
-    where
-        OP: FnOnce(G) -> H,
-        H: HasInterner<Interner = G::Interner>,
-    {
-        InEnvironment {
-            environment: self.environment,
-            goal: op(self.goal),
-        }
-    }
-}
-
-impl<G: HasInterner> HasInterner for InEnvironment<G> {
-    type Interner = G::Interner;
-}
-
-/// Different signed int types.
-#[derive(Copy, Clone, Debug, PartialEq, Eq, PartialOrd, Ord, Hash)]
-#[allow(missing_docs)]
-pub enum IntTy {
-    Isize,
-    I8,
-    I16,
-    I32,
-    I64,
-    I128,
-}
-
-/// Different unsigned int types.
-#[derive(Copy, Clone, Debug, PartialEq, Eq, PartialOrd, Ord, Hash)]
-#[allow(missing_docs)]
-pub enum UintTy {
-    Usize,
-    U8,
-    U16,
-    U32,
-    U64,
-    U128,
-}
-
-/// Different kinds of float types.
-#[derive(Copy, Clone, Debug, PartialEq, Eq, PartialOrd, Ord, Hash)]
-#[allow(missing_docs)]
-pub enum FloatTy {
-    F32,
-    F64,
-}
-
-/// Types of scalar values.
-#[derive(Copy, Clone, Debug, PartialEq, Eq, PartialOrd, Ord, Hash)]
-#[allow(missing_docs)]
-pub enum Scalar {
-    Bool,
-    Char,
-    Int(IntTy),
-    Uint(UintTy),
-    Float(FloatTy),
-}
-
-/// Whether a function is safe or not.
-#[derive(Copy, Clone, Debug, PartialEq, Eq, PartialOrd, Ord, Hash)]
-pub enum Safety {
-    /// Safe
-    Safe,
-    /// Unsafe
-    Unsafe,
-}
-
-/// Whether a type is mutable or not.
-#[derive(Copy, Clone, Debug, PartialEq, Eq, PartialOrd, Ord, Hash)]
-pub enum Mutability {
-    /// Mutable
-    Mut,
-    /// Immutable
-    Not,
-}
-
-/// An universe index is how a universally quantified parameter is
-/// represented when it's binder is moved into the environment.
-/// An example chain of transformations would be:
-/// `forall<T> { Goal(T) }` (syntactical representation)
-/// `forall { Goal(?0) }` (used a DeBruijn index)
-/// `Goal(!U1)` (the quantifier was moved to the environment and replaced with a universe index)
-/// See <https://rustc-dev-guide.rust-lang.org/borrow_check/region_inference.html#placeholders-and-universes> for more.
-#[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash)]
-pub struct UniverseIndex {
-    /// The counter for the universe index, starts with 0.
-    pub counter: usize,
-}
-
-impl UniverseIndex {
-    /// Root universe index (0).
-    pub const ROOT: UniverseIndex = UniverseIndex { counter: 0 };
-
-    /// Root universe index (0).
-    pub fn root() -> UniverseIndex {
-        Self::ROOT
-    }
-
-    /// Whether one universe can "see" another.
-    pub fn can_see(self, ui: UniverseIndex) -> bool {
-        self.counter >= ui.counter
-    }
-
-    /// Increases the index counter.
-    pub fn next(self) -> UniverseIndex {
-        UniverseIndex {
-            counter: self.counter + 1,
-        }
-    }
-}
-
-/// Maps the universes found in the `u_canonicalize` result (the
-/// "canonical" universes) to the universes found in the original
-/// value (and vice versa). When used as a folder -- i.e., from
-/// outside this module -- converts from "canonical" universes to the
-/// original (but see the `UMapToCanonical` folder).
-#[derive(Clone, Debug)]
-pub struct UniverseMap {
-    /// A reverse map -- for each universe Ux that appears in
-    /// `quantified`, the corresponding universe in the original was
-    /// `universes[x]`.
-    pub universes: Vec<UniverseIndex>,
-}
-
-impl UniverseMap {
-    /// Creates a new universe map.
-    pub fn new() -> Self {
-        UniverseMap {
-            universes: vec![UniverseIndex::root()],
-        }
-    }
-
-    /// Number of canonical universes.
-    pub fn num_canonical_universes(&self) -> usize {
-        self.universes.len()
-    }
-}
-
-/// The id for an Abstract Data Type (i.e. structs, unions and enums).
-#[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash)]
-pub struct AdtId<I: Interner>(pub I::InternedAdtId);
-
-/// The id of a trait definition; could be used to load the trait datum by
-/// invoking the [`trait_datum`] method.
-///
-/// [`trait_datum`]: ../chalk_solve/trait.RustIrDatabase.html#tymethod.trait_datum
-#[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash)]
-pub struct TraitId<I: Interner>(pub I::DefId);
-
-/// The id for an impl.
-#[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash)]
-pub struct ImplId<I: Interner>(pub I::DefId);
-
-/// Id for a specific clause.
-#[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash)]
-pub struct ClauseId<I: Interner>(pub I::DefId);
-
-/// The id for the associated type member of a trait. The details of the type
-/// can be found by invoking the [`associated_ty_data`] method.
-///
-/// [`associated_ty_data`]: ../chalk_solve/trait.RustIrDatabase.html#tymethod.associated_ty_data
-#[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash)]
-pub struct AssocTypeId<I: Interner>(pub I::DefId);
-
-/// Id for an opaque type.
-#[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash)]
-pub struct OpaqueTyId<I: Interner>(pub I::DefId);
-
-/// Function definition id.
-#[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash)]
-pub struct FnDefId<I: Interner>(pub I::DefId);
-
-/// Id for Rust closures.
-#[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash)]
-pub struct ClosureId<I: Interner>(pub I::DefId);
-
-/// Id for Rust generators.
-#[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash)]
-pub struct GeneratorId<I: Interner>(pub I::DefId);
-
-/// Id for foreign types.
-#[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash)]
-pub struct ForeignDefId<I: Interner>(pub I::DefId);
-
-impl_debugs!(ImplId, ClauseId);
-
-/// A Rust type. The actual type data is stored in `TyKind`.
-#[derive(Copy, Clone, PartialEq, Eq, Hash, PartialOrd, Ord, HasInterner)]
-pub struct Ty<I: Interner> {
-    interned: I::InternedType,
-}
-
-impl<I: Interner> Ty<I> {
-    /// Creates a type from `TyKind`.
-    pub fn new(interner: I, data: impl CastTo<TyKind<I>>) -> Self {
-        let ty_kind = data.cast(interner);
-        Ty {
-            interned: I::intern_ty(interner, ty_kind),
-        }
-    }
-
-    /// Gets the interned type.
-    pub fn interned(&self) -> &I::InternedType {
-        &self.interned
-    }
-
-    /// Gets the underlying type data.
-    pub fn data(&self, interner: I) -> &TyData<I> {
-        I::ty_data(interner, &self.interned)
-    }
-
-    /// Gets the underlying type kind.
-    pub fn kind(&self, interner: I) -> &TyKind<I> {
-        &I::ty_data(interner, &self.interned).kind
-    }
-
-    /// Creates a `FromEnv` constraint using this type.
-    pub fn from_env(&self) -> FromEnv<I> {
-        FromEnv::Ty(self.clone())
-    }
-
-    /// Creates a WF-constraint for this type.
-    pub fn well_formed(&self) -> WellFormed<I> {
-        WellFormed::Ty(self.clone())
-    }
-
-    /// Creates a domain goal `FromEnv(T)` where `T` is this type.
-    pub fn into_from_env_goal(self, interner: I) -> DomainGoal<I> {
-        self.from_env().cast(interner)
-    }
-
-    /// If this is a `TyKind::BoundVar(d)`, returns `Some(d)` else `None`.
-    pub fn bound_var(&self, interner: I) -> Option<BoundVar> {
-        if let TyKind::BoundVar(bv) = self.kind(interner) {
-            Some(*bv)
-        } else {
-            None
-        }
-    }
-
-    /// If this is a `TyKind::InferenceVar(d)`, returns `Some(d)` else `None`.
-    pub fn inference_var(&self, interner: I) -> Option<InferenceVar> {
-        if let TyKind::InferenceVar(depth, _) = self.kind(interner) {
-            Some(*depth)
-        } else {
-            None
-        }
-    }
-
-    /// Returns true if this is a `BoundVar` or an `InferenceVar` of `TyVariableKind::General`.
-    pub fn is_general_var(&self, interner: I, binders: &CanonicalVarKinds<I>) -> bool {
-        match self.kind(interner) {
-            TyKind::BoundVar(bv)
-                if bv.debruijn == DebruijnIndex::INNERMOST
-                    && binders.at(interner, bv.index).kind
-                        == VariableKind::Ty(TyVariableKind::General) =>
-            {
-                true
-            }
-            TyKind::InferenceVar(_, TyVariableKind::General) => true,
-            _ => false,
-        }
-    }
-
-    /// Returns true if this is an `Alias`.
-    pub fn is_alias(&self, interner: I) -> bool {
-        matches!(self.kind(interner), TyKind::Alias(..))
-    }
-
-    /// Returns true if this is an `IntTy` or `UintTy`.
-    pub fn is_integer(&self, interner: I) -> bool {
-        matches!(
-            self.kind(interner),
-            TyKind::Scalar(Scalar::Int(_) | Scalar::Uint(_))
-        )
-    }
-
-    /// Returns true if this is a `FloatTy`.
-    pub fn is_float(&self, interner: I) -> bool {
-        matches!(self.kind(interner), TyKind::Scalar(Scalar::Float(_)))
-    }
-
-    /// Returns `Some(adt_id)` if this is an ADT, `None` otherwise
-    pub fn adt_id(&self, interner: I) -> Option<AdtId<I>> {
-        match self.kind(interner) {
-            TyKind::Adt(adt_id, _) => Some(*adt_id),
-            _ => None,
-        }
-    }
-
-    /// True if this type contains "bound" types/lifetimes, and hence
-    /// needs to be shifted across binders. This is a very inefficient
-    /// check, intended only for debug assertions, because I am lazy.
-    pub fn needs_shift(&self, interner: I) -> bool {
-        self.has_free_vars(interner)
-    }
-}
-
-/// Contains the data for a Ty
-#[derive(Clone, PartialEq, Eq, Hash, HasInterner)]
-pub struct TyData<I: Interner> {
-    /// The kind
-    pub kind: TyKind<I>,
-    /// Type flags
-    pub flags: TypeFlags,
-}
-
-bitflags! {
-    /// Contains flags indicating various properties of a Ty
-    pub struct TypeFlags : u16 {
-        /// Does the type contain an InferenceVar
-        const HAS_TY_INFER                = 1;
-        /// Does the type contain a lifetime with an InferenceVar
-        const HAS_RE_INFER                = 1 << 1;
-        /// Does the type contain a ConstValue with an InferenceVar
-        const HAS_CT_INFER                = 1 << 2;
-        /// Does the type contain a Placeholder TyKind
-        const HAS_TY_PLACEHOLDER          = 1 << 3;
-        /// Does the type contain a lifetime with a Placeholder
-        const HAS_RE_PLACEHOLDER          = 1 << 4;
-        /// Does the type contain a ConstValue Placeholder
-        const HAS_CT_PLACEHOLDER          = 1 << 5;
-        /// True when the type has free lifetimes related to a local context
-        const HAS_FREE_LOCAL_REGIONS      = 1 << 6;
-        /// Does the type contain a projection of an associated type
-        const HAS_TY_PROJECTION           = 1 << 7;
-        /// Does the type contain an opaque type
-        const HAS_TY_OPAQUE               = 1 << 8;
-        /// Does the type contain an unevaluated const projection
-        const HAS_CT_PROJECTION           = 1 << 9;
-        /// Does the type contain an error
-        const HAS_ERROR                   = 1 << 10;
-        /// Does the type contain any free lifetimes
-        const HAS_FREE_REGIONS            = 1 << 11;
-        /// True when the type contains lifetimes that will be substituted when function is called
-        const HAS_RE_LATE_BOUND           = 1 << 12;
-        /// True when the type contains an erased lifetime
-        const HAS_RE_ERASED               = 1 << 13;
-        /// Does the type contain placeholders or inference variables that could be replaced later
-        const STILL_FURTHER_SPECIALIZABLE = 1 << 14;
-
-        /// True when the type contains free names local to a particular context
-        const HAS_FREE_LOCAL_NAMES        = TypeFlags::HAS_TY_INFER.bits
-                                          | TypeFlags::HAS_CT_INFER.bits
-                                          | TypeFlags::HAS_TY_PLACEHOLDER.bits
-                                          | TypeFlags::HAS_CT_PLACEHOLDER.bits
-                                          | TypeFlags::HAS_FREE_LOCAL_REGIONS.bits;
-
-        /// Does the type contain any form of projection
-        const HAS_PROJECTION              = TypeFlags::HAS_TY_PROJECTION.bits
-                                          | TypeFlags::HAS_TY_OPAQUE.bits
-                                          | TypeFlags::HAS_CT_PROJECTION.bits;
-    }
-}
-/// Type data, which holds the actual type information.
-#[derive(Clone, PartialEq, Eq, Hash, HasInterner)]
-pub enum TyKind<I: Interner> {
-    /// Abstract data types, i.e., structs, unions, or enumerations.
-    /// For example, a type like `Vec<T>`.
-    Adt(AdtId<I>, Substitution<I>),
-
-    /// an associated type like `Iterator::Item`; see `AssociatedType` for details
-    AssociatedType(AssocTypeId<I>, Substitution<I>),
-
-    /// a scalar type like `bool` or `u32`
-    Scalar(Scalar),
-
-    /// a tuple of the given arity
-    Tuple(usize, Substitution<I>),
-
-    /// an array type like `[T; N]`
-    Array(Ty<I>, Const<I>),
-
-    /// a slice type like `[T]`
-    Slice(Ty<I>),
-
-    /// a raw pointer type like `*const T` or `*mut T`
-    Raw(Mutability, Ty<I>),
-
-    /// a reference type like `&T` or `&mut T`
-    Ref(Mutability, Lifetime<I>, Ty<I>),
-
-    /// a placeholder for opaque types like `impl Trait`
-    OpaqueType(OpaqueTyId<I>, Substitution<I>),
-
-    /// a function definition
-    FnDef(FnDefId<I>, Substitution<I>),
-
-    /// the string primitive type
-    Str,
-
-    /// the never type `!`
-    Never,
-
-    /// A closure.
-    Closure(ClosureId<I>, Substitution<I>),
-
-    /// A generator.
-    Generator(GeneratorId<I>, Substitution<I>),
-
-    /// A generator witness.
-    GeneratorWitness(GeneratorId<I>, Substitution<I>),
-
-    /// foreign types
-    Foreign(ForeignDefId<I>),
-
-    /// This can be used to represent an error, e.g. during name resolution of a type.
-    /// Chalk itself will not produce this, just pass it through when given.
-    Error,
-
-    /// instantiated from a universally quantified type, e.g., from
-    /// `forall<T> { .. }`. Stands in as a representative of "some
-    /// unknown type".
-    Placeholder(PlaceholderIndex),
-
-    /// A "dyn" type is a trait object type created via the "dyn Trait" syntax.
-    /// In the chalk parser, the traits that the object represents is parsed as
-    /// a QuantifiedInlineBound, and is then changed to a list of where clauses
-    /// during lowering.
-    ///
-    /// See the `Opaque` variant for a discussion about the use of
-    /// binders here.
-    Dyn(DynTy<I>),
-
-    /// An "alias" type represents some form of type alias, such as:
-    /// - An associated type projection like `<T as Iterator>::Item`
-    /// - `impl Trait` types
-    /// - Named type aliases like `type Foo<X> = Vec<X>`
-    Alias(AliasTy<I>),
-
-    /// A function type such as `for<'a> fn(&'a u32)`.
-    /// Note that "higher-ranked" types (starting with `for<>`) are either
-    /// function types or dyn types, and do not appear otherwise in Rust
-    /// surface syntax.
-    Function(FnPointer<I>),
-
-    /// References the binding at the given depth. The index is a [de
-    /// Bruijn index], so it counts back through the in-scope binders.
-    BoundVar(BoundVar),
-
-    /// Inference variable defined in the current inference context.
-    InferenceVar(InferenceVar, TyVariableKind),
-}
-
-impl<I: Interner> Copy for TyKind<I>
-where
-    I::InternedLifetime: Copy,
-    I::InternedSubstitution: Copy,
-    I::InternedVariableKinds: Copy,
-    I::InternedQuantifiedWhereClauses: Copy,
-    I::InternedType: Copy,
-    I::InternedConst: Copy,
-{
-}
-
-impl<I: Interner> TyKind<I> {
-    /// Casts the type data to a type.
-    pub fn intern(self, interner: I) -> Ty<I> {
-        Ty::new(interner, self)
-    }
-
-    /// Compute type flags for a TyKind
-    pub fn compute_flags(&self, interner: I) -> TypeFlags {
-        match self {
-            TyKind::Adt(_, substitution)
-            | TyKind::AssociatedType(_, substitution)
-            | TyKind::Tuple(_, substitution)
-            | TyKind::Closure(_, substitution)
-            | TyKind::Generator(_, substitution)
-            | TyKind::GeneratorWitness(_, substitution)
-            | TyKind::FnDef(_, substitution)
-            | TyKind::OpaqueType(_, substitution) => substitution.compute_flags(interner),
-            TyKind::Scalar(_) | TyKind::Str | TyKind::Never | TyKind::Foreign(_) => {
-                TypeFlags::empty()
-            }
-            TyKind::Error => TypeFlags::HAS_ERROR,
-            TyKind::Slice(ty) | TyKind::Raw(_, ty) => ty.data(interner).flags,
-            TyKind::Ref(_, lifetime, ty) => {
-                lifetime.compute_flags(interner) | ty.data(interner).flags
-            }
-            TyKind::Array(ty, const_ty) => {
-                let flags = ty.data(interner).flags;
-                let const_data = const_ty.data(interner);
-                flags
-                    | const_data.ty.data(interner).flags
-                    | match const_data.value {
-                        ConstValue::BoundVar(_) | ConstValue::Concrete(_) => TypeFlags::empty(),
-                        ConstValue::InferenceVar(_) => {
-                            TypeFlags::HAS_CT_INFER | TypeFlags::STILL_FURTHER_SPECIALIZABLE
-                        }
-                        ConstValue::Placeholder(_) => {
-                            TypeFlags::HAS_CT_PLACEHOLDER | TypeFlags::STILL_FURTHER_SPECIALIZABLE
-                        }
-                    }
-            }
-            TyKind::Placeholder(_) => TypeFlags::HAS_TY_PLACEHOLDER,
-            TyKind::Dyn(dyn_ty) => {
-                let lifetime_flags = dyn_ty.lifetime.compute_flags(interner);
-                let mut dyn_flags = TypeFlags::empty();
-                for var_kind in dyn_ty.bounds.skip_binders().iter(interner) {
-                    match &(var_kind.skip_binders()) {
-                        WhereClause::Implemented(trait_ref) => {
-                            dyn_flags |= trait_ref.substitution.compute_flags(interner)
-                        }
-                        WhereClause::AliasEq(alias_eq) => {
-                            dyn_flags |= alias_eq.alias.compute_flags(interner);
-                            dyn_flags |= alias_eq.ty.data(interner).flags;
-                        }
-                        WhereClause::LifetimeOutlives(lifetime_outlives) => {
-                            dyn_flags |= lifetime_outlives.a.compute_flags(interner)
-                                | lifetime_outlives.b.compute_flags(interner);
-                        }
-                        WhereClause::TypeOutlives(type_outlives) => {
-                            dyn_flags |= type_outlives.ty.data(interner).flags;
-                            dyn_flags |= type_outlives.lifetime.compute_flags(interner);
-                        }
-                    }
-                }
-                lifetime_flags | dyn_flags
-            }
-            TyKind::Alias(alias_ty) => alias_ty.compute_flags(interner),
-            TyKind::BoundVar(_) => TypeFlags::empty(),
-            TyKind::InferenceVar(_, _) => TypeFlags::HAS_TY_INFER,
-            TyKind::Function(fn_pointer) => fn_pointer.substitution.0.compute_flags(interner),
-        }
-    }
-}
-
-/// Identifies a particular bound variable within a binder.
-/// Variables are identified by the combination of a [`DebruijnIndex`],
-/// which identifies the *binder*, and an index within that binder.
-///
-/// Consider this case:
-///
-/// ```ignore
-/// forall<'a, 'b> { forall<'c, 'd> { ... } }
-/// ```
-///
-/// Within the `...` term:
-///
-/// * the variable `'a` have a debruijn index of 1 and index 0
-/// * the variable `'b` have a debruijn index of 1 and index 1
-/// * the variable `'c` have a debruijn index of 0 and index 0
-/// * the variable `'d` have a debruijn index of 0 and index 1
-///
-/// The variables `'a` and `'b` both have debruijn index of 1 because,
-/// counting out, they are the 2nd binder enclosing `...`. The indices
-/// identify the location *within* that binder.
-///
-/// The variables `'c` and `'d` both have debruijn index of 0 because
-/// they appear in the *innermost* binder enclosing the `...`. The
-/// indices identify the location *within* that binder.
-#[derive(Copy, Clone, PartialEq, Eq, Hash, PartialOrd, Ord)]
-pub struct BoundVar {
-    /// Debruijn index, which identifies the binder.
-    pub debruijn: DebruijnIndex,
-    /// Index within the binder.
-    pub index: usize,
-}
-
-impl BoundVar {
-    /// Creates a new bound variable.
-    pub fn new(debruijn: DebruijnIndex, index: usize) -> Self {
-        Self { debruijn, index }
-    }
-
-    /// Casts the bound variable to a type.
-    pub fn to_ty<I: Interner>(self, interner: I) -> Ty<I> {
-        TyKind::<I>::BoundVar(self).intern(interner)
-    }
-
-    /// Wrap the bound variable in a lifetime.
-    pub fn to_lifetime<I: Interner>(self, interner: I) -> Lifetime<I> {
-        LifetimeData::<I>::BoundVar(self).intern(interner)
-    }
-
-    /// Wraps the bound variable in a constant.
-    pub fn to_const<I: Interner>(self, interner: I, ty: Ty<I>) -> Const<I> {
-        ConstData {
-            ty,
-            value: ConstValue::<I>::BoundVar(self),
-        }
-        .intern(interner)
-    }
-
-    /// True if this variable is bound within the `amount` innermost binders.
-    pub fn bound_within(self, outer_binder: DebruijnIndex) -> bool {
-        self.debruijn.within(outer_binder)
-    }
-
-    /// Adjusts the debruijn index (see [`DebruijnIndex::shifted_in`]).
-    #[must_use]
-    pub fn shifted_in(self) -> Self {
-        BoundVar::new(self.debruijn.shifted_in(), self.index)
-    }
-
-    /// Adjusts the debruijn index (see [`DebruijnIndex::shifted_in`]).
-    #[must_use]
-    pub fn shifted_in_from(self, outer_binder: DebruijnIndex) -> Self {
-        BoundVar::new(self.debruijn.shifted_in_from(outer_binder), self.index)
-    }
-
-    /// Adjusts the debruijn index (see [`DebruijnIndex::shifted_in`]).
-    #[must_use]
-    pub fn shifted_out(self) -> Option<Self> {
-        self.debruijn
-            .shifted_out()
-            .map(|db| BoundVar::new(db, self.index))
-    }
-
-    /// Adjusts the debruijn index (see [`DebruijnIndex::shifted_in`]).
-    #[must_use]
-    pub fn shifted_out_to(self, outer_binder: DebruijnIndex) -> Option<Self> {
-        self.debruijn
-            .shifted_out_to(outer_binder)
-            .map(|db| BoundVar::new(db, self.index))
-    }
-
-    /// Return the index of the bound variable, but only if it is bound
-    /// at the innermost binder. Otherwise, returns `None`.
-    pub fn index_if_innermost(self) -> Option<usize> {
-        self.index_if_bound_at(DebruijnIndex::INNERMOST)
-    }
-
-    /// Return the index of the bound variable, but only if it is bound
-    /// at the innermost binder. Otherwise, returns `None`.
-    pub fn index_if_bound_at(self, debruijn: DebruijnIndex) -> Option<usize> {
-        if self.debruijn == debruijn {
-            Some(self.index)
-        } else {
-            None
-        }
-    }
-}
-
-/// References the binder at the given depth. The index is a [de
-/// Bruijn index], so it counts back through the in-scope binders,
-/// with 0 being the innermost binder. This is used in impls and
-/// the like. For example, if we had a rule like `for<T> { (T:
-/// Clone) :- (T: Copy) }`, then `T` would be represented as a
-/// `BoundVar(0)` (as the `for` is the innermost binder).
-///
-/// [de Bruijn index]: https://en.wikipedia.org/wiki/De_Bruijn_index
-#[derive(Copy, Clone, PartialEq, Eq, Hash, PartialOrd, Ord)]
-pub struct DebruijnIndex {
-    depth: u32,
-}
-
-impl DebruijnIndex {
-    /// Innermost index.
-    pub const INNERMOST: DebruijnIndex = DebruijnIndex { depth: 0 };
-    /// One level higher than the innermost index.
-    pub const ONE: DebruijnIndex = DebruijnIndex { depth: 1 };
-
-    /// Creates a new de Bruijn index with a given depth.
-    pub fn new(depth: u32) -> Self {
-        DebruijnIndex { depth }
-    }
-
-    /// Depth of the De Bruijn index, counting from 0 starting with
-    /// the innermost binder.
-    pub fn depth(self) -> u32 {
-        self.depth
-    }
-
-    /// True if the binder identified by this index is within the
-    /// binder identified by the index `outer_binder`.
-    ///
-    /// # Example
-    ///
-    /// Imagine you have the following binders in scope
-    ///
-    /// ```ignore
-    /// forall<a> forall<b> forall<c>
-    /// ```
-    ///
-    /// then the Debruijn index for `c` would be `0`, the index for
-    /// `b` would be 1, and so on. Now consider the following calls:
-    ///
-    /// * `c.within(a) = true`
-    /// * `b.within(a) = true`
-    /// * `a.within(a) = false`
-    /// * `a.within(c) = false`
-    pub fn within(self, outer_binder: DebruijnIndex) -> bool {
-        self < outer_binder
-    }
-
-    /// Returns the resulting index when this value is moved into
-    /// through one binder.
-    #[must_use]
-    pub fn shifted_in(self) -> DebruijnIndex {
-        self.shifted_in_from(DebruijnIndex::ONE)
-    }
-
-    /// Update this index in place by shifting it "in" through
-    /// `amount` number of binders.
-    pub fn shift_in(&mut self) {
-        *self = self.shifted_in();
-    }
-
-    /// Adds `outer_binder` levels to the `self` index. Intuitively, this
-    /// shifts the `self` index, which was valid at the outer binder,
-    /// so that it is valid at the innermost binder.
-    ///
-    /// Example: Assume that the following binders are in scope:
-    ///
-    /// ```ignore
-    /// for<A> for<B> for<C> for<D>
-    ///            ^ outer binder
-    /// ```
-    ///
-    /// Assume further that the `outer_binder` argument is 2,
-    /// which means that it is referring to the `for<B>` binder
-    /// (since `D` would be the innermost binder).
-    ///
-    /// This means that `self` is relative to the binder `B` -- so
-    /// if `self` is 0 (`INNERMOST`), then it refers to `B`,
-    /// and if `self` is 1, then it refers to `A`.
-    ///
-    /// We will return as follows:
-    ///
-    /// * `0.shifted_in_from(2) = 2` -- i.e., `B`, when shifted in to the binding level `D`, has index 2
-    /// * `1.shifted_in_from(2) = 3` -- i.e., `A`, when shifted in to the binding level `D`, has index 3
-    /// * `2.shifted_in_from(1) = 3` -- here, we changed the `outer_binder`  to refer to `C`.
-    ///   Therefore `2` (relative to `C`) refers to `A`, so the result is still 3 (since `A`, relative to the
-    ///   innermost binder, has index 3).
-    #[must_use]
-    pub fn shifted_in_from(self, outer_binder: DebruijnIndex) -> DebruijnIndex {
-        DebruijnIndex::new(self.depth() + outer_binder.depth())
-    }
-
-    /// Returns the resulting index when this value is moved out from
-    /// `amount` number of new binders.
-    #[must_use]
-    pub fn shifted_out(self) -> Option<DebruijnIndex> {
-        self.shifted_out_to(DebruijnIndex::ONE)
-    }
-
-    /// Update in place by shifting out from `amount` binders.
-    pub fn shift_out(&mut self) {
-        *self = self.shifted_out().unwrap();
-    }
-
-    /// Subtracts `outer_binder` levels from the `self` index. Intuitively, this
-    /// shifts the `self` index, which was valid at the innermost
-    /// binder, to one that is valid at the binder `outer_binder`.
-    ///
-    /// This will return `None` if the `self` index is internal to the
-    /// outer binder (i.e., if `self < outer_binder`).
-    ///
-    /// Example: Assume that the following binders are in scope:
-    ///
-    /// ```ignore
-    /// for<A> for<B> for<C> for<D>
-    ///            ^ outer binder
-    /// ```
-    ///
-    /// Assume further that the `outer_binder` argument is 2,
-    /// which means that it is referring to the `for<B>` binder
-    /// (since `D` would be the innermost binder).
-    ///
-    /// This means that the result is relative to the binder `B` -- so
-    /// if `self` is 0 (`INNERMOST`), then it refers to `B`,
-    /// and if `self` is 1, then it refers to `A`.
-    ///
-    /// We will return as follows:
-    ///
-    /// * `1.shifted_out_to(2) = None` -- i.e., the binder for `C` can't be named from the binding level `B`
-    /// * `3.shifted_out_to(2) = Some(1)` -- i.e., `A`, when shifted out to the binding level `B`, has index 1
-    pub fn shifted_out_to(self, outer_binder: DebruijnIndex) -> Option<DebruijnIndex> {
-        if self.within(outer_binder) {
-            None
-        } else {
-            Some(DebruijnIndex::new(self.depth() - outer_binder.depth()))
-        }
-    }
-}
-
-/// A "DynTy" represents a trait object (`dyn Trait`). Trait objects
-/// are conceptually very related to an "existential type" of the form
-/// `exists<T> { T: Trait }` (another example of such type is `impl Trait`).
-/// `DynTy` represents the bounds on that type.
-///
-/// The "bounds" here represents the unknown self type. So, a type like
-/// `dyn for<'a> Fn(&'a u32)` would be represented with two-levels of
-/// binder, as "depicted" here:
-///
-/// ```notrust
-/// exists<type> {
-///    vec![
-///        // A QuantifiedWhereClause:
-///        forall<region> { ^1.0: Fn(&^0.0 u32) }
-///    ]
-/// }
-/// ```
-///
-/// The outer `exists<type>` binder indicates that there exists
-/// some type that meets the criteria within, but that type is not
-/// known. It is referenced within the type using `^1.0`, indicating
-/// a bound type with debruijn index 1 (i.e., skipping through one
-/// level of binder).
-#[derive(Clone, PartialEq, Eq, Hash, TypeFoldable, TypeVisitable, HasInterner)]
-pub struct DynTy<I: Interner> {
-    /// The unknown self type.
-    pub bounds: Binders<QuantifiedWhereClauses<I>>,
-    /// Lifetime of the `DynTy`.
-    pub lifetime: Lifetime<I>,
-}
-
-impl<I: Interner> Copy for DynTy<I>
-where
-    I::InternedLifetime: Copy,
-    I::InternedQuantifiedWhereClauses: Copy,
-    I::InternedVariableKinds: Copy,
-{
-}
-
-/// A type, lifetime or constant whose value is being inferred.
-#[derive(Copy, Clone, PartialEq, Eq, Hash, PartialOrd, Ord)]
-pub struct InferenceVar {
-    index: u32,
-}
-
-impl From<u32> for InferenceVar {
-    fn from(index: u32) -> InferenceVar {
-        InferenceVar { index }
-    }
-}
-
-impl InferenceVar {
-    /// Gets the underlying index value.
-    pub fn index(self) -> u32 {
-        self.index
-    }
-
-    /// Wraps the inference variable in a type.
-    pub fn to_ty<I: Interner>(self, interner: I, kind: TyVariableKind) -> Ty<I> {
-        TyKind::<I>::InferenceVar(self, kind).intern(interner)
-    }
-
-    /// Wraps the inference variable in a lifetime.
-    pub fn to_lifetime<I: Interner>(self, interner: I) -> Lifetime<I> {
-        LifetimeData::<I>::InferenceVar(self).intern(interner)
-    }
-
-    /// Wraps the inference variable in a constant.
-    pub fn to_const<I: Interner>(self, interner: I, ty: Ty<I>) -> Const<I> {
-        ConstData {
-            ty,
-            value: ConstValue::<I>::InferenceVar(self),
-        }
-        .intern(interner)
-    }
-}
-
-/// A function signature.
-#[derive(Clone, Copy, PartialEq, Eq, Hash, HasInterner, Debug)]
-#[allow(missing_docs)]
-pub struct FnSig<I: Interner> {
-    pub abi: I::FnAbi,
-    pub safety: Safety,
-    pub variadic: bool,
-}
-/// A wrapper for the substs on a Fn.
-#[derive(Clone, PartialEq, Eq, Hash, HasInterner, TypeFoldable, TypeVisitable)]
-pub struct FnSubst<I: Interner>(pub Substitution<I>);
-
-impl<I: Interner> Copy for FnSubst<I> where I::InternedSubstitution: Copy {}
-
-/// for<'a...'z> X -- all binders are instantiated at once,
-/// and we use deBruijn indices within `self.ty`
-#[derive(Clone, PartialEq, Eq, Hash, HasInterner)]
-#[allow(missing_docs)]
-pub struct FnPointer<I: Interner> {
-    pub num_binders: usize,
-    pub sig: FnSig<I>,
-    pub substitution: FnSubst<I>,
-}
-
-impl<I: Interner> Copy for FnPointer<I> where I::InternedSubstitution: Copy {}
-
-impl<I: Interner> FnPointer<I> {
-    /// Represent the current `Fn` as if it was wrapped in `Binders`
-    pub fn into_binders(self, interner: I) -> Binders<FnSubst<I>> {
-        Binders::new(
-            VariableKinds::from_iter(
-                interner,
-                (0..self.num_binders).map(|_| VariableKind::Lifetime),
-            ),
-            self.substitution,
-        )
-    }
-
-    /// Represent the current `Fn` as if it was wrapped in `Binders`
-    pub fn as_binders(&self, interner: I) -> Binders<&FnSubst<I>> {
-        Binders::new(
-            VariableKinds::from_iter(
-                interner,
-                (0..self.num_binders).map(|_| VariableKind::Lifetime),
-            ),
-            &self.substitution,
-        )
-    }
-}
-
-/// Constants.
-#[derive(Copy, Clone, PartialEq, Eq, Hash, PartialOrd, Ord, HasInterner)]
-pub struct Const<I: Interner> {
-    interned: I::InternedConst,
-}
-
-impl<I: Interner> Const<I> {
-    /// Create a `Const` using something that can be cast to const data.
-    pub fn new(interner: I, data: impl CastTo<ConstData<I>>) -> Self {
-        Const {
-            interned: I::intern_const(interner, data.cast(interner)),
-        }
-    }
-
-    /// Gets the interned constant.
-    pub fn interned(&self) -> &I::InternedConst {
-        &self.interned
-    }
-
-    /// Gets the constant data from the interner.
-    pub fn data(&self, interner: I) -> &ConstData<I> {
-        I::const_data(interner, &self.interned)
-    }
-
-    /// If this is a `ConstData::BoundVar(d)`, returns `Some(d)` else `None`.
-    pub fn bound_var(&self, interner: I) -> Option<BoundVar> {
-        if let ConstValue::BoundVar(bv) = &self.data(interner).value {
-            Some(*bv)
-        } else {
-            None
-        }
-    }
-
-    /// If this is a `ConstData::InferenceVar(d)`, returns `Some(d)` else `None`.
-    pub fn inference_var(&self, interner: I) -> Option<InferenceVar> {
-        if let ConstValue::InferenceVar(iv) = &self.data(interner).value {
-            Some(*iv)
-        } else {
-            None
-        }
-    }
-
-    /// True if this const is a "bound" const, and hence
-    /// needs to be shifted across binders. Meant for debug assertions.
-    pub fn needs_shift(&self, interner: I) -> bool {
-        match &self.data(interner).value {
-            ConstValue::BoundVar(_) => true,
-            ConstValue::InferenceVar(_) => false,
-            ConstValue::Placeholder(_) => false,
-            ConstValue::Concrete(_) => false,
-        }
-    }
-}
-
-/// Constant data, containing the constant's type and value.
-#[derive(Clone, PartialEq, Eq, Hash, HasInterner)]
-pub struct ConstData<I: Interner> {
-    /// Type that holds the constant.
-    pub ty: Ty<I>,
-    /// The value of the constant.
-    pub value: ConstValue<I>,
-}
-
-/// A constant value, not necessarily concrete.
-#[derive(Clone, PartialEq, Eq, Hash, HasInterner)]
-pub enum ConstValue<I: Interner> {
-    /// Bound var (e.g. a parameter).
-    BoundVar(BoundVar),
-    /// Constant whose value is being inferred.
-    InferenceVar(InferenceVar),
-    /// Lifetime on some yet-unknown placeholder.
-    Placeholder(PlaceholderIndex),
-    /// Concrete constant value.
-    Concrete(ConcreteConst<I>),
-}
-
-impl<I: Interner> Copy for ConstValue<I> where I::InternedConcreteConst: Copy {}
-
-impl<I: Interner> ConstData<I> {
-    /// Wraps the constant data in a `Const`.
-    pub fn intern(self, interner: I) -> Const<I> {
-        Const::new(interner, self)
-    }
-}
-
-/// Concrete constant, whose value is known (as opposed to
-/// inferred constants and placeholders).
-#[derive(Copy, Clone, PartialEq, Eq, Hash, PartialOrd, Ord, HasInterner)]
-pub struct ConcreteConst<I: Interner> {
-    /// The interned constant.
-    pub interned: I::InternedConcreteConst,
-}
-
-impl<I: Interner> ConcreteConst<I> {
-    /// Checks whether two concrete constants are equal.
-    pub fn const_eq(&self, ty: &Ty<I>, other: &ConcreteConst<I>, interner: I) -> bool {
-        interner.const_eq(&ty.interned, &self.interned, &other.interned)
-    }
-}
-
-/// A Rust lifetime.
-#[derive(Copy, Clone, PartialEq, Eq, Hash, PartialOrd, Ord, HasInterner)]
-pub struct Lifetime<I: Interner> {
-    interned: I::InternedLifetime,
-}
-
-impl<I: Interner> Lifetime<I> {
-    /// Create a lifetime from lifetime data
-    /// (or something that can be cast to lifetime data).
-    pub fn new(interner: I, data: impl CastTo<LifetimeData<I>>) -> Self {
-        Lifetime {
-            interned: I::intern_lifetime(interner, data.cast(interner)),
-        }
-    }
-
-    /// Gets the interned value.
-    pub fn interned(&self) -> &I::InternedLifetime {
-        &self.interned
-    }
-
-    /// Gets the lifetime data.
-    pub fn data(&self, interner: I) -> &LifetimeData<I> {
-        I::lifetime_data(interner, &self.interned)
-    }
-
-    /// If this is a `Lifetime::BoundVar(d)`, returns `Some(d)` else `None`.
-    pub fn bound_var(&self, interner: I) -> Option<BoundVar> {
-        if let LifetimeData::BoundVar(bv) = self.data(interner) {
-            Some(*bv)
-        } else {
-            None
-        }
-    }
-
-    /// If this is a `Lifetime::InferenceVar(d)`, returns `Some(d)` else `None`.
-    pub fn inference_var(&self, interner: I) -> Option<InferenceVar> {
-        if let LifetimeData::InferenceVar(depth) = self.data(interner) {
-            Some(*depth)
-        } else {
-            None
-        }
-    }
-
-    /// True if this lifetime is a "bound" lifetime, and hence
-    /// needs to be shifted across binders. Meant for debug assertions.
-    pub fn needs_shift(&self, interner: I) -> bool {
-        match self.data(interner) {
-            LifetimeData::BoundVar(_) => true,
-            LifetimeData::InferenceVar(_) => false,
-            LifetimeData::Placeholder(_) => false,
-            LifetimeData::Static => false,
-            LifetimeData::Erased => false,
-            LifetimeData::Phantom(..) => unreachable!(),
-        }
-    }
-
-    ///compute type flags for Lifetime
-    fn compute_flags(&self, interner: I) -> TypeFlags {
-        match self.data(interner) {
-            LifetimeData::InferenceVar(_) => {
-                TypeFlags::HAS_RE_INFER
-                    | TypeFlags::HAS_FREE_LOCAL_REGIONS
-                    | TypeFlags::HAS_FREE_REGIONS
-            }
-            LifetimeData::Placeholder(_) => {
-                TypeFlags::HAS_RE_PLACEHOLDER
-                    | TypeFlags::HAS_FREE_LOCAL_REGIONS
-                    | TypeFlags::HAS_FREE_REGIONS
-            }
-            LifetimeData::Static => TypeFlags::HAS_FREE_REGIONS,
-            LifetimeData::Phantom(_, _) => TypeFlags::empty(),
-            LifetimeData::BoundVar(_) => TypeFlags::HAS_RE_LATE_BOUND,
-            LifetimeData::Erased => TypeFlags::HAS_RE_ERASED,
-        }
-    }
-}
-
-/// Lifetime data, including what kind of lifetime it is and what it points to.
-#[derive(Copy, Clone, PartialEq, Eq, Hash, PartialOrd, Ord, HasInterner)]
-pub enum LifetimeData<I: Interner> {
-    /// See TyKind::BoundVar.
-    BoundVar(BoundVar),
-    /// Lifetime whose value is being inferred.
-    InferenceVar(InferenceVar),
-    /// Lifetime on some yet-unknown placeholder.
-    Placeholder(PlaceholderIndex),
-    /// Static lifetime
-    Static,
-    /// An erased lifetime, used by rustc to improve caching when we doesn't
-    /// care about lifetimes
-    Erased,
-    /// Lifetime on phantom data.
-    Phantom(Void, PhantomData<I>),
-}
-
-impl<I: Interner> LifetimeData<I> {
-    /// Wrap the lifetime data in a lifetime.
-    pub fn intern(self, interner: I) -> Lifetime<I> {
-        Lifetime::new(interner, self)
-    }
-}
-
-/// Index of an universally quantified parameter in the environment.
-/// Two indexes are required, the one of the universe itself
-/// and the relative index inside the universe.
-#[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash)]
-pub struct PlaceholderIndex {
-    /// Index *of* the universe.
-    pub ui: UniverseIndex,
-    /// Index *in* the universe.
-    pub idx: usize,
-}
-
-impl PlaceholderIndex {
-    /// Wrap the placeholder instance in a lifetime.
-    pub fn to_lifetime<I: Interner>(self, interner: I) -> Lifetime<I> {
-        LifetimeData::<I>::Placeholder(self).intern(interner)
-    }
-
-    /// Create an interned type.
-    pub fn to_ty<I: Interner>(self, interner: I) -> Ty<I> {
-        TyKind::Placeholder(self).intern(interner)
-    }
-
-    /// Wrap the placeholder index in a constant.
-    pub fn to_const<I: Interner>(self, interner: I, ty: Ty<I>) -> Const<I> {
-        ConstData {
-            ty,
-            value: ConstValue::Placeholder(self),
-        }
-        .intern(interner)
-    }
-}
-/// Represents some extra knowledge we may have about the type variable.
-/// ```ignore
-/// let x: &[u32];
-/// let i = 1;
-/// x[i]
-/// ```
-/// In this example, `i` is known to be some type of integer. We can infer that
-/// it is `usize` because that is the only integer type that slices have an
-/// `Index` impl for. `i` would have a `TyVariableKind` of `Integer` to guide the
-/// inference process.
-#[derive(Copy, Clone, Debug, PartialEq, Eq, Hash)]
-#[allow(missing_docs)]
-pub enum TyVariableKind {
-    General,
-    Integer,
-    Float,
-}
-
-/// The "kind" of variable. Type, lifetime or constant.
-#[derive(Clone, PartialEq, Eq, Hash)]
-#[allow(missing_docs)]
-pub enum VariableKind<I: Interner> {
-    Ty(TyVariableKind),
-    Lifetime,
-    Const(Ty<I>),
-}
-
-impl<I: Interner> interner::HasInterner for VariableKind<I> {
-    type Interner = I;
-}
-
-impl<I: Interner> Copy for VariableKind<I> where I::InternedType: Copy {}
-
-impl<I: Interner> VariableKind<I> {
-    fn to_bound_variable(&self, interner: I, bound_var: BoundVar) -> GenericArg<I> {
-        match self {
-            VariableKind::Ty(_) => {
-                GenericArgData::Ty(TyKind::BoundVar(bound_var).intern(interner)).intern(interner)
-            }
-            VariableKind::Lifetime => {
-                GenericArgData::Lifetime(LifetimeData::BoundVar(bound_var).intern(interner))
-                    .intern(interner)
-            }
-            VariableKind::Const(ty) => GenericArgData::Const(
-                ConstData {
-                    ty: ty.clone(),
-                    value: ConstValue::BoundVar(bound_var),
-                }
-                .intern(interner),
-            )
-            .intern(interner),
-        }
-    }
-}
-
-/// A generic argument, see `GenericArgData` for more information.
-#[derive(Copy, Clone, PartialEq, Eq, Hash, PartialOrd, Ord, HasInterner)]
-pub struct GenericArg<I: Interner> {
-    interned: I::InternedGenericArg,
-}
-
-impl<I: Interner> GenericArg<I> {
-    /// Constructs a generic argument using `GenericArgData`.
-    pub fn new(interner: I, data: GenericArgData<I>) -> Self {
-        let interned = I::intern_generic_arg(interner, data);
-        GenericArg { interned }
-    }
-
-    /// Gets the interned value.
-    pub fn interned(&self) -> &I::InternedGenericArg {
-        &self.interned
-    }
-
-    /// Gets the underlying data.
-    pub fn data(&self, interner: I) -> &GenericArgData<I> {
-        I::generic_arg_data(interner, &self.interned)
-    }
-
-    /// Asserts that this is a type argument.
-    pub fn assert_ty_ref(&self, interner: I) -> &Ty<I> {
-        self.ty(interner).unwrap()
-    }
-
-    /// Asserts that this is a lifetime argument.
-    pub fn assert_lifetime_ref(&self, interner: I) -> &Lifetime<I> {
-        self.lifetime(interner).unwrap()
-    }
-
-    /// Asserts that this is a constant argument.
-    pub fn assert_const_ref(&self, interner: I) -> &Const<I> {
-        self.constant(interner).unwrap()
-    }
-
-    /// Checks whether the generic argument is a type.
-    pub fn is_ty(&self, interner: I) -> bool {
-        match self.data(interner) {
-            GenericArgData::Ty(_) => true,
-            GenericArgData::Lifetime(_) => false,
-            GenericArgData::Const(_) => false,
-        }
-    }
-
-    /// Returns the type if it is one, `None` otherwise.
-    pub fn ty(&self, interner: I) -> Option<&Ty<I>> {
-        match self.data(interner) {
-            GenericArgData::Ty(t) => Some(t),
-            _ => None,
-        }
-    }
-
-    /// Returns the lifetime if it is one, `None` otherwise.
-    pub fn lifetime(&self, interner: I) -> Option<&Lifetime<I>> {
-        match self.data(interner) {
-            GenericArgData::Lifetime(t) => Some(t),
-            _ => None,
-        }
-    }
-
-    /// Returns the constant if it is one, `None` otherwise.
-    pub fn constant(&self, interner: I) -> Option<&Const<I>> {
-        match self.data(interner) {
-            GenericArgData::Const(c) => Some(c),
-            _ => None,
-        }
-    }
-
-    /// Compute type flags for GenericArg<I>
-    fn compute_flags(&self, interner: I) -> TypeFlags {
-        match self.data(interner) {
-            GenericArgData::Ty(ty) => ty.data(interner).flags,
-            GenericArgData::Lifetime(lifetime) => lifetime.compute_flags(interner),
-            GenericArgData::Const(constant) => {
-                let data = constant.data(interner);
-                let flags = data.ty.data(interner).flags;
-                match data.value {
-                    ConstValue::BoundVar(_) => flags,
-                    ConstValue::InferenceVar(_) => {
-                        flags | TypeFlags::HAS_CT_INFER | TypeFlags::STILL_FURTHER_SPECIALIZABLE
-                    }
-                    ConstValue::Placeholder(_) => {
-                        flags
-                            | TypeFlags::HAS_CT_PLACEHOLDER
-                            | TypeFlags::STILL_FURTHER_SPECIALIZABLE
-                    }
-                    ConstValue::Concrete(_) => flags,
-                }
-            }
-        }
-    }
-}
-
-/// Generic arguments data.
-#[derive(Clone, PartialEq, Eq, Hash, TypeVisitable, TypeFoldable, Zip)]
-pub enum GenericArgData<I: Interner> {
-    /// Type argument
-    Ty(Ty<I>),
-    /// Lifetime argument
-    Lifetime(Lifetime<I>),
-    /// Constant argument
-    Const(Const<I>),
-}
-
-impl<I: Interner> Copy for GenericArgData<I>
-where
-    I::InternedType: Copy,
-    I::InternedLifetime: Copy,
-    I::InternedConst: Copy,
-{
-}
-
-impl<I: Interner> GenericArgData<I> {
-    /// Create an interned type.
-    pub fn intern(self, interner: I) -> GenericArg<I> {
-        GenericArg::new(interner, self)
-    }
-}
-
-/// A value with an associated variable kind.
-#[derive(Clone, PartialEq, Eq, Hash)]
-pub struct WithKind<I: Interner, T> {
-    /// The associated variable kind.
-    pub kind: VariableKind<I>,
-    /// The wrapped value.
-    value: T,
-}
-
-impl<I: Interner, T: Copy> Copy for WithKind<I, T> where I::InternedType: Copy {}
-
-impl<I: Interner, T> HasInterner for WithKind<I, T> {
-    type Interner = I;
-}
-
-impl<I: Interner, T> From<WithKind<I, T>> for (VariableKind<I>, T) {
-    fn from(with_kind: WithKind<I, T>) -> Self {
-        (with_kind.kind, with_kind.value)
-    }
-}
-
-impl<I: Interner, T> WithKind<I, T> {
-    /// Creates a `WithKind` from a variable kind and a value.
-    pub fn new(kind: VariableKind<I>, value: T) -> Self {
-        Self { kind, value }
-    }
-
-    /// Maps the value in `WithKind`.
-    pub fn map<U, OP>(self, op: OP) -> WithKind<I, U>
-    where
-        OP: FnOnce(T) -> U,
-    {
-        WithKind {
-            kind: self.kind,
-            value: op(self.value),
-        }
-    }
-
-    /// Maps a function taking `WithKind<I, &T>` over `&WithKind<I, T>`.
-    pub fn map_ref<U, OP>(&self, op: OP) -> WithKind<I, U>
-    where
-        OP: FnOnce(&T) -> U,
-    {
-        WithKind {
-            kind: self.kind.clone(),
-            value: op(&self.value),
-        }
-    }
-
-    /// Extract the value, ignoring the variable kind.
-    pub fn skip_kind(&self) -> &T {
-        &self.value
-    }
-}
-
-/// A variable kind with universe index.
-#[allow(type_alias_bounds)]
-pub type CanonicalVarKind<I: Interner> = WithKind<I, UniverseIndex>;
-
-/// An alias, which is a trait indirection such as a projection or opaque type.
-#[derive(Clone, PartialEq, Eq, Hash, TypeFoldable, TypeVisitable, HasInterner, Zip)]
-pub enum AliasTy<I: Interner> {
-    /// An associated type projection.
-    Projection(ProjectionTy<I>),
-    /// An opaque type.
-    Opaque(OpaqueTy<I>),
-}
-
-impl<I: Interner> Copy for AliasTy<I> where I::InternedSubstitution: Copy {}
-
-impl<I: Interner> AliasTy<I> {
-    /// Create an interned type for this alias.
-    pub fn intern(self, interner: I) -> Ty<I> {
-        Ty::new(interner, self)
-    }
-
-    /// Compute type flags for aliases
-    fn compute_flags(&self, interner: I) -> TypeFlags {
-        match self {
-            AliasTy::Projection(projection_ty) => {
-                TypeFlags::HAS_TY_PROJECTION | projection_ty.substitution.compute_flags(interner)
-            }
-            AliasTy::Opaque(opaque_ty) => {
-                TypeFlags::HAS_TY_OPAQUE | opaque_ty.substitution.compute_flags(interner)
-            }
-        }
-    }
-}
-
-/// A projection `<P0 as TraitName<P1..Pn>>::AssocItem<Pn+1..Pm>`.
-#[derive(Clone, PartialEq, Eq, Hash, TypeFoldable, TypeVisitable, HasInterner)]
-pub struct ProjectionTy<I: Interner> {
-    /// The id for the associated type member.
-    pub associated_ty_id: AssocTypeId<I>,
-    /// The substitution for the projection.
-    pub substitution: Substitution<I>,
-}
-
-impl<I: Interner> Copy for ProjectionTy<I> where I::InternedSubstitution: Copy {}
-
-/// An opaque type `opaque type T<..>: Trait = HiddenTy`.
-#[derive(Clone, PartialEq, Eq, Hash, TypeFoldable, TypeVisitable, HasInterner)]
-pub struct OpaqueTy<I: Interner> {
-    /// The id for the opaque type.
-    pub opaque_ty_id: OpaqueTyId<I>,
-    /// The substitution for the opaque type.
-    pub substitution: Substitution<I>,
-}
-
-impl<I: Interner> Copy for OpaqueTy<I> where I::InternedSubstitution: Copy {}
-
-/// A trait reference describes the relationship between a type and a trait.
-/// This can be used in two forms:
-/// - `P0: Trait<P1..Pn>` (e.g. `i32: Copy`), which mentions that the type
-///   implements the trait.
-/// - `<P0 as Trait<P1..Pn>>` (e.g. `i32 as Copy`), which casts the type to
-///   that specific trait.
-#[derive(Clone, PartialEq, Eq, Hash, TypeFoldable, TypeVisitable, HasInterner)]
-pub struct TraitRef<I: Interner> {
-    /// The trait id.
-    pub trait_id: TraitId<I>,
-    /// The substitution, containing both the `Self` type and the parameters.
-    pub substitution: Substitution<I>,
-}
-
-impl<I: Interner> Copy for TraitRef<I> where I::InternedSubstitution: Copy {}
-
-impl<I: Interner> TraitRef<I> {
-    /// Gets all type parameters in this trait ref, including `Self`.
-    pub fn type_parameters(&self, interner: I) -> impl Iterator<Item = Ty<I>> + '_ {
-        self.substitution
-            .iter(interner)
-            .filter_map(move |p| p.ty(interner))
-            .cloned()
-    }
-
-    /// Gets the type parameters of the `Self` type in this trait ref.
-    pub fn self_type_parameter(&self, interner: I) -> Ty<I> {
-        self.type_parameters(interner).next().unwrap()
-    }
-
-    /// Construct a `FromEnv` using this trait ref.
-    pub fn from_env(self) -> FromEnv<I> {
-        FromEnv::Trait(self)
-    }
-
-    /// Construct a `WellFormed` using this trait ref.
-    pub fn well_formed(self) -> WellFormed<I> {
-        WellFormed::Trait(self)
-    }
-}
-
-/// Lifetime outlives, which for `'a: 'b`` checks that the lifetime `'a`
-/// is a superset of the value of `'b`.
-#[derive(Clone, PartialEq, Eq, Hash, TypeFoldable, TypeVisitable, HasInterner, Zip)]
-#[allow(missing_docs)]
-pub struct LifetimeOutlives<I: Interner> {
-    pub a: Lifetime<I>,
-    pub b: Lifetime<I>,
-}
-
-impl<I: Interner> Copy for LifetimeOutlives<I> where I::InternedLifetime: Copy {}
-
-/// Type outlives, which for `T: 'a` checks that the type `T`
-/// lives at least as long as the lifetime `'a`
-#[derive(Clone, PartialEq, Eq, Hash, TypeFoldable, TypeVisitable, HasInterner, Zip)]
-pub struct TypeOutlives<I: Interner> {
-    /// The type which must outlive the given lifetime.
-    pub ty: Ty<I>,
-    /// The lifetime which the type must outlive.
-    pub lifetime: Lifetime<I>,
-}
-
-impl<I: Interner> Copy for TypeOutlives<I>
-where
-    I::InternedLifetime: Copy,
-    I::InternedType: Copy,
-{
-}
-
-/// Where clauses that can be written by a Rust programmer.
-#[derive(Clone, PartialEq, Eq, Hash, TypeFoldable, TypeSuperVisitable, HasInterner, Zip)]
-pub enum WhereClause<I: Interner> {
-    /// Type implements a trait.
-    Implemented(TraitRef<I>),
-    /// Type is equal to an alias.
-    AliasEq(AliasEq<I>),
-    /// One lifetime outlives another.
-    LifetimeOutlives(LifetimeOutlives<I>),
-    /// Type outlives a lifetime.
-    TypeOutlives(TypeOutlives<I>),
-}
-
-impl<I: Interner> Copy for WhereClause<I>
-where
-    I::InternedSubstitution: Copy,
-    I::InternedLifetime: Copy,
-    I::InternedType: Copy,
-{
-}
-
-/// Checks whether a type or trait ref is well-formed.
-#[derive(Clone, PartialEq, Eq, Hash, TypeFoldable, TypeVisitable, HasInterner, Zip)]
-pub enum WellFormed<I: Interner> {
-    /// A predicate which is true when some trait ref is well-formed.
-    /// For example, given the following trait definitions:
-    ///
-    /// ```notrust
-    /// trait Clone { ... }
-    /// trait Copy where Self: Clone { ... }
-    /// ```
-    ///
-    /// then we have the following rule:
-    ///
-    /// ```notrust
-    /// WellFormed(?Self: Copy) :- ?Self: Copy, WellFormed(?Self: Clone)
-    /// ```
-    Trait(TraitRef<I>),
-
-    /// A predicate which is true when some type is well-formed.
-    /// For example, given the following type definition:
-    ///
-    /// ```notrust
-    /// struct Set<K> where K: Hash {
-    ///     ...
-    /// }
-    /// ```
-    ///
-    /// then we have the following rule: `WellFormedTy(Set<K>) :- Implemented(K: Hash)`.
-    Ty(Ty<I>),
-}
-
-impl<I: Interner> Copy for WellFormed<I>
-where
-    I::InternedType: Copy,
-    I::InternedSubstitution: Copy,
-{
-}
-
-/// Checks whether a type or trait ref can be derived from the contents of the environment.
-#[derive(Clone, PartialEq, Eq, Hash, TypeFoldable, TypeVisitable, HasInterner, Zip)]
-pub enum FromEnv<I: Interner> {
-    /// A predicate which enables deriving everything which should be true if we *know* that
-    /// some trait ref is well-formed. For example given the above trait definitions, we can use
-    /// `FromEnv(T: Copy)` to derive that `T: Clone`, like in:
-    ///
-    /// ```notrust
-    /// forall<T> {
-    ///     if (FromEnv(T: Copy)) {
-    ///         T: Clone
-    ///     }
-    /// }
-    /// ```
-    Trait(TraitRef<I>),
-
-    /// A predicate which enables deriving everything which should be true if we *know* that
-    /// some type is well-formed. For example given the above type definition, we can use
-    /// `FromEnv(Set<K>)` to derive that `K: Hash`, like in:
-    ///
-    /// ```notrust
-    /// forall<K> {
-    ///     if (FromEnv(Set<K>)) {
-    ///         K: Hash
-    ///     }
-    /// }
-    /// ```
-    Ty(Ty<I>),
-}
-
-impl<I: Interner> Copy for FromEnv<I>
-where
-    I::InternedType: Copy,
-    I::InternedSubstitution: Copy,
-{
-}
-
-/// A "domain goal" is a goal that is directly about Rust, rather than a pure
-/// logical statement. As much as possible, the Chalk solver should avoid
-/// decomposing this enum, and instead treat its values opaquely.
-#[derive(Clone, PartialEq, Eq, Hash, TypeFoldable, TypeSuperVisitable, HasInterner, Zip)]
-pub enum DomainGoal<I: Interner> {
-    /// Simple goal that is true if the where clause is true.
-    Holds(WhereClause<I>),
-
-    /// True if the type or trait ref is well-formed.
-    WellFormed(WellFormed<I>),
-
-    /// True if the trait ref can be derived from in-scope where clauses.
-    FromEnv(FromEnv<I>),
-
-    /// True if the alias type can be normalized to some other type
-    Normalize(Normalize<I>),
-
-    /// True if a type is considered to have been "defined" by the current crate. This is true for
-    /// a `struct Foo { }` but false for a `#[upstream] struct Foo { }`. However, for fundamental types
-    /// like `Box<T>`, it is true if `T` is local.
-    IsLocal(Ty<I>),
-
-    /// True if a type is *not* considered to have been "defined" by the current crate. This is
-    /// false for a `struct Foo { }` but true for a `#[upstream] struct Foo { }`. However, for
-    /// fundamental types like `Box<T>`, it is true if `T` is upstream.
-    IsUpstream(Ty<I>),
-
-    /// True if a type and its input types are fully visible, known types. That is, there are no
-    /// unknown type parameters anywhere in this type.
-    ///
-    /// More formally, for each struct S<P0..Pn>:
-    /// forall<P0..Pn> {
-    ///     IsFullyVisible(S<P0...Pn>) :-
-    ///         IsFullyVisible(P0),
-    ///         ...
-    ///         IsFullyVisible(Pn)
-    /// }
-    ///
-    /// Note that any of these types can have lifetimes in their parameters too, but we only
-    /// consider type parameters.
-    IsFullyVisible(Ty<I>),
-
-    /// Used to dictate when trait impls are allowed in the current (local) crate based on the
-    /// orphan rules.
-    ///
-    /// `LocalImplAllowed(T: Trait)` is true if the type T is allowed to impl trait Trait in
-    /// the current crate. Under the current rules, this is unconditionally true for all types if
-    /// the Trait is considered to be "defined" in the current crate. If that is not the case, then
-    /// `LocalImplAllowed(T: Trait)` can still be true if `IsLocal(T)` is true.
-    LocalImplAllowed(TraitRef<I>),
-
-    /// Used to activate the "compatible modality" rules. Rules that introduce predicates that have
-    /// to do with "all compatible universes" should depend on this clause so that they only apply
-    /// if this is present.
-    Compatible,
-
-    /// Used to indicate that a given type is in a downstream crate. Downstream crates contain the
-    /// current crate at some level of their dependencies.
-    ///
-    /// Since chalk does not actually see downstream types, this is usually introduced with
-    /// implication on a fresh, universally quantified type.
-    ///
-    /// forall<T> { if (DownstreamType(T)) { /* ... */ } }
-    ///
-    /// This makes a new type `T` available and makes `DownstreamType(T)` provable for that type.
-    DownstreamType(Ty<I>),
-
-    /// Used to activate the "reveal mode", in which opaque (`impl Trait`) types can be equated
-    /// to their actual type.
-    Reveal,
-
-    /// Used to indicate that a trait is object safe.
-    ObjectSafe(TraitId<I>),
-}
-
-impl<I: Interner> Copy for DomainGoal<I>
-where
-    I::InternedSubstitution: Copy,
-    I::InternedLifetime: Copy,
-    I::InternedType: Copy,
-{
-}
-
-/// A where clause that can contain `forall<>` or `exists<>` quantifiers.
-pub type QuantifiedWhereClause<I> = Binders<WhereClause<I>>;
-
-impl<I: Interner> WhereClause<I> {
-    /// Turn a where clause into the WF version of it i.e.:
-    /// * `Implemented(T: Trait)` maps to `WellFormed(T: Trait)`
-    /// * `ProjectionEq(<T as Trait>::Item = Foo)` maps to `WellFormed(<T as Trait>::Item = Foo)`
-    /// * any other clause maps to itself
-    pub fn into_well_formed_goal(self, interner: I) -> DomainGoal<I> {
-        match self {
-            WhereClause::Implemented(trait_ref) => WellFormed::Trait(trait_ref).cast(interner),
-            wc => wc.cast(interner),
-        }
-    }
-
-    /// Same as `into_well_formed_goal` but with the `FromEnv` predicate instead of `WellFormed`.
-    pub fn into_from_env_goal(self, interner: I) -> DomainGoal<I> {
-        match self {
-            WhereClause::Implemented(trait_ref) => FromEnv::Trait(trait_ref).cast(interner),
-            wc => wc.cast(interner),
-        }
-    }
-
-    /// If where clause is a `TraitRef`, returns its trait id.
-    pub fn trait_id(&self) -> Option<TraitId<I>> {
-        match self {
-            WhereClause::Implemented(trait_ref) => Some(trait_ref.trait_id),
-            WhereClause::AliasEq(_) => None,
-            WhereClause::LifetimeOutlives(_) => None,
-            WhereClause::TypeOutlives(_) => None,
-        }
-    }
-}
-
-impl<I: Interner> QuantifiedWhereClause<I> {
-    /// As with `WhereClause::into_well_formed_goal`, but for a
-    /// quantified where clause. For example, `forall<T> {
-    /// Implemented(T: Trait)}` would map to `forall<T> {
-    /// WellFormed(T: Trait) }`.
-    pub fn into_well_formed_goal(self, interner: I) -> Binders<DomainGoal<I>> {
-        self.map(|wc| wc.into_well_formed_goal(interner))
-    }
-
-    /// As with `WhereClause::into_from_env_goal`, but mapped over any
-    /// binders. For example, `forall<T> {
-    /// Implemented(T: Trait)}` would map to `forall<T> {
-    /// FromEnv(T: Trait) }`.
-    pub fn into_from_env_goal(self, interner: I) -> Binders<DomainGoal<I>> {
-        self.map(|wc| wc.into_from_env_goal(interner))
-    }
-
-    /// If the underlying where clause is a `TraitRef`, returns its trait id.
-    pub fn trait_id(&self) -> Option<TraitId<I>> {
-        self.skip_binders().trait_id()
-    }
-}
-
-impl<I: Interner> DomainGoal<I> {
-    /// Convert `Implemented(...)` into `FromEnv(...)`, but leave other
-    /// goals unchanged.
-    pub fn into_from_env_goal(self, interner: I) -> DomainGoal<I> {
-        match self {
-            DomainGoal::Holds(wc) => wc.into_from_env_goal(interner),
-            goal => goal,
-        }
-    }
-
-    /// Lists generic arguments that are inputs to this domain goal.
-    pub fn inputs(&self, interner: I) -> Vec<GenericArg<I>> {
-        match self {
-            DomainGoal::Holds(WhereClause::AliasEq(alias_eq)) => {
-                vec![GenericArgData::Ty(alias_eq.alias.clone().intern(interner)).intern(interner)]
-            }
-            _ => Vec::new(),
-        }
-    }
-}
-
-/// Equality goal: tries to prove that two values are equal.
-#[derive(Clone, PartialEq, Eq, Hash, TypeFoldable, TypeVisitable, Zip)]
-#[allow(missing_docs)]
-pub struct EqGoal<I: Interner> {
-    pub a: GenericArg<I>,
-    pub b: GenericArg<I>,
-}
-
-impl<I: Interner> Copy for EqGoal<I> where I::InternedGenericArg: Copy {}
-
-/// Subtype goal: tries to prove that `a` is a subtype of `b`
-#[derive(Clone, PartialEq, Eq, Hash, TypeFoldable, TypeVisitable, Zip)]
-#[allow(missing_docs)]
-pub struct SubtypeGoal<I: Interner> {
-    pub a: Ty<I>,
-    pub b: Ty<I>,
-}
-
-impl<I: Interner> Copy for SubtypeGoal<I> where I::InternedType: Copy {}
-
-/// Proves that the given type alias **normalizes** to the given
-/// type. A projection `T::Foo` normalizes to the type `U` if we can
-/// **match it to an impl** and that impl has a `type Foo = V` where
-/// `U = V`.
-#[derive(Clone, PartialEq, Eq, Hash, TypeFoldable, TypeVisitable, Zip)]
-#[allow(missing_docs)]
-pub struct Normalize<I: Interner> {
-    pub alias: AliasTy<I>,
-    pub ty: Ty<I>,
-}
-
-impl<I: Interner> Copy for Normalize<I>
-where
-    I::InternedSubstitution: Copy,
-    I::InternedType: Copy,
-{
-}
-
-/// Proves **equality** between an alias and a type.
-#[derive(Clone, PartialEq, Eq, Hash, TypeFoldable, TypeVisitable, Zip)]
-#[allow(missing_docs)]
-pub struct AliasEq<I: Interner> {
-    pub alias: AliasTy<I>,
-    pub ty: Ty<I>,
-}
-
-impl<I: Interner> Copy for AliasEq<I>
-where
-    I::InternedSubstitution: Copy,
-    I::InternedType: Copy,
-{
-}
-
-impl<I: Interner> HasInterner for AliasEq<I> {
-    type Interner = I;
-}
-
-/// Indicates that the `value` is universally quantified over `N`
-/// parameters of the given kinds, where `N == self.binders.len()`. A
-/// variable with depth `i < N` refers to the value at
-/// `self.binders[i]`. Variables with depth `>= N` are free.
-///
-/// (IOW, we use deBruijn indices, where binders are introduced in reverse order
-/// of `self.binders`.)
-#[derive(Clone, PartialEq, Eq, Hash)]
-pub struct Binders<T: HasInterner> {
-    /// The binders that quantify over the value.
-    pub binders: VariableKinds<T::Interner>,
-
-    /// The value being quantified over.
-    value: T,
-}
-
-impl<T: HasInterner + Copy> Copy for Binders<T> where
-    <T::Interner as Interner>::InternedVariableKinds: Copy
-{
-}
-
-impl<T: HasInterner> HasInterner for Binders<T> {
-    type Interner = T::Interner;
-}
-
-impl<T: Clone + HasInterner> Binders<&T> {
-    /// Converts a `Binders<&T>` to a `Binders<T>` by cloning `T`.
-    pub fn cloned(self) -> Binders<T> {
-        self.map(Clone::clone)
-    }
-}
-
-impl<T: HasInterner> Binders<T> {
-    /// Create new binders.
-    pub fn new(binders: VariableKinds<T::Interner>, value: T) -> Self {
-        Self { binders, value }
-    }
-
-    /// Wraps the given value in a binder without variables, i.e. `for<>
-    /// (value)`. Since our deBruijn indices count binders, not variables, this
-    /// is sometimes useful.
-    pub fn empty(interner: T::Interner, value: T) -> Self {
-        let binders = VariableKinds::empty(interner);
-        Self { binders, value }
-    }
-
-    /// Skips the binder and returns the "bound" value. This is a
-    /// risky thing to do because it's easy to get confused about
-    /// De Bruijn indices and the like. `skip_binder` is only valid
-    /// when you are either extracting data that has nothing to
-    /// do with bound vars, or you are being very careful about
-    /// your depth accounting.
-    ///
-    /// Some examples where `skip_binder` is reasonable:
-    ///
-    /// - extracting the `TraitId` from a TraitRef;
-    /// - checking if there are any fields in a StructDatum
-    pub fn skip_binders(&self) -> &T {
-        &self.value
-    }
-
-    /// Skips the binder and returns the "bound" value as well as the skipped free variables. This
-    /// is just as risky as [`skip_binders`][Self::skip_binders].
-    pub fn into_value_and_skipped_binders(self) -> (T, VariableKinds<T::Interner>) {
-        (self.value, self.binders)
-    }
-
-    /// Converts `&Binders<T>` to `Binders<&T>`. Produces new `Binders`
-    /// with cloned quantifiers containing a reference to the original
-    /// value, leaving the original in place.
-    pub fn as_ref(&self) -> Binders<&T> {
-        Binders {
-            binders: self.binders.clone(),
-            value: &self.value,
-        }
-    }
-
-    /// Maps the binders by applying a function.
-    pub fn map<U, OP>(self, op: OP) -> Binders<U>
-    where
-        OP: FnOnce(T) -> U,
-        U: HasInterner<Interner = T::Interner>,
-    {
-        let value = op(self.value);
-        Binders {
-            binders: self.binders,
-            value,
-        }
-    }
-
-    /// Transforms the inner value according to the given function; returns
-    /// `None` if the function returns `None`.
-    pub fn filter_map<U, OP>(self, op: OP) -> Option<Binders<U>>
-    where
-        OP: FnOnce(T) -> Option<U>,
-        U: HasInterner<Interner = T::Interner>,
-    {
-        let value = op(self.value)?;
-        Some(Binders {
-            binders: self.binders,
-            value,
-        })
-    }
-
-    /// Maps a function taking `Binders<&T>` over `&Binders<T>`.
-    pub fn map_ref<'a, U, OP>(&'a self, op: OP) -> Binders<U>
-    where
-        OP: FnOnce(&'a T) -> U,
-        U: HasInterner<Interner = T::Interner>,
-    {
-        self.as_ref().map(op)
-    }
-
-    /// Creates a `Substitution` containing bound vars such that applying this
-    /// substitution will not change the value, i.e. `^0.0, ^0.1, ^0.2` and so
-    /// on.
-    pub fn identity_substitution(&self, interner: T::Interner) -> Substitution<T::Interner> {
-        Substitution::from_iter(
-            interner,
-            self.binders
-                .iter(interner)
-                .enumerate()
-                .map(|p| p.to_generic_arg(interner)),
-        )
-    }
-
-    /// Creates a fresh binders that contains a single type
-    /// variable. The result of the closure will be embedded in this
-    /// binder. Note that you should be careful with what you return
-    /// from the closure to account for the binder that will be added.
-    ///
-    /// XXX FIXME -- this is potentially a pretty footgun-y function.
-    pub fn with_fresh_type_var(
-        interner: T::Interner,
-        op: impl FnOnce(Ty<T::Interner>) -> T,
-    ) -> Binders<T> {
-        // The new variable is at the front and everything afterwards is shifted up by 1
-        let new_var = TyKind::BoundVar(BoundVar::new(DebruijnIndex::INNERMOST, 0)).intern(interner);
-        let value = op(new_var);
-        let binders = VariableKinds::from1(interner, VariableKind::Ty(TyVariableKind::General));
-        Binders { binders, value }
-    }
-
-    /// Returns the number of binders.
-    pub fn len(&self, interner: T::Interner) -> usize {
-        self.binders.len(interner)
-    }
-}
-
-impl<T, I> Binders<Binders<T>>
-where
-    T: TypeFoldable<I> + HasInterner<Interner = I>,
-    I: Interner,
-{
-    /// This turns two levels of binders (`for<A> for<B>`) into one level (`for<A, B>`).
-    pub fn fuse_binders(self, interner: T::Interner) -> Binders<T> {
-        let num_binders = self.len(interner);
-        // generate a substitution to shift the indexes of the inner binder:
-        let subst = Substitution::from_iter(
-            interner,
-            self.value
-                .binders
-                .iter(interner)
-                .enumerate()
-                .map(|(i, pk)| (i + num_binders, pk).to_generic_arg(interner)),
-        );
-        let binders = VariableKinds::from_iter(
-            interner,
-            self.binders
-                .iter(interner)
-                .chain(self.value.binders.iter(interner))
-                .cloned(),
-        );
-        let value = self.value.substitute(interner, &subst);
-        Binders { binders, value }
-    }
-}
-
-impl<T: HasInterner> From<Binders<T>> for (VariableKinds<T::Interner>, T) {
-    fn from(binders: Binders<T>) -> Self {
-        (binders.binders, binders.value)
-    }
-}
-
-impl<T, I> Binders<T>
-where
-    T: TypeFoldable<I> + HasInterner<Interner = I>,
-    I: Interner,
-{
-    /// Substitute `parameters` for the variables introduced by these
-    /// binders. So if the binders represent (e.g.) `<X, Y> { T }` and
-    /// parameters is the slice `[A, B]`, then returns `[X => A, Y =>
-    /// B] T`.
-    pub fn substitute(self, interner: I, parameters: &(impl AsParameters<I> + ?Sized)) -> T {
-        let parameters = parameters.as_parameters(interner);
-        assert_eq!(self.binders.len(interner), parameters.len());
-        Subst::apply(interner, parameters, self.value)
-    }
-}
-
-/// Allows iterating over a Binders<Vec<T>>, for instance.
-/// Each element will include the same set of parameter bounds.
-impl<V, U> IntoIterator for Binders<V>
-where
-    V: HasInterner + IntoIterator<Item = U>,
-    U: HasInterner<Interner = V::Interner>,
-{
-    type Item = Binders<U>;
-    type IntoIter = BindersIntoIterator<V>;
-
-    fn into_iter(self) -> Self::IntoIter {
-        BindersIntoIterator {
-            iter: self.value.into_iter(),
-            binders: self.binders,
-        }
-    }
-}
-
-/// `IntoIterator` for binders.
-pub struct BindersIntoIterator<V: HasInterner + IntoIterator> {
-    iter: <V as IntoIterator>::IntoIter,
-    binders: VariableKinds<V::Interner>,
-}
-
-impl<V> Iterator for BindersIntoIterator<V>
-where
-    V: HasInterner + IntoIterator,
-    <V as IntoIterator>::Item: HasInterner<Interner = V::Interner>,
-{
-    type Item = Binders<<V as IntoIterator>::Item>;
-    fn next(&mut self) -> Option<Self::Item> {
-        self.iter
-            .next()
-            .map(|v| Binders::new(self.binders.clone(), v))
-    }
-}
-
-/// Represents one clause of the form `consequence :- conditions` where
-/// `conditions = cond_1 && cond_2 && ...` is the conjunction of the individual
-/// conditions.
-#[derive(Clone, PartialEq, Eq, Hash, TypeFoldable, TypeVisitable, HasInterner, Zip)]
-pub struct ProgramClauseImplication<I: Interner> {
-    /// The consequence of the clause, which holds if the conditions holds.
-    pub consequence: DomainGoal<I>,
-
-    /// The condition goals that should hold.
-    pub conditions: Goals<I>,
-
-    /// The lifetime constraints that should be proven.
-    pub constraints: Constraints<I>,
-
-    /// The relative priority of the implication.
-    pub priority: ClausePriority,
-}
-
-/// Specifies how important an implication is.
-#[derive(Copy, Clone, PartialEq, Eq, Hash, Debug)]
-pub enum ClausePriority {
-    /// High priority, the solver should prioritize this.
-    High,
-
-    /// Low priority, this implication has lower chance to be relevant to the goal.
-    Low,
-}
-
-impl std::ops::BitAnd for ClausePriority {
-    type Output = ClausePriority;
-    fn bitand(self, rhs: ClausePriority) -> Self::Output {
-        match (self, rhs) {
-            (ClausePriority::High, ClausePriority::High) => ClausePriority::High,
-            _ => ClausePriority::Low,
-        }
-    }
-}
-
-/// Contains the data for a program clause.
-#[derive(Clone, PartialEq, Eq, Hash, TypeFoldable, HasInterner, Zip)]
-pub struct ProgramClauseData<I: Interner>(pub Binders<ProgramClauseImplication<I>>);
-
-impl<I: Interner> ProgramClauseImplication<I> {
-    /// Change the implication into an application holding a `FromEnv` goal.
-    pub fn into_from_env_clause(self, interner: I) -> ProgramClauseImplication<I> {
-        if self.conditions.is_empty(interner) {
-            ProgramClauseImplication {
-                consequence: self.consequence.into_from_env_goal(interner),
-                conditions: self.conditions.clone(),
-                constraints: self.constraints.clone(),
-                priority: self.priority,
-            }
-        } else {
-            self
-        }
-    }
-}
-
-impl<I: Interner> ProgramClauseData<I> {
-    /// Change the program clause data into a `FromEnv` program clause.
-    pub fn into_from_env_clause(self, interner: I) -> ProgramClauseData<I> {
-        ProgramClauseData(self.0.map(|i| i.into_from_env_clause(interner)))
-    }
-
-    /// Intern the program clause data.
-    pub fn intern(self, interner: I) -> ProgramClause<I> {
-        ProgramClause {
-            interned: interner.intern_program_clause(self),
-        }
-    }
-}
-
-/// A program clause is a logic expression used to describe a part of the program.
-#[derive(Copy, Clone, PartialEq, Eq, Hash, PartialOrd, Ord, HasInterner)]
-pub struct ProgramClause<I: Interner> {
-    interned: I::InternedProgramClause,
-}
-
-impl<I: Interner> ProgramClause<I> {
-    /// Create a new program clause using `ProgramClauseData`.
-    pub fn new(interner: I, clause: ProgramClauseData<I>) -> Self {
-        let interned = interner.intern_program_clause(clause);
-        Self { interned }
-    }
-
-    /// Change the clause into a `FromEnv` clause.
-    pub fn into_from_env_clause(self, interner: I) -> ProgramClause<I> {
-        let program_clause_data = self.data(interner);
-        let new_clause = program_clause_data.clone().into_from_env_clause(interner);
-        Self::new(interner, new_clause)
-    }
-
-    /// Get the interned program clause.
-    pub fn interned(&self) -> &I::InternedProgramClause {
-        &self.interned
-    }
-
-    /// Get the program clause data.
-    pub fn data(&self, interner: I) -> &ProgramClauseData<I> {
-        interner.program_clause_data(&self.interned)
-    }
-}
-
-/// Wraps a "canonicalized item". Items are canonicalized as follows:
-///
-/// All unresolved existential variables are "renumbered" according to their
-/// first appearance; the kind/universe of the variable is recorded in the
-/// `binders` field.
-#[derive(Clone, Debug, PartialEq, Eq, Hash)]
-pub struct Canonical<T: HasInterner> {
-    /// The item that is canonicalized.
-    pub value: T,
-
-    /// The kind/universe of the variable.
-    pub binders: CanonicalVarKinds<T::Interner>,
-}
-
-impl<T: HasInterner> HasInterner for Canonical<T> {
-    type Interner = T::Interner;
-}
-
-/// A "universe canonical" value. This is a wrapper around a
-/// `Canonical`, indicating that the universes within have been
-/// "renumbered" to start from 0 and collapse unimportant
-/// distinctions.
-///
-/// To produce one of these values, use the `u_canonicalize` method.
-#[derive(Clone, Debug, PartialEq, Eq, Hash)]
-pub struct UCanonical<T: HasInterner> {
-    /// The wrapped `Canonical`.
-    pub canonical: Canonical<T>,
-
-    /// The number of universes that have been collapsed.
-    pub universes: usize,
-}
-
-impl<T: HasInterner> UCanonical<T> {
-    /// Checks whether the universe canonical value is a trivial
-    /// substitution (e.g. an identity substitution).
-    pub fn is_trivial_substitution(
-        &self,
-        interner: T::Interner,
-        canonical_subst: &Canonical<AnswerSubst<T::Interner>>,
-    ) -> bool {
-        let subst = &canonical_subst.value.subst;
-        assert_eq!(
-            self.canonical.binders.len(interner),
-            subst.as_slice(interner).len()
-        );
-        subst.is_identity_subst(interner)
-    }
-
-    /// Creates an identity substitution.
-    pub fn trivial_substitution(&self, interner: T::Interner) -> Substitution<T::Interner> {
-        let binders = &self.canonical.binders;
-        Substitution::from_iter(
-            interner,
-            binders
-                .iter(interner)
-                .enumerate()
-                .map(|(index, pk)| {
-                    let bound_var = BoundVar::new(DebruijnIndex::INNERMOST, index);
-                    match &pk.kind {
-                        VariableKind::Ty(_) => {
-                            GenericArgData::Ty(TyKind::BoundVar(bound_var).intern(interner))
-                                .intern(interner)
-                        }
-                        VariableKind::Lifetime => GenericArgData::Lifetime(
-                            LifetimeData::BoundVar(bound_var).intern(interner),
-                        )
-                        .intern(interner),
-                        VariableKind::Const(ty) => GenericArgData::Const(
-                            ConstData {
-                                ty: ty.clone(),
-                                value: ConstValue::BoundVar(bound_var),
-                            }
-                            .intern(interner),
-                        )
-                        .intern(interner),
-                    }
-                })
-                .collect::<Vec<_>>(),
-        )
-    }
-}
-
-#[derive(Copy, Clone, PartialEq, Eq, Hash, PartialOrd, Ord, HasInterner)]
-/// A general goal; this is the full range of questions you can pose to Chalk.
-pub struct Goal<I: Interner> {
-    interned: I::InternedGoal,
-}
-
-impl<I: Interner> Goal<I> {
-    /// Create a new goal using `GoalData`.
-    pub fn new(interner: I, interned: GoalData<I>) -> Self {
-        let interned = I::intern_goal(interner, interned);
-        Self { interned }
-    }
-
-    /// Gets the interned goal.
-    pub fn interned(&self) -> &I::InternedGoal {
-        &self.interned
-    }
-
-    /// Gets the interned goal data.
-    pub fn data(&self, interner: I) -> &GoalData<I> {
-        interner.goal_data(&self.interned)
-    }
-
-    /// Create a goal using a `forall` or `exists` quantifier.
-    pub fn quantify(self, interner: I, kind: QuantifierKind, binders: VariableKinds<I>) -> Goal<I> {
-        GoalData::Quantified(kind, Binders::new(binders, self)).intern(interner)
-    }
-
-    /// Takes a goal `G` and turns it into `not { G }`.
-    pub fn negate(self, interner: I) -> Self {
-        GoalData::Not(self).intern(interner)
-    }
-
-    /// Takes a goal `G` and turns it into `compatible { G }`.
-    pub fn compatible(self, interner: I) -> Self {
-        // compatible { G } desugars into: forall<T> { if (Compatible, DownstreamType(T)) { G } }
-        // This activates the compatible modality rules and introduces an anonymous downstream type
-        GoalData::Quantified(
-            QuantifierKind::ForAll,
-            Binders::with_fresh_type_var(interner, |ty| {
-                GoalData::Implies(
-                    ProgramClauses::from_iter(
-                        interner,
-                        vec![DomainGoal::Compatible, DomainGoal::DownstreamType(ty)],
-                    ),
-                    self.shifted_in(interner),
-                )
-                .intern(interner)
-            }),
-        )
-        .intern(interner)
-    }
-
-    /// Create an implication goal that holds if the predicates are true.
-    pub fn implied_by(self, interner: I, predicates: ProgramClauses<I>) -> Goal<I> {
-        GoalData::Implies(predicates, self).intern(interner)
-    }
-
-    /// True if this goal is "trivially true" -- i.e., no work is
-    /// required to prove it.
-    pub fn is_trivially_true(&self, interner: I) -> bool {
-        match self.data(interner) {
-            GoalData::All(goals) => goals.is_empty(interner),
-            _ => false,
-        }
-    }
-}
-
-impl<I> Goal<I>
-where
-    I: Interner,
-{
-    /// Creates a single goal that only holds if a list of goals holds.
-    pub fn all<II>(interner: I, iter: II) -> Self
-    where
-        II: IntoIterator<Item = Goal<I>>,
-    {
-        let mut iter = iter.into_iter();
-        if let Some(goal0) = iter.next() {
-            if let Some(goal1) = iter.next() {
-                // More than one goal to prove
-                let goals = Goals::from_iter(
-                    interner,
-                    Some(goal0).into_iter().chain(Some(goal1)).chain(iter),
-                );
-                GoalData::All(goals).intern(interner)
-            } else {
-                // One goal to prove
-                goal0
-            }
-        } else {
-            // No goals to prove, always true
-            GoalData::All(Goals::empty(interner)).intern(interner)
-        }
-    }
-}
-
-#[derive(Clone, PartialEq, Eq, Hash, TypeFoldable, TypeVisitable, HasInterner, Zip)]
-/// A general goal; this is the full range of questions you can pose to Chalk.
-pub enum GoalData<I: Interner> {
-    /// Introduces a binding at depth 0, shifting other bindings up
-    /// (deBruijn index).
-    Quantified(QuantifierKind, Binders<Goal<I>>),
-
-    /// A goal that holds given some clauses (like an if-statement).
-    Implies(ProgramClauses<I>, Goal<I>),
-
-    /// List of goals that all should hold.
-    All(Goals<I>),
-
-    /// Negation: the inner goal should not hold.
-    Not(Goal<I>),
-
-    /// Make two things equal; the rules for doing so are well known to the logic
-    EqGoal(EqGoal<I>),
-
-    /// Make one thing a subtype of another; the rules for doing so are well known to the logic
-    SubtypeGoal(SubtypeGoal<I>),
-
-    /// A "domain goal" indicates some base sort of goal that can be
-    /// proven via program clauses
-    DomainGoal(DomainGoal<I>),
-
-    /// Indicates something that cannot be proven to be true or false
-    /// definitively. This can occur with overflow but also with
-    /// unifications of skolemized variables like `forall<X,Y> { X = Y
-    /// }`. Of course, that statement is false, as there exist types
-    /// X, Y where `X = Y` is not true. But we treat it as "cannot
-    /// prove" so that `forall<X,Y> { not { X = Y } }` also winds up
-    /// as cannot prove.
-    CannotProve,
-}
-
-impl<I: Interner> Copy for GoalData<I>
-where
-    I::InternedType: Copy,
-    I::InternedLifetime: Copy,
-    I::InternedGenericArg: Copy,
-    I::InternedSubstitution: Copy,
-    I::InternedGoal: Copy,
-    I::InternedGoals: Copy,
-    I::InternedProgramClauses: Copy,
-    I::InternedVariableKinds: Copy,
-{
-}
-
-impl<I: Interner> GoalData<I> {
-    /// Create an interned goal.
-    pub fn intern(self, interner: I) -> Goal<I> {
-        Goal::new(interner, self)
-    }
-}
-
-/// Kinds of quantifiers in the logic, such as `forall` and `exists`.
-#[derive(Copy, Clone, Debug, PartialEq, Eq, Hash, PartialOrd, Ord)]
-pub enum QuantifierKind {
-    /// Universal quantifier `ForAll`.
-    ///
-    /// A formula with the universal quantifier `forall(x). P(x)` is satisfiable
-    /// if and only if the subformula `P(x)` is true for all possible values for x.
-    ForAll,
-
-    /// Existential quantifier `Exists`.
-    ///
-    /// A formula with the existential quantifier `exists(x). P(x)` is satisfiable
-    /// if and only if there exists at least one value for all possible values of x
-    /// which satisfies the subformula `P(x)`.
-
-    /// In the context of chalk, the existential quantifier usually demands the
-    /// existence of exactly one instance (i.e. type) that satisfies the formula
-    /// (i.e. type constraints). More than one instance means that the result is ambiguous.
-    Exists,
-}
-
-/// A constraint on lifetimes.
-///
-/// When we search for solutions within the trait system, we essentially ignore
-/// lifetime constraints, instead gathering them up to return with our solution
-/// for later checking. This allows for decoupling between type and region
-/// checking in the compiler.
-#[derive(Clone, PartialEq, Eq, Hash, TypeFoldable, TypeVisitable, HasInterner, Zip)]
-pub enum Constraint<I: Interner> {
-    /// Outlives constraint `'a: 'b`, indicating that the value of `'a` must be
-    /// a superset of the value of `'b`.
-    LifetimeOutlives(Lifetime<I>, Lifetime<I>),
-
-    /// Type outlives constraint `T: 'a`, indicating that the type `T` must live
-    /// at least as long as the value of `'a`.
-    TypeOutlives(Ty<I>, Lifetime<I>),
-}
-
-impl<I: Interner> Copy for Constraint<I>
-where
-    I::InternedLifetime: Copy,
-    I::InternedType: Copy,
-{
-}
-
-impl<I: Interner> Substitution<I> {
-    /// A substitution is an **identity substitution** if it looks
-    /// like this
-    ///
-    /// ```text
-    /// ?0 := ?0
-    /// ?1 := ?1
-    /// ?2 := ?2
-    /// ...
-    /// ```
-    ///
-    /// Basically, each value is mapped to a type or lifetime with its
-    /// same index.
-    pub fn is_identity_subst(&self, interner: I) -> bool {
-        self.iter(interner).zip(0..).all(|(generic_arg, index)| {
-            let index_db = BoundVar::new(DebruijnIndex::INNERMOST, index);
-            match generic_arg.data(interner) {
-                GenericArgData::Ty(ty) => match ty.kind(interner) {
-                    TyKind::BoundVar(depth) => index_db == *depth,
-                    _ => false,
-                },
-                GenericArgData::Lifetime(lifetime) => match lifetime.data(interner) {
-                    LifetimeData::BoundVar(depth) => index_db == *depth,
-                    _ => false,
-                },
-                GenericArgData::Const(constant) => match &constant.data(interner).value {
-                    ConstValue::BoundVar(depth) => index_db == *depth,
-                    _ => false,
-                },
-            }
-        })
-    }
-
-    /// Apply the substitution to a value.
-    pub fn apply<T>(&self, value: T, interner: I) -> T
-    where
-        T: TypeFoldable<I>,
-    {
-        Substitute::apply(self, value, interner)
-    }
-
-    /// Gets an iterator of all type parameters.
-    pub fn type_parameters(&self, interner: I) -> impl Iterator<Item = Ty<I>> + '_ {
-        self.iter(interner)
-            .filter_map(move |p| p.ty(interner))
-            .cloned()
-    }
-
-    /// Compute type flags for Substitution<I>
-    fn compute_flags(&self, interner: I) -> TypeFlags {
-        let mut flags = TypeFlags::empty();
-        for generic_arg in self.iter(interner) {
-            flags |= generic_arg.compute_flags(interner);
-        }
-        flags
-    }
-}
-
-#[derive(FallibleTypeFolder)]
-struct SubstFolder<'i, I: Interner, A: AsParameters<I>> {
-    interner: I,
-    subst: &'i A,
-}
-
-impl<I: Interner, A: AsParameters<I>> SubstFolder<'_, I, A> {
-    /// Index into the list of parameters.
-    pub fn at(&self, index: usize) -> &GenericArg<I> {
-        let interner = self.interner;
-        &self.subst.as_parameters(interner)[index]
-    }
-}
-
-/// Convert a value to a list of parameters.
-pub trait AsParameters<I: Interner> {
-    /// Convert the current value to parameters.
-    fn as_parameters(&self, interner: I) -> &[GenericArg<I>];
-}
-
-impl<I: Interner> AsParameters<I> for Substitution<I> {
-    #[allow(unreachable_code, unused_variables)]
-    fn as_parameters(&self, interner: I) -> &[GenericArg<I>] {
-        self.as_slice(interner)
-    }
-}
-
-impl<I: Interner> AsParameters<I> for [GenericArg<I>] {
-    fn as_parameters(&self, _interner: I) -> &[GenericArg<I>] {
-        self
-    }
-}
-
-impl<I: Interner> AsParameters<I> for [GenericArg<I>; 1] {
-    fn as_parameters(&self, _interner: I) -> &[GenericArg<I>] {
-        self
-    }
-}
-
-impl<I: Interner> AsParameters<I> for Vec<GenericArg<I>> {
-    fn as_parameters(&self, _interner: I) -> &[GenericArg<I>] {
-        self
-    }
-}
-
-impl<T, I: Interner> AsParameters<I> for &T
-where
-    T: ?Sized + AsParameters<I>,
-{
-    fn as_parameters(&self, interner: I) -> &[GenericArg<I>] {
-        T::as_parameters(self, interner)
-    }
-}
-
-/// An extension trait to anything that can be represented as list of `GenericArg`s that signifies
-/// that it can applied as a substituion to a value
-pub trait Substitute<I: Interner>: AsParameters<I> {
-    /// Apply the substitution to a value.
-    fn apply<T: TypeFoldable<I>>(&self, value: T, interner: I) -> T;
-}
-
-impl<I: Interner, A: AsParameters<I>> Substitute<I> for A {
-    fn apply<T>(&self, value: T, interner: I) -> T
-    where
-        T: TypeFoldable<I>,
-    {
-        value
-            .try_fold_with(
-                &mut SubstFolder {
-                    interner,
-                    subst: self,
-                },
-                DebruijnIndex::INNERMOST,
-            )
-            .unwrap()
-    }
-}
-
-/// Utility for converting a list of all the binders into scope
-/// into references to those binders. Simply pair the binders with
-/// the indices, and invoke `to_generic_arg()` on the `(binder,
-/// index)` pair. The result will be a reference to a bound
-/// variable of appropriate kind at the corresponding index.
-pub trait ToGenericArg<I: Interner> {
-    /// Converts the binders in scope to references to those binders.
-    fn to_generic_arg(&self, interner: I) -> GenericArg<I> {
-        self.to_generic_arg_at_depth(interner, DebruijnIndex::INNERMOST)
-    }
-
-    /// Converts the binders at the specified depth to references to those binders.
-    fn to_generic_arg_at_depth(&self, interner: I, debruijn: DebruijnIndex) -> GenericArg<I>;
-}
-
-impl<'a, I: Interner> ToGenericArg<I> for (usize, &'a VariableKind<I>) {
-    fn to_generic_arg_at_depth(&self, interner: I, debruijn: DebruijnIndex) -> GenericArg<I> {
-        let &(index, binder) = self;
-        let bound_var = BoundVar::new(debruijn, index);
-        binder.to_bound_variable(interner, bound_var)
-    }
-}
-
-impl<'i, I: Interner, A: AsParameters<I>> TypeFolder<I> for SubstFolder<'i, I, A> {
-    fn as_dyn(&mut self) -> &mut dyn TypeFolder<I> {
-        self
-    }
-
-    fn fold_free_var_ty(&mut self, bound_var: BoundVar, outer_binder: DebruijnIndex) -> Ty<I> {
-        assert_eq!(bound_var.debruijn, DebruijnIndex::INNERMOST);
-        let ty = self.at(bound_var.index);
-        let ty = ty.assert_ty_ref(TypeFolder::interner(self));
-        ty.clone()
-            .shifted_in_from(TypeFolder::interner(self), outer_binder)
-    }
-
-    fn fold_free_var_lifetime(
-        &mut self,
-        bound_var: BoundVar,
-        outer_binder: DebruijnIndex,
-    ) -> Lifetime<I> {
-        assert_eq!(bound_var.debruijn, DebruijnIndex::INNERMOST);
-        let l = self.at(bound_var.index);
-        let l = l.assert_lifetime_ref(TypeFolder::interner(self));
-        l.clone()
-            .shifted_in_from(TypeFolder::interner(self), outer_binder)
-    }
-
-    fn fold_free_var_const(
-        &mut self,
-        _ty: Ty<I>,
-        bound_var: BoundVar,
-        outer_binder: DebruijnIndex,
-    ) -> Const<I> {
-        assert_eq!(bound_var.debruijn, DebruijnIndex::INNERMOST);
-        let c = self.at(bound_var.index);
-        let c = c.assert_const_ref(TypeFolder::interner(self));
-        c.clone()
-            .shifted_in_from(TypeFolder::interner(self), outer_binder)
-    }
-
-    fn interner(&self) -> I {
-        self.interner
-    }
-}
-
-macro_rules! interned_slice_common {
-    ($seq:ident, $data:ident => $elem:ty, $intern:ident => $interned:ident) => {
-        /// List of interned elements.
-        #[derive(Copy, Clone, PartialEq, Eq, Hash, PartialOrd, Ord, HasInterner)]
-        pub struct $seq<I: Interner> {
-            interned: I::$interned,
-        }
-
-        impl<I: Interner> $seq<I> {
-            /// Get the interned elements.
-            pub fn interned(&self) -> &I::$interned {
-                &self.interned
-            }
-
-            /// Returns a slice containing the elements.
-            pub fn as_slice(&self, interner: I) -> &[$elem] {
-                Interner::$data(interner, &self.interned)
-            }
-
-            /// Index into the sequence.
-            pub fn at(&self, interner: I, index: usize) -> &$elem {
-                &self.as_slice(interner)[index]
-            }
-
-            /// Create an empty sequence.
-            pub fn empty(interner: I) -> Self {
-                Self::from_iter(interner, None::<$elem>)
-            }
-
-            /// Check whether this is an empty sequence.
-            pub fn is_empty(&self, interner: I) -> bool {
-                self.as_slice(interner).is_empty()
-            }
-
-            /// Get an iterator over the elements of the sequence.
-            pub fn iter(&self, interner: I) -> std::slice::Iter<'_, $elem> {
-                self.as_slice(interner).iter()
-            }
-
-            /// Get the length of the sequence.
-            pub fn len(&self, interner: I) -> usize {
-                self.as_slice(interner).len()
-            }
-        }
-    };
-}
-
-macro_rules! interned_slice {
-    ($seq:ident, $data:ident => $elem:ty, $intern:ident => $interned:ident) => {
-        interned_slice_common!($seq, $data => $elem, $intern => $interned);
-
-        impl<I: Interner> $seq<I> {
-            /// Tries to create a sequence using an iterator of element-like things.
-            pub fn from_fallible<E>(
-                interner: I,
-                elements: impl IntoIterator<Item = Result<impl CastTo<$elem>, E>>,
-            ) -> Result<Self, E> {
-                Ok(Self {
-                    interned: I::$intern(interner, elements.into_iter().casted(interner))?,
-                })
-            }
-
-            /// Create a sequence from elements
-            pub fn from_iter(
-                interner: I,
-                elements: impl IntoIterator<Item = impl CastTo<$elem>>,
-            ) -> Self {
-                Self::from_fallible(
-                    interner,
-                    elements
-                        .into_iter()
-                        .map(|el| -> Result<$elem, ()> { Ok(el.cast(interner)) }),
-                )
-                .unwrap()
-            }
-
-            /// Create a sequence from a single element.
-            pub fn from1(interner: I, element: impl CastTo<$elem>) -> Self {
-                Self::from_iter(interner, Some(element))
-            }
-        }
-    };
-}
-
-interned_slice!(
-    QuantifiedWhereClauses,
-    quantified_where_clauses_data => QuantifiedWhereClause<I>,
-    intern_quantified_where_clauses => InternedQuantifiedWhereClauses
-);
-
-interned_slice!(
-    ProgramClauses,
-    program_clauses_data => ProgramClause<I>,
-    intern_program_clauses => InternedProgramClauses
-);
-
-interned_slice!(
-    VariableKinds,
-    variable_kinds_data => VariableKind<I>,
-    intern_generic_arg_kinds => InternedVariableKinds
-);
-
-interned_slice!(
-    CanonicalVarKinds,
-    canonical_var_kinds_data => CanonicalVarKind<I>,
-    intern_canonical_var_kinds => InternedCanonicalVarKinds
-);
-
-interned_slice!(Goals, goals_data => Goal<I>, intern_goals => InternedGoals);
-
-interned_slice!(
-    Constraints,
-    constraints_data => InEnvironment<Constraint<I>>,
-    intern_constraints => InternedConstraints
-);
-
-interned_slice!(
-    Substitution,
-    substitution_data => GenericArg<I>,
-    intern_substitution => InternedSubstitution
-);
-
-interned_slice_common!(
-    Variances,
-    variances_data => Variance,
-    intern_variance => InternedVariances
-);
-
-impl<I: Interner> Variances<I> {
-    /// Tries to create a list of canonical variable kinds using an iterator.
-    pub fn from_fallible<E>(
-        interner: I,
-        variances: impl IntoIterator<Item = Result<Variance, E>>,
-    ) -> Result<Self, E> {
-        Ok(Variances {
-            interned: I::intern_variances(interner, variances.into_iter())?,
-        })
-    }
-
-    /// Creates a list of canonical variable kinds using an iterator.
-    pub fn from_iter(interner: I, variances: impl IntoIterator<Item = Variance>) -> Self {
-        Self::from_fallible(
-            interner,
-            variances
-                .into_iter()
-                .map(|p| -> Result<Variance, ()> { Ok(p) }),
-        )
-        .unwrap()
-    }
-
-    /// Creates a list of canonical variable kinds from a single canonical variable kind.
-    pub fn from1(interner: I, variance: Variance) -> Self {
-        Self::from_iter(interner, Some(variance))
-    }
-}
-
-/// Combines a substitution (`subst`) with a set of region constraints
-/// (`constraints`). This represents the result of a query; the
-/// substitution stores the values for the query's unknown variables,
-/// and the constraints represents any region constraints that must
-/// additionally be solved.
-#[derive(Clone, Debug, PartialEq, Eq, Hash, TypeFoldable, TypeVisitable, HasInterner)]
-pub struct ConstrainedSubst<I: Interner> {
-    /// The substitution that is being constrained.
-    ///
-    /// NB: The `is_trivial` routine relies on the fact that `subst` is folded first.
-    pub subst: Substitution<I>,
-
-    /// Region constraints that constrain the substitution.
-    pub constraints: Constraints<I>,
-}
-
-/// The resulting substitution after solving a goal.
-#[derive(Clone, Debug, PartialEq, Eq, Hash, TypeFoldable, TypeVisitable, HasInterner)]
-pub struct AnswerSubst<I: Interner> {
-    /// The substitution result.
-    ///
-    /// NB: The `is_trivial` routine relies on the fact that `subst` is folded first.
-    pub subst: Substitution<I>,
-
-    /// List of constraints that are part of the answer.
-    pub constraints: Constraints<I>,
-
-    /// Delayed subgoals, used when the solver answered with an (incomplete) `Answer` (instead of a `CompleteAnswer`).
-    pub delayed_subgoals: Vec<InEnvironment<Goal<I>>>,
-}
-
-/// Logic to decide the Variance for a given subst
-pub trait UnificationDatabase<I>
-where
-    Self: std::fmt::Debug,
-    I: Interner,
-{
-    /// Gets the variances for the substitution of a fn def
-    fn fn_def_variance(&self, fn_def_id: FnDefId<I>) -> Variances<I>;
-
-    /// Gets the variances for the substitution of a adt
-    fn adt_variance(&self, adt_id: AdtId<I>) -> Variances<I>;
-}
diff --git a/vendor/chalk-ir/src/visit.rs b/vendor/chalk-ir/src/visit.rs
deleted file mode 100644
index c761ab46f..000000000
--- a/vendor/chalk-ir/src/visit.rs
+++ /dev/null
@@ -1,422 +0,0 @@
-//! 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)
-    }
-}
diff --git a/vendor/chalk-ir/src/visit/binder_impls.rs b/vendor/chalk-ir/src/visit/binder_impls.rs
deleted file mode 100644
index 709f99044..000000000
--- a/vendor/chalk-ir/src/visit/binder_impls.rs
+++ /dev/null
@@ -1,47 +0,0 @@
-//! This module contains impls of `TypeVisitable` for those types that
-//! introduce binders.
-//!
-//! The more interesting impls of `TypeVisitable` remain in the `visit` module.
-
-use crate::interner::HasInterner;
-use crate::{
-    Binders, Canonical, ControlFlow, DebruijnIndex, FnPointer, Interner, TypeVisitable, TypeVisitor,
-};
-
-impl<I: Interner> TypeVisitable<I> for FnPointer<I> {
-    fn visit_with<B>(
-        &self,
-        visitor: &mut dyn TypeVisitor<I, BreakTy = B>,
-        outer_binder: DebruijnIndex,
-    ) -> ControlFlow<B> {
-        self.substitution
-            .visit_with(visitor, outer_binder.shifted_in())
-    }
-}
-
-impl<T, I: Interner> TypeVisitable<I> for Binders<T>
-where
-    T: HasInterner + TypeVisitable<I>,
-{
-    fn visit_with<B>(
-        &self,
-        visitor: &mut dyn TypeVisitor<I, BreakTy = B>,
-        outer_binder: DebruijnIndex,
-    ) -> ControlFlow<B> {
-        self.value.visit_with(visitor, outer_binder.shifted_in())
-    }
-}
-
-impl<I, T> TypeVisitable<I> for Canonical<T>
-where
-    I: Interner,
-    T: HasInterner<Interner = I> + TypeVisitable<I>,
-{
-    fn visit_with<B>(
-        &self,
-        visitor: &mut dyn TypeVisitor<I, BreakTy = B>,
-        outer_binder: DebruijnIndex,
-    ) -> ControlFlow<B> {
-        self.value.visit_with(visitor, outer_binder.shifted_in())
-    }
-}
diff --git a/vendor/chalk-ir/src/visit/boring_impls.rs b/vendor/chalk-ir/src/visit/boring_impls.rs
deleted file mode 100644
index 512d9ecd8..000000000
--- a/vendor/chalk-ir/src/visit/boring_impls.rs
+++ /dev/null
@@ -1,261 +0,0 @@
-//! This module contains "rote and uninteresting" impls of `TypeVisitable` for
-//! various types. In general, we prefer to derive `TypeVisitable`, but
-//! sometimes that doesn't work for whatever reason.
-//!
-//! The more interesting impls of `TypeVisitable` remain in the `visit` module.
-
-use crate::{
-    try_break, AdtId, AssocTypeId, ClausePriority, ClosureId, Constraints, ControlFlow,
-    DebruijnIndex, FloatTy, FnDefId, ForeignDefId, GeneratorId, GenericArg, Goals, ImplId, IntTy,
-    Interner, Mutability, OpaqueTyId, PlaceholderIndex, ProgramClause, ProgramClauses,
-    QuantifiedWhereClauses, QuantifierKind, Safety, Scalar, Substitution, TraitId,
-    TypeSuperVisitable, TypeVisitable, TypeVisitor, UintTy, UniverseIndex,
-};
-use std::{marker::PhantomData, sync::Arc};
-
-/// Convenience function to visit all the items in the iterator it.
-pub fn visit_iter<'i, T, I, B>(
-    it: impl Iterator<Item = T>,
-    visitor: &mut dyn TypeVisitor<I, BreakTy = B>,
-    outer_binder: DebruijnIndex,
-) -> ControlFlow<B>
-where
-    T: TypeVisitable<I>,
-    I: 'i + Interner,
-{
-    for e in it {
-        try_break!(e.visit_with(visitor, outer_binder));
-    }
-    ControlFlow::Continue(())
-}
-
-impl<T: TypeVisitable<I>, I: Interner> TypeVisitable<I> for &T {
-    fn visit_with<B>(
-        &self,
-        visitor: &mut dyn TypeVisitor<I, BreakTy = B>,
-        outer_binder: DebruijnIndex,
-    ) -> ControlFlow<B> {
-        T::visit_with(self, visitor, outer_binder)
-    }
-}
-
-impl<T: TypeVisitable<I>, I: Interner> TypeVisitable<I> for Vec<T> {
-    fn visit_with<B>(
-        &self,
-        visitor: &mut dyn TypeVisitor<I, BreakTy = B>,
-        outer_binder: DebruijnIndex,
-    ) -> ControlFlow<B> {
-        visit_iter(self.iter(), visitor, outer_binder)
-    }
-}
-
-impl<T: TypeVisitable<I>, I: Interner> TypeVisitable<I> for &[T] {
-    fn visit_with<B>(
-        &self,
-        visitor: &mut dyn TypeVisitor<I, BreakTy = B>,
-        outer_binder: DebruijnIndex,
-    ) -> ControlFlow<B> {
-        visit_iter(self.iter(), visitor, outer_binder)
-    }
-}
-
-impl<T: TypeVisitable<I>, I: Interner> TypeVisitable<I> for Box<T> {
-    fn visit_with<B>(
-        &self,
-        visitor: &mut dyn TypeVisitor<I, BreakTy = B>,
-        outer_binder: DebruijnIndex,
-    ) -> ControlFlow<B> {
-        T::visit_with(self, visitor, outer_binder)
-    }
-}
-
-impl<T: TypeVisitable<I>, I: Interner> TypeVisitable<I> for Arc<T> {
-    fn visit_with<B>(
-        &self,
-        visitor: &mut dyn TypeVisitor<I, BreakTy = B>,
-        outer_binder: DebruijnIndex,
-    ) -> ControlFlow<B> {
-        T::visit_with(self, visitor, outer_binder)
-    }
-}
-
-macro_rules! tuple_visit {
-    ($($n:ident),*) => {
-        impl<$($n: TypeVisitable<I>,)* I: Interner> TypeVisitable<I> for ($($n,)*) {
-            fn visit_with<BT>(&self, visitor: &mut dyn TypeVisitor<I, BreakTy = BT>, outer_binder: DebruijnIndex) -> ControlFlow<BT> {
-                #[allow(non_snake_case)]
-                let &($(ref $n),*) = self;
-                $(
-                    try_break!($n.visit_with(visitor, outer_binder));
-                )*
-                ControlFlow::Continue(())
-            }
-        }
-    }
-}
-
-tuple_visit!(A, B);
-tuple_visit!(A, B, C);
-tuple_visit!(A, B, C, D);
-tuple_visit!(A, B, C, D, E);
-
-impl<T: TypeVisitable<I>, I: Interner> TypeVisitable<I> for Option<T> {
-    fn visit_with<B>(
-        &self,
-        visitor: &mut dyn TypeVisitor<I, BreakTy = B>,
-        outer_binder: DebruijnIndex,
-    ) -> ControlFlow<B> {
-        match self {
-            Some(e) => e.visit_with(visitor, outer_binder),
-            None => ControlFlow::Continue(()),
-        }
-    }
-}
-
-impl<I: Interner> TypeVisitable<I> for GenericArg<I> {
-    fn 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 Substitution<I> {
-    fn visit_with<B>(
-        &self,
-        visitor: &mut dyn TypeVisitor<I, BreakTy = B>,
-        outer_binder: DebruijnIndex,
-    ) -> ControlFlow<B> {
-        let interner = visitor.interner();
-        visit_iter(self.iter(interner), visitor, outer_binder)
-    }
-}
-
-impl<I: Interner> TypeVisitable<I> for Goals<I> {
-    fn visit_with<B>(
-        &self,
-        visitor: &mut dyn TypeVisitor<I, BreakTy = B>,
-        outer_binder: DebruijnIndex,
-    ) -> ControlFlow<B> {
-        let interner = visitor.interner();
-        visit_iter(self.iter(interner), visitor, outer_binder)
-    }
-}
-
-#[doc(hidden)]
-#[macro_export]
-macro_rules! const_visit {
-    ($t:ty) => {
-        impl<I: Interner> $crate::visit::TypeVisitable<I> for $t {
-            fn visit_with<B>(
-                &self,
-                _visitor: &mut dyn ($crate::visit::TypeVisitor<I, BreakTy = B>),
-                _outer_binder: DebruijnIndex,
-            ) -> ControlFlow<B> {
-                ControlFlow::Continue(())
-            }
-        }
-    };
-}
-
-const_visit!(bool);
-const_visit!(usize);
-const_visit!(UniverseIndex);
-const_visit!(PlaceholderIndex);
-const_visit!(QuantifierKind);
-const_visit!(DebruijnIndex);
-const_visit!(ClausePriority);
-const_visit!(());
-const_visit!(Scalar);
-const_visit!(UintTy);
-const_visit!(IntTy);
-const_visit!(FloatTy);
-const_visit!(Mutability);
-const_visit!(Safety);
-
-#[doc(hidden)]
-#[macro_export]
-macro_rules! id_visit {
-    ($t:ident) => {
-        impl<I: Interner> $crate::visit::TypeVisitable<I> for $t<I> {
-            fn visit_with<B>(
-                &self,
-                _visitor: &mut dyn ($crate::visit::TypeVisitor<I, BreakTy = B>),
-                _outer_binder: DebruijnIndex,
-            ) -> ControlFlow<B> {
-                ControlFlow::Continue(())
-            }
-        }
-    };
-}
-
-id_visit!(ImplId);
-id_visit!(AdtId);
-id_visit!(TraitId);
-id_visit!(OpaqueTyId);
-id_visit!(AssocTypeId);
-id_visit!(FnDefId);
-id_visit!(ClosureId);
-id_visit!(GeneratorId);
-id_visit!(ForeignDefId);
-
-impl<I: Interner> TypeSuperVisitable<I> for ProgramClause<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).0.visit_with(visitor, outer_binder)
-    }
-}
-
-impl<I: Interner> TypeVisitable<I> for ProgramClauses<I> {
-    fn visit_with<B>(
-        &self,
-        visitor: &mut dyn TypeVisitor<I, BreakTy = B>,
-        outer_binder: DebruijnIndex,
-    ) -> ControlFlow<B> {
-        let interner = visitor.interner();
-
-        visit_iter(self.iter(interner), visitor, outer_binder)
-    }
-}
-
-impl<I: Interner> TypeVisitable<I> for Constraints<I> {
-    fn visit_with<B>(
-        &self,
-        visitor: &mut dyn TypeVisitor<I, BreakTy = B>,
-        outer_binder: DebruijnIndex,
-    ) -> ControlFlow<B> {
-        let interner = visitor.interner();
-
-        visit_iter(self.iter(interner), visitor, outer_binder)
-    }
-}
-
-impl<I: Interner> TypeVisitable<I> for QuantifiedWhereClauses<I> {
-    fn visit_with<B>(
-        &self,
-        visitor: &mut dyn TypeVisitor<I, BreakTy = B>,
-        outer_binder: DebruijnIndex,
-    ) -> ControlFlow<B> {
-        let interner = visitor.interner();
-
-        visit_iter(self.iter(interner), visitor, outer_binder)
-    }
-}
-
-impl<I: Interner> TypeVisitable<I> for PhantomData<I> {
-    fn visit_with<B>(
-        &self,
-        _visitor: &mut dyn TypeVisitor<I, BreakTy = B>,
-        _outer_binder: DebruijnIndex,
-    ) -> ControlFlow<B> {
-        ControlFlow::Continue(())
-    }
-}
diff --git a/vendor/chalk-ir/src/visit/visitors.rs b/vendor/chalk-ir/src/visit/visitors.rs
deleted file mode 100644
index 51c087840..000000000
--- a/vendor/chalk-ir/src/visit/visitors.rs
+++ /dev/null
@@ -1,41 +0,0 @@
-//! TypeVisitor helpers
-
-use crate::{BoundVar, ControlFlow, DebruijnIndex, Interner, TypeVisitable, TypeVisitor};
-
-/// TypeVisitor extensions.
-pub trait VisitExt<I: Interner>: TypeVisitable<I> {
-    /// Check whether there are free (non-bound) variables.
-    fn has_free_vars(&self, interner: I) -> bool {
-        let flow = self.visit_with(
-            &mut FindFreeVarsVisitor { interner },
-            DebruijnIndex::INNERMOST,
-        );
-        matches!(flow, ControlFlow::Break(_))
-    }
-}
-
-impl<T, I: Interner> VisitExt<I> for T where T: TypeVisitable<I> {}
-
-struct FindFreeVarsVisitor<I: Interner> {
-    interner: I,
-}
-
-impl<I: Interner> TypeVisitor<I> for FindFreeVarsVisitor<I> {
-    type BreakTy = ();
-
-    fn as_dyn(&mut self) -> &mut dyn TypeVisitor<I, BreakTy = Self::BreakTy> {
-        self
-    }
-
-    fn interner(&self) -> I {
-        self.interner
-    }
-
-    fn visit_free_var(
-        &mut self,
-        _bound_var: BoundVar,
-        _outer_binder: DebruijnIndex,
-    ) -> ControlFlow<()> {
-        ControlFlow::Break(())
-    }
-}
diff --git a/vendor/chalk-ir/src/zip.rs b/vendor/chalk-ir/src/zip.rs
deleted file mode 100644
index afa4a13cb..000000000
--- a/vendor/chalk-ir/src/zip.rs
+++ /dev/null
@@ -1,543 +0,0 @@
-//! Traits for "zipping" types, walking through two structures and checking that they match.
-
-use crate::fold::TypeFoldable;
-use crate::*;
-use std::fmt::Debug;
-use std::sync::Arc;
-
-/// When we zip types, we basically traverse the structure, ensuring
-/// that it matches.  When we come to types/lifetimes, we invoke the
-/// callback methods in the zipper to match them up. Primarily used
-/// during unification or similar operations.
-///
-/// So e.g. if you had `A: Eq<B>` zipped with `X: Eq<Y>`, then the zipper
-/// would get two callbacks, one pairing `A` and `X`, and the other pairing
-/// `B` and `Y`.
-///
-/// For things other than types/lifetimes, the zip impls will
-/// guarantee equality. So e.g. if you have `A: Eq<B>` zipped with `X:
-/// Ord<Y>`, you would wind up with an error, no matter what zipper
-/// you are using. This is because the traits `Eq` and `Ord` are
-/// represented by two distinct `ItemId` values, and the impl for
-/// `ItemId` requires that all `ItemId` in the two zipped values match
-/// up.
-pub trait Zipper<I: Interner> {
-    /// Indicates that the two types `a` and `b` were found in matching spots.
-    fn zip_tys(&mut self, variance: Variance, a: &Ty<I>, b: &Ty<I>) -> Fallible<()>;
-
-    /// Indicates that the two lifetimes `a` and `b` were found in matching spots.
-    fn zip_lifetimes(
-        &mut self,
-        variance: Variance,
-        a: &Lifetime<I>,
-        b: &Lifetime<I>,
-    ) -> Fallible<()>;
-
-    /// Indicates that the two consts `a` and `b` were found in matching spots.
-    fn zip_consts(&mut self, variance: Variance, a: &Const<I>, b: &Const<I>) -> Fallible<()>;
-
-    /// Zips two values appearing beneath binders.
-    fn zip_binders<T>(
-        &mut self,
-        variance: Variance,
-        a: &Binders<T>,
-        b: &Binders<T>,
-    ) -> Fallible<()>
-    where
-        T: Clone + HasInterner<Interner = I> + Zip<I> + TypeFoldable<I>;
-
-    /// Zips two substs
-    fn zip_substs(
-        &mut self,
-        ambient: Variance,
-        variances: Option<Variances<I>>,
-        a: &[GenericArg<I>],
-        b: &[GenericArg<I>],
-    ) -> Fallible<()>
-    where
-        Self: Sized,
-    {
-        for (i, (a, b)) in a.iter().zip(b.iter()).enumerate() {
-            let variance = variances
-                .as_ref()
-                .map(|v| v.as_slice(self.interner())[i])
-                .unwrap_or(Variance::Invariant);
-            Zip::zip_with(self, ambient.xform(variance), a, b)?;
-        }
-        Ok(())
-    }
-
-    /// Retrieves the interner from the underlying zipper object
-    fn interner(&self) -> I;
-
-    /// Retrieves the `UnificationDatabase` from the underlying zipper object
-    fn unification_database(&self) -> &dyn UnificationDatabase<I>;
-}
-
-impl<'f, Z, I> Zipper<I> for &'f mut Z
-where
-    I: Interner,
-    Z: Zipper<I>,
-{
-    fn zip_tys(&mut self, variance: Variance, a: &Ty<I>, b: &Ty<I>) -> Fallible<()> {
-        (**self).zip_tys(variance, a, b)
-    }
-
-    fn zip_lifetimes(
-        &mut self,
-        variance: Variance,
-        a: &Lifetime<I>,
-        b: &Lifetime<I>,
-    ) -> Fallible<()> {
-        (**self).zip_lifetimes(variance, a, b)
-    }
-
-    fn zip_consts(&mut self, variance: Variance, a: &Const<I>, b: &Const<I>) -> Fallible<()> {
-        (**self).zip_consts(variance, a, b)
-    }
-
-    fn zip_binders<T>(&mut self, variance: Variance, a: &Binders<T>, b: &Binders<T>) -> Fallible<()>
-    where
-        T: Clone + HasInterner<Interner = I> + Zip<I> + TypeFoldable<I>,
-    {
-        (**self).zip_binders(variance, a, b)
-    }
-
-    fn interner(&self) -> I {
-        Z::interner(*self)
-    }
-
-    fn unification_database(&self) -> &dyn UnificationDatabase<I> {
-        (**self).unification_database()
-    }
-}
-
-/// The `Zip` trait walks two values, invoking the `Zipper` methods where
-/// appropriate, but otherwise requiring strict equality.
-///
-/// See `Zipper` trait for more details.
-///
-/// To implement the trait, typically you would use one of the macros
-/// like `eq_zip!`, `struct_zip!`, or `enum_zip!`.
-pub trait Zip<I>: Debug
-where
-    I: Interner,
-{
-    /// Uses the zipper to walk through two values, ensuring that they match.
-    fn zip_with<Z: Zipper<I>>(
-        zipper: &mut Z,
-        variance: Variance,
-        a: &Self,
-        b: &Self,
-    ) -> Fallible<()>;
-}
-
-impl<'a, T: ?Sized + Zip<I>, I: Interner> Zip<I> for &'a T {
-    fn zip_with<Z: Zipper<I>>(
-        zipper: &mut Z,
-        variance: Variance,
-        a: &Self,
-        b: &Self,
-    ) -> Fallible<()> {
-        <T as Zip<I>>::zip_with(zipper, variance, a, b)
-    }
-}
-
-impl<I: Interner> Zip<I> for () {
-    fn zip_with<Z: Zipper<I>>(_: &mut Z, _: Variance, _: &Self, _: &Self) -> Fallible<()> {
-        Ok(())
-    }
-}
-
-impl<T: Zip<I>, I: Interner> Zip<I> for Vec<T> {
-    fn zip_with<Z: Zipper<I>>(
-        zipper: &mut Z,
-        variance: Variance,
-        a: &Self,
-        b: &Self,
-    ) -> Fallible<()> {
-        <[T] as Zip<I>>::zip_with(zipper, variance, a, b)
-    }
-}
-
-impl<T: Zip<I>, I: Interner> Zip<I> for [T] {
-    fn zip_with<Z: Zipper<I>>(
-        zipper: &mut Z,
-        variance: Variance,
-        a: &Self,
-        b: &Self,
-    ) -> Fallible<()> {
-        if a.len() != b.len() {
-            return Err(NoSolution);
-        }
-
-        for (a_elem, b_elem) in a.iter().zip(b) {
-            Zip::zip_with(zipper, variance, a_elem, b_elem)?;
-        }
-
-        Ok(())
-    }
-}
-
-impl<T: Zip<I>, I: Interner> Zip<I> for Arc<T> {
-    fn zip_with<Z: Zipper<I>>(
-        zipper: &mut Z,
-        variance: Variance,
-        a: &Self,
-        b: &Self,
-    ) -> Fallible<()> {
-        <T as Zip<I>>::zip_with(zipper, variance, a, b)
-    }
-}
-
-impl<T: Zip<I>, I: Interner> Zip<I> for Box<T> {
-    fn zip_with<Z: Zipper<I>>(
-        zipper: &mut Z,
-        variance: Variance,
-        a: &Self,
-        b: &Self,
-    ) -> Fallible<()> {
-        <T as Zip<I>>::zip_with(zipper, variance, a, b)
-    }
-}
-
-impl<T: Zip<I>, U: Zip<I>, I: Interner> Zip<I> for (T, U) {
-    fn zip_with<Z: Zipper<I>>(
-        zipper: &mut Z,
-        variance: Variance,
-        a: &Self,
-        b: &Self,
-    ) -> Fallible<()> {
-        Zip::zip_with(zipper, variance, &a.0, &b.0)?;
-        Zip::zip_with(zipper, variance, &a.1, &b.1)?;
-        Ok(())
-    }
-}
-
-impl<I: Interner> Zip<I> for Ty<I> {
-    fn zip_with<Z: Zipper<I>>(
-        zipper: &mut Z,
-        variance: Variance,
-        a: &Self,
-        b: &Self,
-    ) -> Fallible<()> {
-        zipper.zip_tys(variance, a, b)
-    }
-}
-
-impl<I: Interner> Zip<I> for Lifetime<I> {
-    fn zip_with<Z: Zipper<I>>(
-        zipper: &mut Z,
-        variance: Variance,
-        a: &Self,
-        b: &Self,
-    ) -> Fallible<()> {
-        zipper.zip_lifetimes(variance, a, b)
-    }
-}
-
-impl<I: Interner> Zip<I> for Const<I> {
-    fn zip_with<Z: Zipper<I>>(
-        zipper: &mut Z,
-        variance: Variance,
-        a: &Self,
-        b: &Self,
-    ) -> Fallible<()> {
-        zipper.zip_consts(variance, a, b)
-    }
-}
-impl<I: Interner, T> Zip<I> for Binders<T>
-where
-    T: Clone + HasInterner<Interner = I> + Zip<I> + TypeFoldable<I>,
-{
-    fn zip_with<Z: Zipper<I>>(
-        zipper: &mut Z,
-        variance: Variance,
-        a: &Self,
-        b: &Self,
-    ) -> Fallible<()> {
-        zipper.zip_binders(variance, a, b)
-    }
-}
-
-/// Generates a Zip impl that requires the two values be
-/// equal. Suitable for atomic, scalar values.
-macro_rules! eq_zip {
-    ($I:ident => $t:ty) => {
-        impl<$I: Interner> Zip<$I> for $t {
-            fn zip_with<Z: Zipper<$I>>(
-                _zipper: &mut Z,
-                _variance: Variance,
-                a: &Self,
-                b: &Self,
-            ) -> Fallible<()> {
-                if a != b {
-                    return Err(NoSolution);
-                }
-                Ok(())
-            }
-        }
-    };
-}
-
-eq_zip!(I => AdtId<I>);
-eq_zip!(I => TraitId<I>);
-eq_zip!(I => AssocTypeId<I>);
-eq_zip!(I => OpaqueTyId<I>);
-eq_zip!(I => GeneratorId<I>);
-eq_zip!(I => ForeignDefId<I>);
-eq_zip!(I => FnDefId<I>);
-eq_zip!(I => ClosureId<I>);
-eq_zip!(I => QuantifierKind);
-eq_zip!(I => PhantomData<I>);
-eq_zip!(I => PlaceholderIndex);
-eq_zip!(I => ClausePriority);
-eq_zip!(I => Mutability);
-eq_zip!(I => Scalar);
-
-impl<T: HasInterner<Interner = I> + Zip<I>, I: Interner> Zip<I> for InEnvironment<T> {
-    fn zip_with<Z: Zipper<I>>(
-        zipper: &mut Z,
-        variance: Variance,
-        a: &Self,
-        b: &Self,
-    ) -> Fallible<()> {
-        Zip::zip_with(zipper, variance, &a.environment, &b.environment)?;
-        Zip::zip_with(zipper, variance, &a.goal, &b.goal)?;
-        Ok(())
-    }
-}
-
-impl<I: Interner> Zip<I> for Environment<I> {
-    fn zip_with<Z: Zipper<I>>(
-        zipper: &mut Z,
-        variance: Variance,
-        a: &Self,
-        b: &Self,
-    ) -> Fallible<()> {
-        let interner = zipper.interner();
-        assert_eq!(a.clauses.len(interner), b.clauses.len(interner)); // or different numbers of clauses
-        Zip::zip_with(
-            zipper,
-            variance,
-            a.clauses.as_slice(interner),
-            b.clauses.as_slice(interner),
-        )?;
-        Ok(())
-    }
-}
-
-impl<I: Interner> Zip<I> for Goals<I> {
-    fn zip_with<Z: Zipper<I>>(
-        zipper: &mut Z,
-        variance: Variance,
-        a: &Self,
-        b: &Self,
-    ) -> Fallible<()> {
-        let interner = zipper.interner();
-        Zip::zip_with(zipper, variance, a.as_slice(interner), b.as_slice(interner))?;
-        Ok(())
-    }
-}
-
-impl<I: Interner> Zip<I> for ProgramClauses<I> {
-    fn zip_with<Z: Zipper<I>>(
-        zipper: &mut Z,
-        variance: Variance,
-        a: &Self,
-        b: &Self,
-    ) -> Fallible<()> {
-        let interner = zipper.interner();
-        Zip::zip_with(zipper, variance, a.as_slice(interner), b.as_slice(interner))?;
-        Ok(())
-    }
-}
-
-impl<I: Interner> Zip<I> for Constraints<I> {
-    fn zip_with<Z: Zipper<I>>(
-        zipper: &mut Z,
-        variance: Variance,
-        a: &Self,
-        b: &Self,
-    ) -> Fallible<()> {
-        let interner = zipper.interner();
-        Zip::zip_with(zipper, variance, a.as_slice(interner), b.as_slice(interner))?;
-        Ok(())
-    }
-}
-
-impl<I: Interner> Zip<I> for QuantifiedWhereClauses<I> {
-    fn zip_with<Z: Zipper<I>>(
-        zipper: &mut Z,
-        variance: Variance,
-        a: &Self,
-        b: &Self,
-    ) -> Fallible<()> {
-        let interner = zipper.interner();
-        Zip::zip_with(zipper, variance, a.as_slice(interner), b.as_slice(interner))?;
-        Ok(())
-    }
-}
-
-// Annoyingly, Goal cannot use `enum_zip` because some variants have
-// two parameters, and I'm too lazy to make the macro account for the
-// relevant name mangling.
-impl<I: Interner> Zip<I> for Goal<I> {
-    fn zip_with<Z: Zipper<I>>(
-        zipper: &mut Z,
-        variance: Variance,
-        a: &Self,
-        b: &Self,
-    ) -> Fallible<()> {
-        let interner = zipper.interner();
-        Zip::zip_with(zipper, variance, a.data(interner), b.data(interner))
-    }
-}
-
-// I'm too lazy to make `enum_zip` support type parameters.
-impl<I: Interner> Zip<I> for VariableKind<I> {
-    fn zip_with<Z: Zipper<I>>(
-        zipper: &mut Z,
-        variance: Variance,
-        a: &Self,
-        b: &Self,
-    ) -> Fallible<()> {
-        match (a, b) {
-            (VariableKind::Ty(a), VariableKind::Ty(b)) if a == b => Ok(()),
-            (VariableKind::Lifetime, VariableKind::Lifetime) => Ok(()),
-            (VariableKind::Const(ty_a), VariableKind::Const(ty_b)) => {
-                Zip::zip_with(zipper, variance, ty_a, ty_b)
-            }
-            (VariableKind::Ty(_), _)
-            | (VariableKind::Lifetime, _)
-            | (VariableKind::Const(_), _) => panic!("zipping things of mixed kind"),
-        }
-    }
-}
-
-impl<I: Interner> Zip<I> for GenericArg<I> {
-    fn zip_with<Z: Zipper<I>>(
-        zipper: &mut Z,
-        variance: Variance,
-        a: &Self,
-        b: &Self,
-    ) -> Fallible<()> {
-        let interner = zipper.interner();
-        Zip::zip_with(zipper, variance, a.data(interner), b.data(interner))
-    }
-}
-
-impl<I: Interner> Zip<I> for ProgramClause<I> {
-    fn zip_with<Z: Zipper<I>>(
-        zipper: &mut Z,
-        variance: Variance,
-        a: &Self,
-        b: &Self,
-    ) -> Fallible<()> {
-        let interner = zipper.interner();
-        Zip::zip_with(zipper, variance, a.data(interner), b.data(interner))
-    }
-}
-
-impl<I: Interner> Zip<I> for TraitRef<I> {
-    fn zip_with<Z: Zipper<I>>(
-        zipper: &mut Z,
-        variance: Variance,
-        a: &Self,
-        b: &Self,
-    ) -> Fallible<()> {
-        let interner = zipper.interner();
-        Zip::zip_with(zipper, variance, &a.trait_id, &b.trait_id)?;
-        zipper.zip_substs(
-            variance,
-            None,
-            a.substitution.as_slice(interner),
-            b.substitution.as_slice(interner),
-        )
-    }
-}
-
-impl<I: Interner> Zip<I> for ProjectionTy<I> {
-    fn zip_with<Z: Zipper<I>>(
-        zipper: &mut Z,
-        variance: Variance,
-        a: &Self,
-        b: &Self,
-    ) -> Fallible<()> {
-        let interner = zipper.interner();
-        Zip::zip_with(zipper, variance, &a.associated_ty_id, &b.associated_ty_id)?;
-        zipper.zip_substs(
-            variance,
-            None,
-            a.substitution.as_slice(interner),
-            b.substitution.as_slice(interner),
-        )
-    }
-}
-
-impl<I: Interner> Zip<I> for OpaqueTy<I> {
-    fn zip_with<Z: Zipper<I>>(
-        zipper: &mut Z,
-        variance: Variance,
-        a: &Self,
-        b: &Self,
-    ) -> Fallible<()> {
-        let interner = zipper.interner();
-        Zip::zip_with(zipper, variance, &a.opaque_ty_id, &b.opaque_ty_id)?;
-        zipper.zip_substs(
-            variance,
-            None,
-            a.substitution.as_slice(interner),
-            b.substitution.as_slice(interner),
-        )
-    }
-}
-
-impl<I: Interner> Zip<I> for DynTy<I> {
-    fn zip_with<Z: Zipper<I>>(
-        zipper: &mut Z,
-        variance: Variance,
-        a: &Self,
-        b: &Self,
-    ) -> Fallible<()> {
-        Zip::zip_with(
-            zipper,
-            variance.xform(Variance::Invariant),
-            &a.bounds,
-            &b.bounds,
-        )?;
-        Zip::zip_with(
-            zipper,
-            variance.xform(Variance::Contravariant),
-            &a.lifetime,
-            &b.lifetime,
-        )?;
-        Ok(())
-    }
-}
-
-impl<I: Interner> Zip<I> for FnSubst<I> {
-    fn zip_with<Z: Zipper<I>>(
-        zipper: &mut Z,
-        variance: Variance,
-        a: &Self,
-        b: &Self,
-    ) -> Fallible<()> {
-        let interner = zipper.interner();
-        // Parameters
-        Zip::zip_with(
-            zipper,
-            variance.xform(Variance::Contravariant),
-            &a.0.as_slice(interner)[..a.0.len(interner) - 1],
-            &b.0.as_slice(interner)[..b.0.len(interner) - 1],
-        )?;
-        // Return type
-        Zip::zip_with(
-            zipper,
-            variance,
-            a.0.iter(interner).last().unwrap(),
-            b.0.iter(interner).last().unwrap(),
-        )?;
-        Ok(())
-    }
-}