Merging upstream version 1.72.1+dfsg1.

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

1 files changed, 0 insertions, 1241 deletions

diff --git a/compiler/rustc_traits/src/chalk/lowering.rs b/compiler/rustc_traits/src/chalk/lowering.rs
deleted file mode 100644
index e447ab94f..000000000
--- a/compiler/rustc_traits/src/chalk/lowering.rs
+++ /dev/null
@@ -1,1241 +0,0 @@
-//! Contains the logic to lower rustc types into Chalk types
-//!
-//! In many cases there is a 1:1 relationship between a rustc type and a Chalk type.
-//! For example, a `SubstsRef` maps almost directly to a `Substitution`. In some
-//! other cases, such as `Param`s, there is no Chalk type, so we have to handle
-//! accordingly.
-//!
-//! ## `Ty` lowering
-//! Much of the `Ty` lowering is 1:1 with Chalk. (Or will be eventually). A
-//! helpful table for what types lower to what can be found in the
-//! [Chalk book](https://rust-lang.github.io/chalk/book/types/rust_types.html).
-//! The most notable difference lies with `Param`s. To convert from rustc to
-//! Chalk, we eagerly and deeply convert `Param`s to placeholders (in goals) or
-//! bound variables (for clause generation through functions in `db`).
-//!
-//! ## `Region` lowering
-//! Regions are handled in rustc and Chalk is quite differently. In rustc, there
-//! is a difference between "early bound" and "late bound" regions, where only
-//! the late bound regions have a `DebruijnIndex`. Moreover, in Chalk all
-//! regions (Lifetimes) have an associated index. In rustc, only `BrAnon`s have
-//! an index, whereas `BrNamed` don't. In order to lower regions to Chalk, we
-//! convert all regions into `BrAnon` late-bound regions.
-//!
-//! ## `Const` lowering
-//! Chalk doesn't handle consts currently, so consts are currently lowered to
-//! an empty tuple.
-//!
-//! ## Bound variable collection
-//! Another difference between rustc and Chalk lies in the handling of binders.
-//! Chalk requires that we store the bound parameter kinds, whereas rustc does
-//! not. To lower anything wrapped in a `Binder`, we first deeply find any bound
-//! variables from the current `Binder`.
-
-use rustc_ast::ast;
-use rustc_middle::traits::{ChalkEnvironmentAndGoal, ChalkRustInterner as RustInterner};
-use rustc_middle::ty::subst::{GenericArg, GenericArgKind, SubstsRef};
-use rustc_middle::ty::{
-    self, Binder, Region, Ty, TyCtxt, TypeFoldable, TypeFolder, TypeSuperFoldable,
-    TypeSuperVisitable, TypeVisitable, TypeVisitor,
-};
-use rustc_span::def_id::DefId;
-
-use chalk_ir::{FnSig, ForeignDefId};
-use rustc_hir::Unsafety;
-use std::collections::btree_map::{BTreeMap, Entry};
-use std::ops::ControlFlow;
-
-/// Essentially an `Into` with a `&RustInterner` parameter
-pub(crate) trait LowerInto<'tcx, T> {
-    /// Lower a rustc construct (e.g., `ty::TraitPredicate`) to a chalk type, consuming `self`.
-    fn lower_into(self, interner: RustInterner<'tcx>) -> T;
-}
-
-impl<'tcx> LowerInto<'tcx, chalk_ir::Substitution<RustInterner<'tcx>>> for SubstsRef<'tcx> {
-    fn lower_into(
-        self,
-        interner: RustInterner<'tcx>,
-    ) -> chalk_ir::Substitution<RustInterner<'tcx>> {
-        chalk_ir::Substitution::from_iter(interner, self.iter().map(|s| s.lower_into(interner)))
-    }
-}
-
-impl<'tcx> LowerInto<'tcx, chalk_ir::Substitution<RustInterner<'tcx>>>
-    for &'tcx ty::List<Ty<'tcx>>
-{
-    fn lower_into(
-        self,
-        interner: RustInterner<'tcx>,
-    ) -> chalk_ir::Substitution<RustInterner<'tcx>> {
-        chalk_ir::Substitution::from_iter(
-            interner,
-            self.iter().map(|ty| GenericArg::from(ty).lower_into(interner)),
-        )
-    }
-}
-
-impl<'tcx> LowerInto<'tcx, SubstsRef<'tcx>> for &chalk_ir::Substitution<RustInterner<'tcx>> {
-    fn lower_into(self, interner: RustInterner<'tcx>) -> SubstsRef<'tcx> {
-        interner
-            .tcx
-            .mk_substs_from_iter(self.iter(interner).map(|subst| subst.lower_into(interner)))
-    }
-}
-
-impl<'tcx> LowerInto<'tcx, chalk_ir::InEnvironment<chalk_ir::Goal<RustInterner<'tcx>>>>
-    for ChalkEnvironmentAndGoal<'tcx>
-{
-    fn lower_into(
-        self,
-        interner: RustInterner<'tcx>,
-    ) -> chalk_ir::InEnvironment<chalk_ir::Goal<RustInterner<'tcx>>> {
-        let clauses = self.environment.into_iter().map(|predicate| {
-            let (predicate, binders, _named_regions) =
-                collect_bound_vars(interner, interner.tcx, predicate.kind());
-            let consequence = match predicate {
-                ty::PredicateKind::TypeWellFormedFromEnv(ty) => {
-                    chalk_ir::DomainGoal::FromEnv(chalk_ir::FromEnv::Ty(ty.lower_into(interner)))
-                }
-                ty::PredicateKind::Clause(ty::Clause::Trait(predicate)) => {
-                    chalk_ir::DomainGoal::FromEnv(chalk_ir::FromEnv::Trait(
-                        predicate.trait_ref.lower_into(interner),
-                    ))
-                }
-                ty::PredicateKind::Clause(ty::Clause::RegionOutlives(predicate)) => {
-                    chalk_ir::DomainGoal::Holds(chalk_ir::WhereClause::LifetimeOutlives(
-                        chalk_ir::LifetimeOutlives {
-                            a: predicate.0.lower_into(interner),
-                            b: predicate.1.lower_into(interner),
-                        },
-                    ))
-                }
-                ty::PredicateKind::Clause(ty::Clause::TypeOutlives(predicate)) => {
-                    chalk_ir::DomainGoal::Holds(chalk_ir::WhereClause::TypeOutlives(
-                        chalk_ir::TypeOutlives {
-                            ty: predicate.0.lower_into(interner),
-                            lifetime: predicate.1.lower_into(interner),
-                        },
-                    ))
-                }
-                ty::PredicateKind::Clause(ty::Clause::Projection(predicate)) => {
-                    chalk_ir::DomainGoal::Holds(chalk_ir::WhereClause::AliasEq(
-                        predicate.lower_into(interner),
-                    ))
-                }
-                ty::PredicateKind::WellFormed(arg) => match arg.unpack() {
-                    ty::GenericArgKind::Type(ty) => chalk_ir::DomainGoal::WellFormed(
-                        chalk_ir::WellFormed::Ty(ty.lower_into(interner)),
-                    ),
-                    // FIXME(chalk): we need to change `WellFormed` in Chalk to take a `GenericArg`
-                    _ => chalk_ir::DomainGoal::WellFormed(chalk_ir::WellFormed::Ty(
-                        interner.tcx.types.unit.lower_into(interner),
-                    )),
-                },
-                ty::PredicateKind::ObjectSafe(..)
-                | ty::PredicateKind::Clause(ty::Clause::ConstArgHasType(..))
-                | ty::PredicateKind::AliasRelate(..)
-                | ty::PredicateKind::ClosureKind(..)
-                | ty::PredicateKind::Subtype(..)
-                | ty::PredicateKind::Coerce(..)
-                | ty::PredicateKind::ConstEvaluatable(..)
-                | ty::PredicateKind::Ambiguous
-                | ty::PredicateKind::ConstEquate(..) => bug!("unexpected predicate {}", predicate),
-            };
-            let value = chalk_ir::ProgramClauseImplication {
-                consequence,
-                conditions: chalk_ir::Goals::empty(interner),
-                priority: chalk_ir::ClausePriority::High,
-                constraints: chalk_ir::Constraints::empty(interner),
-            };
-            chalk_ir::ProgramClauseData(chalk_ir::Binders::new(binders, value)).intern(interner)
-        });
-
-        let goal: chalk_ir::GoalData<RustInterner<'tcx>> = self.goal.lower_into(interner);
-        chalk_ir::InEnvironment {
-            environment: chalk_ir::Environment {
-                clauses: chalk_ir::ProgramClauses::from_iter(interner, clauses),
-            },
-            goal: goal.intern(interner),
-        }
-    }
-}
-
-impl<'tcx> LowerInto<'tcx, chalk_ir::GoalData<RustInterner<'tcx>>> for ty::Predicate<'tcx> {
-    fn lower_into(self, interner: RustInterner<'tcx>) -> chalk_ir::GoalData<RustInterner<'tcx>> {
-        let (predicate, binders, _named_regions) =
-            collect_bound_vars(interner, interner.tcx, self.kind());
-
-        let value = match predicate {
-            ty::PredicateKind::Clause(ty::Clause::Trait(predicate)) => {
-                chalk_ir::GoalData::DomainGoal(chalk_ir::DomainGoal::Holds(
-                    chalk_ir::WhereClause::Implemented(predicate.trait_ref.lower_into(interner)),
-                ))
-            }
-            ty::PredicateKind::Clause(ty::Clause::RegionOutlives(predicate)) => {
-                chalk_ir::GoalData::DomainGoal(chalk_ir::DomainGoal::Holds(
-                    chalk_ir::WhereClause::LifetimeOutlives(chalk_ir::LifetimeOutlives {
-                        a: predicate.0.lower_into(interner),
-                        b: predicate.1.lower_into(interner),
-                    }),
-                ))
-            }
-            ty::PredicateKind::Clause(ty::Clause::TypeOutlives(predicate)) => {
-                chalk_ir::GoalData::DomainGoal(chalk_ir::DomainGoal::Holds(
-                    chalk_ir::WhereClause::TypeOutlives(chalk_ir::TypeOutlives {
-                        ty: predicate.0.lower_into(interner),
-                        lifetime: predicate.1.lower_into(interner),
-                    }),
-                ))
-            }
-            ty::PredicateKind::Clause(ty::Clause::Projection(predicate)) => {
-                chalk_ir::GoalData::DomainGoal(chalk_ir::DomainGoal::Holds(
-                    chalk_ir::WhereClause::AliasEq(predicate.lower_into(interner)),
-                ))
-            }
-            ty::PredicateKind::WellFormed(arg) => match arg.unpack() {
-                GenericArgKind::Type(ty) => match ty.kind() {
-                    // FIXME(chalk): In Chalk, a placeholder is WellFormed if it
-                    // `FromEnv`. However, when we "lower" Params, we don't update
-                    // the environment.
-                    ty::Placeholder(..) => {
-                        chalk_ir::GoalData::All(chalk_ir::Goals::empty(interner))
-                    }
-
-                    _ => chalk_ir::GoalData::DomainGoal(chalk_ir::DomainGoal::WellFormed(
-                        chalk_ir::WellFormed::Ty(ty.lower_into(interner)),
-                    )),
-                },
-                // FIXME(chalk): handle well formed consts
-                GenericArgKind::Const(..) => {
-                    chalk_ir::GoalData::All(chalk_ir::Goals::empty(interner))
-                }
-                GenericArgKind::Lifetime(lt) => bug!("unexpected well formed predicate: {:?}", lt),
-            },
-
-            ty::PredicateKind::ObjectSafe(t) => chalk_ir::GoalData::DomainGoal(
-                chalk_ir::DomainGoal::ObjectSafe(chalk_ir::TraitId(t)),
-            ),
-
-            ty::PredicateKind::Subtype(ty::SubtypePredicate { a, b, a_is_expected: _ }) => {
-                chalk_ir::GoalData::SubtypeGoal(chalk_ir::SubtypeGoal {
-                    a: a.lower_into(interner),
-                    b: b.lower_into(interner),
-                })
-            }
-
-            // FIXME(chalk): other predicates
-            //
-            // We can defer this, but ultimately we'll want to express
-            // some of these in terms of chalk operations.
-            ty::PredicateKind::ClosureKind(..)
-            | ty::PredicateKind::Clause(ty::Clause::ConstArgHasType(..))
-            | ty::PredicateKind::AliasRelate(..)
-            | ty::PredicateKind::Coerce(..)
-            | ty::PredicateKind::ConstEvaluatable(..)
-            | ty::PredicateKind::Ambiguous
-            | ty::PredicateKind::ConstEquate(..) => {
-                chalk_ir::GoalData::All(chalk_ir::Goals::empty(interner))
-            }
-            ty::PredicateKind::TypeWellFormedFromEnv(ty) => chalk_ir::GoalData::DomainGoal(
-                chalk_ir::DomainGoal::FromEnv(chalk_ir::FromEnv::Ty(ty.lower_into(interner))),
-            ),
-        };
-
-        chalk_ir::GoalData::Quantified(
-            chalk_ir::QuantifierKind::ForAll,
-            chalk_ir::Binders::new(binders, value.intern(interner)),
-        )
-    }
-}
-
-impl<'tcx> LowerInto<'tcx, chalk_ir::TraitRef<RustInterner<'tcx>>>
-    for rustc_middle::ty::TraitRef<'tcx>
-{
-    fn lower_into(self, interner: RustInterner<'tcx>) -> chalk_ir::TraitRef<RustInterner<'tcx>> {
-        chalk_ir::TraitRef {
-            trait_id: chalk_ir::TraitId(self.def_id),
-            substitution: self.substs.lower_into(interner),
-        }
-    }
-}
-
-impl<'tcx> LowerInto<'tcx, chalk_ir::AliasEq<RustInterner<'tcx>>>
-    for rustc_middle::ty::ProjectionPredicate<'tcx>
-{
-    fn lower_into(self, interner: RustInterner<'tcx>) -> chalk_ir::AliasEq<RustInterner<'tcx>> {
-        // FIXME(associated_const_equality): teach chalk about terms for alias eq.
-        chalk_ir::AliasEq {
-            ty: self.term.ty().unwrap().lower_into(interner),
-            alias: chalk_ir::AliasTy::Projection(chalk_ir::ProjectionTy {
-                associated_ty_id: chalk_ir::AssocTypeId(self.projection_ty.def_id),
-                substitution: self.projection_ty.substs.lower_into(interner),
-            }),
-        }
-    }
-}
-
-/*
-// FIXME(...): Where do I add this to Chalk? I can't find it in the rustc repo anywhere.
-impl<'tcx> LowerInto<'tcx, chalk_ir::Term<RustInterner<'tcx>>> for rustc_middle::ty::Term<'tcx> {
-  fn lower_into(self, interner: RustInterner<'tcx>) -> chalk_ir::Term<RustInterner<'tcx>> {
-    match self {
-      ty::Term::Ty(ty) => ty.lower_into(interner).into(),
-      ty::Term::Const(c) => c.lower_into(interner).into(),
-    }
-  }
-}
-*/
-
-impl<'tcx> LowerInto<'tcx, chalk_ir::Ty<RustInterner<'tcx>>> for Ty<'tcx> {
-    fn lower_into(self, interner: RustInterner<'tcx>) -> chalk_ir::Ty<RustInterner<'tcx>> {
-        let int = |i| chalk_ir::TyKind::Scalar(chalk_ir::Scalar::Int(i));
-        let uint = |i| chalk_ir::TyKind::Scalar(chalk_ir::Scalar::Uint(i));
-        let float = |f| chalk_ir::TyKind::Scalar(chalk_ir::Scalar::Float(f));
-
-        match *self.kind() {
-            ty::Bool => chalk_ir::TyKind::Scalar(chalk_ir::Scalar::Bool),
-            ty::Char => chalk_ir::TyKind::Scalar(chalk_ir::Scalar::Char),
-            ty::Int(ty) => match ty {
-                ty::IntTy::Isize => int(chalk_ir::IntTy::Isize),
-                ty::IntTy::I8 => int(chalk_ir::IntTy::I8),
-                ty::IntTy::I16 => int(chalk_ir::IntTy::I16),
-                ty::IntTy::I32 => int(chalk_ir::IntTy::I32),
-                ty::IntTy::I64 => int(chalk_ir::IntTy::I64),
-                ty::IntTy::I128 => int(chalk_ir::IntTy::I128),
-            },
-            ty::Uint(ty) => match ty {
-                ty::UintTy::Usize => uint(chalk_ir::UintTy::Usize),
-                ty::UintTy::U8 => uint(chalk_ir::UintTy::U8),
-                ty::UintTy::U16 => uint(chalk_ir::UintTy::U16),
-                ty::UintTy::U32 => uint(chalk_ir::UintTy::U32),
-                ty::UintTy::U64 => uint(chalk_ir::UintTy::U64),
-                ty::UintTy::U128 => uint(chalk_ir::UintTy::U128),
-            },
-            ty::Float(ty) => match ty {
-                ty::FloatTy::F32 => float(chalk_ir::FloatTy::F32),
-                ty::FloatTy::F64 => float(chalk_ir::FloatTy::F64),
-            },
-            ty::Adt(def, substs) => {
-                chalk_ir::TyKind::Adt(chalk_ir::AdtId(def), substs.lower_into(interner))
-            }
-            ty::Foreign(def_id) => chalk_ir::TyKind::Foreign(ForeignDefId(def_id)),
-            ty::Str => chalk_ir::TyKind::Str,
-            ty::Array(ty, len) => {
-                chalk_ir::TyKind::Array(ty.lower_into(interner), len.lower_into(interner))
-            }
-            ty::Slice(ty) => chalk_ir::TyKind::Slice(ty.lower_into(interner)),
-
-            ty::RawPtr(ptr) => {
-                chalk_ir::TyKind::Raw(ptr.mutbl.lower_into(interner), ptr.ty.lower_into(interner))
-            }
-            ty::Ref(region, ty, mutability) => chalk_ir::TyKind::Ref(
-                mutability.lower_into(interner),
-                region.lower_into(interner),
-                ty.lower_into(interner),
-            ),
-            ty::FnDef(def_id, substs) => {
-                chalk_ir::TyKind::FnDef(chalk_ir::FnDefId(def_id), substs.lower_into(interner))
-            }
-            ty::FnPtr(sig) => {
-                let (inputs_and_outputs, binders, _named_regions) =
-                    collect_bound_vars(interner, interner.tcx, sig.inputs_and_output());
-                chalk_ir::TyKind::Function(chalk_ir::FnPointer {
-                    num_binders: binders.len(interner),
-                    sig: sig.lower_into(interner),
-                    substitution: chalk_ir::FnSubst(chalk_ir::Substitution::from_iter(
-                        interner,
-                        inputs_and_outputs.iter().map(|ty| {
-                            chalk_ir::GenericArgData::Ty(ty.lower_into(interner)).intern(interner)
-                        }),
-                    )),
-                })
-            }
-            // FIXME(dyn-star): handle the dynamic kind (dyn or dyn*)
-            ty::Dynamic(predicates, region, _kind) => chalk_ir::TyKind::Dyn(chalk_ir::DynTy {
-                bounds: predicates.lower_into(interner),
-                lifetime: region.lower_into(interner),
-            }),
-            ty::Closure(def_id, substs) => {
-                chalk_ir::TyKind::Closure(chalk_ir::ClosureId(def_id), substs.lower_into(interner))
-            }
-            ty::Generator(def_id, substs, _) => chalk_ir::TyKind::Generator(
-                chalk_ir::GeneratorId(def_id),
-                substs.lower_into(interner),
-            ),
-            ty::GeneratorWitness(_) => unimplemented!(),
-            ty::GeneratorWitnessMIR(..) => unimplemented!(),
-            ty::Never => chalk_ir::TyKind::Never,
-            ty::Tuple(types) => chalk_ir::TyKind::Tuple(types.len(), types.lower_into(interner)),
-            ty::Alias(ty::Projection, ty::AliasTy { def_id, substs, .. }) => {
-                chalk_ir::TyKind::Alias(chalk_ir::AliasTy::Projection(chalk_ir::ProjectionTy {
-                    associated_ty_id: chalk_ir::AssocTypeId(def_id),
-                    substitution: substs.lower_into(interner),
-                }))
-            }
-            ty::Alias(ty::Inherent, _) => unimplemented!(),
-            ty::Alias(ty::Opaque, ty::AliasTy { def_id, substs, .. }) => {
-                chalk_ir::TyKind::Alias(chalk_ir::AliasTy::Opaque(chalk_ir::OpaqueTy {
-                    opaque_ty_id: chalk_ir::OpaqueTyId(def_id),
-                    substitution: substs.lower_into(interner),
-                }))
-            }
-            // This should have been done eagerly prior to this, and all Params
-            // should have been substituted to placeholders
-            ty::Param(_) => panic!("Lowering Param when not expected."),
-            ty::Bound(db, bound) => chalk_ir::TyKind::BoundVar(chalk_ir::BoundVar::new(
-                chalk_ir::DebruijnIndex::new(db.as_u32()),
-                bound.var.index(),
-            )),
-            ty::Placeholder(_placeholder) => {
-                chalk_ir::TyKind::Placeholder(chalk_ir::PlaceholderIndex {
-                    ui: chalk_ir::UniverseIndex { counter: _placeholder.universe.as_usize() },
-                    idx: _placeholder.bound.var.as_usize(),
-                })
-            }
-            ty::Infer(_infer) => unimplemented!(),
-            ty::Error(_) => chalk_ir::TyKind::Error,
-        }
-        .intern(interner)
-    }
-}
-
-impl<'tcx> LowerInto<'tcx, Ty<'tcx>> for &chalk_ir::Ty<RustInterner<'tcx>> {
-    fn lower_into(self, interner: RustInterner<'tcx>) -> Ty<'tcx> {
-        use chalk_ir::TyKind;
-
-        let kind = match self.kind(interner) {
-            TyKind::Adt(struct_id, substitution) => {
-                ty::Adt(struct_id.0, substitution.lower_into(interner))
-            }
-            TyKind::Scalar(scalar) => match scalar {
-                chalk_ir::Scalar::Bool => ty::Bool,
-                chalk_ir::Scalar::Char => ty::Char,
-                chalk_ir::Scalar::Int(int_ty) => match int_ty {
-                    chalk_ir::IntTy::Isize => ty::Int(ty::IntTy::Isize),
-                    chalk_ir::IntTy::I8 => ty::Int(ty::IntTy::I8),
-                    chalk_ir::IntTy::I16 => ty::Int(ty::IntTy::I16),
-                    chalk_ir::IntTy::I32 => ty::Int(ty::IntTy::I32),
-                    chalk_ir::IntTy::I64 => ty::Int(ty::IntTy::I64),
-                    chalk_ir::IntTy::I128 => ty::Int(ty::IntTy::I128),
-                },
-                chalk_ir::Scalar::Uint(int_ty) => match int_ty {
-                    chalk_ir::UintTy::Usize => ty::Uint(ty::UintTy::Usize),
-                    chalk_ir::UintTy::U8 => ty::Uint(ty::UintTy::U8),
-                    chalk_ir::UintTy::U16 => ty::Uint(ty::UintTy::U16),
-                    chalk_ir::UintTy::U32 => ty::Uint(ty::UintTy::U32),
-                    chalk_ir::UintTy::U64 => ty::Uint(ty::UintTy::U64),
-                    chalk_ir::UintTy::U128 => ty::Uint(ty::UintTy::U128),
-                },
-                chalk_ir::Scalar::Float(float_ty) => match float_ty {
-                    chalk_ir::FloatTy::F32 => ty::Float(ty::FloatTy::F32),
-                    chalk_ir::FloatTy::F64 => ty::Float(ty::FloatTy::F64),
-                },
-            },
-            TyKind::Array(ty, c) => {
-                let ty = ty.lower_into(interner);
-                let c = c.lower_into(interner);
-                ty::Array(ty, c)
-            }
-            TyKind::FnDef(id, substitution) => ty::FnDef(id.0, substitution.lower_into(interner)),
-            TyKind::Closure(closure, substitution) => {
-                ty::Closure(closure.0, substitution.lower_into(interner))
-            }
-            TyKind::Generator(generator, substitution) => ty::Generator(
-                generator.0,
-                substitution.lower_into(interner),
-                ast::Movability::Static,
-            ),
-            TyKind::GeneratorWitness(..) => unimplemented!(),
-            TyKind::Never => ty::Never,
-            TyKind::Tuple(_len, substitution) => {
-                ty::Tuple(substitution.lower_into(interner).into_type_list(interner.tcx))
-            }
-            TyKind::Slice(ty) => ty::Slice(ty.lower_into(interner)),
-            TyKind::Raw(mutbl, ty) => ty::RawPtr(ty::TypeAndMut {
-                ty: ty.lower_into(interner),
-                mutbl: mutbl.lower_into(interner),
-            }),
-            TyKind::Ref(mutbl, lifetime, ty) => ty::Ref(
-                lifetime.lower_into(interner),
-                ty.lower_into(interner),
-                mutbl.lower_into(interner),
-            ),
-            TyKind::Str => ty::Str,
-            TyKind::OpaqueType(opaque_ty, substitution) => ty::Alias(
-                ty::Opaque,
-                interner.tcx.mk_alias_ty(opaque_ty.0, substitution.lower_into(interner)),
-            ),
-            TyKind::AssociatedType(assoc_ty, substitution) => ty::Alias(
-                ty::Projection,
-                interner.tcx.mk_alias_ty(assoc_ty.0, substitution.lower_into(interner)),
-            ),
-            TyKind::Foreign(def_id) => ty::Foreign(def_id.0),
-            TyKind::Error => return interner.tcx.ty_error_misc(),
-            TyKind::Alias(alias_ty) => match alias_ty {
-                chalk_ir::AliasTy::Projection(projection) => ty::Alias(
-                    ty::Projection,
-                    interner.tcx.mk_alias_ty(
-                        projection.associated_ty_id.0,
-                        projection.substitution.lower_into(interner),
-                    ),
-                ),
-                chalk_ir::AliasTy::Opaque(opaque) => ty::Alias(
-                    ty::Opaque,
-                    interner.tcx.mk_alias_ty(
-                        opaque.opaque_ty_id.0,
-                        opaque.substitution.lower_into(interner),
-                    ),
-                ),
-            },
-            TyKind::Function(_quantified_ty) => unimplemented!(),
-            TyKind::BoundVar(bound) => ty::Bound(
-                ty::DebruijnIndex::from_usize(bound.debruijn.depth() as usize),
-                ty::BoundTy {
-                    var: ty::BoundVar::from_usize(bound.index),
-                    kind: ty::BoundTyKind::Anon,
-                },
-            ),
-            TyKind::Placeholder(placeholder) => ty::Placeholder(ty::Placeholder {
-                universe: ty::UniverseIndex::from_usize(placeholder.ui.counter),
-                bound: ty::BoundTy {
-                    var: ty::BoundVar::from_usize(placeholder.idx),
-                    kind: ty::BoundTyKind::Anon,
-                },
-            }),
-            TyKind::InferenceVar(_, _) => unimplemented!(),
-            TyKind::Dyn(_) => unimplemented!(),
-        };
-        interner.tcx.mk_ty_from_kind(kind)
-    }
-}
-
-impl<'tcx> LowerInto<'tcx, chalk_ir::Lifetime<RustInterner<'tcx>>> for Region<'tcx> {
-    fn lower_into(self, interner: RustInterner<'tcx>) -> chalk_ir::Lifetime<RustInterner<'tcx>> {
-        match *self {
-            ty::ReEarlyBound(_) => {
-                panic!("Should have already been substituted.");
-            }
-            ty::ReError(_) => {
-                panic!("Error lifetime should not have already been lowered.");
-            }
-            ty::ReLateBound(db, br) => chalk_ir::LifetimeData::BoundVar(chalk_ir::BoundVar::new(
-                chalk_ir::DebruijnIndex::new(db.as_u32()),
-                br.var.as_usize(),
-            ))
-            .intern(interner),
-            ty::ReFree(_) => unimplemented!(),
-            ty::ReStatic => chalk_ir::LifetimeData::Static.intern(interner),
-            ty::ReVar(_) => unimplemented!(),
-            ty::RePlaceholder(placeholder_region) => {
-                chalk_ir::LifetimeData::Placeholder(chalk_ir::PlaceholderIndex {
-                    ui: chalk_ir::UniverseIndex { counter: placeholder_region.universe.index() },
-                    idx: 0, // FIXME: This `idx: 0` is sus.
-                })
-                .intern(interner)
-            }
-            ty::ReErased => chalk_ir::LifetimeData::Erased.intern(interner),
-        }
-    }
-}
-
-impl<'tcx> LowerInto<'tcx, Region<'tcx>> for &chalk_ir::Lifetime<RustInterner<'tcx>> {
-    fn lower_into(self, interner: RustInterner<'tcx>) -> Region<'tcx> {
-        let tcx = interner.tcx;
-        match self.data(interner) {
-            chalk_ir::LifetimeData::BoundVar(var) => tcx.mk_re_late_bound(
-                ty::DebruijnIndex::from_u32(var.debruijn.depth()),
-                ty::BoundRegion {
-                    var: ty::BoundVar::from_usize(var.index),
-                    kind: ty::BrAnon(None),
-                },
-            ),
-            chalk_ir::LifetimeData::InferenceVar(_var) => unimplemented!(),
-            chalk_ir::LifetimeData::Placeholder(p) => tcx.mk_re_placeholder(ty::Placeholder {
-                universe: ty::UniverseIndex::from_usize(p.ui.counter),
-                bound: ty::BoundRegion {
-                    var: ty::BoundVar::from_usize(p.idx),
-                    kind: ty::BoundRegionKind::BrAnon(None),
-                },
-            }),
-            chalk_ir::LifetimeData::Static => tcx.lifetimes.re_static,
-            chalk_ir::LifetimeData::Erased => tcx.lifetimes.re_erased,
-            chalk_ir::LifetimeData::Phantom(void, _) => match *void {},
-        }
-    }
-}
-
-impl<'tcx> LowerInto<'tcx, chalk_ir::Const<RustInterner<'tcx>>> for ty::Const<'tcx> {
-    fn lower_into(self, interner: RustInterner<'tcx>) -> chalk_ir::Const<RustInterner<'tcx>> {
-        let ty = self.ty().lower_into(interner);
-        let value = match self.kind() {
-            ty::ConstKind::Value(val) => {
-                chalk_ir::ConstValue::Concrete(chalk_ir::ConcreteConst { interned: val })
-            }
-            ty::ConstKind::Bound(db, bound) => chalk_ir::ConstValue::BoundVar(
-                chalk_ir::BoundVar::new(chalk_ir::DebruijnIndex::new(db.as_u32()), bound.index()),
-            ),
-            _ => unimplemented!("Const not implemented. {:?}", self),
-        };
-        chalk_ir::ConstData { ty, value }.intern(interner)
-    }
-}
-
-impl<'tcx> LowerInto<'tcx, ty::Const<'tcx>> for &chalk_ir::Const<RustInterner<'tcx>> {
-    fn lower_into(self, interner: RustInterner<'tcx>) -> ty::Const<'tcx> {
-        let data = self.data(interner);
-        let ty = data.ty.lower_into(interner);
-        let kind = match data.value {
-            chalk_ir::ConstValue::BoundVar(var) => ty::ConstKind::Bound(
-                ty::DebruijnIndex::from_u32(var.debruijn.depth()),
-                ty::BoundVar::from_u32(var.index as u32),
-            ),
-            chalk_ir::ConstValue::InferenceVar(_var) => unimplemented!(),
-            chalk_ir::ConstValue::Placeholder(_p) => unimplemented!(),
-            chalk_ir::ConstValue::Concrete(c) => ty::ConstKind::Value(c.interned),
-        };
-        interner.tcx.mk_const(kind, ty)
-    }
-}
-
-impl<'tcx> LowerInto<'tcx, chalk_ir::GenericArg<RustInterner<'tcx>>> for GenericArg<'tcx> {
-    fn lower_into(self, interner: RustInterner<'tcx>) -> chalk_ir::GenericArg<RustInterner<'tcx>> {
-        match self.unpack() {
-            ty::subst::GenericArgKind::Type(ty) => {
-                chalk_ir::GenericArgData::Ty(ty.lower_into(interner))
-            }
-            ty::subst::GenericArgKind::Lifetime(lifetime) => {
-                chalk_ir::GenericArgData::Lifetime(lifetime.lower_into(interner))
-            }
-            ty::subst::GenericArgKind::Const(c) => {
-                chalk_ir::GenericArgData::Const(c.lower_into(interner))
-            }
-        }
-        .intern(interner)
-    }
-}
-
-impl<'tcx> LowerInto<'tcx, ty::subst::GenericArg<'tcx>>
-    for &chalk_ir::GenericArg<RustInterner<'tcx>>
-{
-    fn lower_into(self, interner: RustInterner<'tcx>) -> ty::subst::GenericArg<'tcx> {
-        match self.data(interner) {
-            chalk_ir::GenericArgData::Ty(ty) => {
-                let t: Ty<'tcx> = ty.lower_into(interner);
-                t.into()
-            }
-            chalk_ir::GenericArgData::Lifetime(lifetime) => {
-                let r: Region<'tcx> = lifetime.lower_into(interner);
-                r.into()
-            }
-            chalk_ir::GenericArgData::Const(c) => {
-                let c: ty::Const<'tcx> = c.lower_into(interner);
-                c.into()
-            }
-        }
-    }
-}
-
-// We lower into an Option here since there are some predicates which Chalk
-// doesn't have a representation for yet (as a `WhereClause`), but are so common
-// that we just are accepting the unsoundness for now. The `Option` will
-// eventually be removed.
-impl<'tcx> LowerInto<'tcx, Option<chalk_ir::QuantifiedWhereClause<RustInterner<'tcx>>>>
-    for ty::Predicate<'tcx>
-{
-    fn lower_into(
-        self,
-        interner: RustInterner<'tcx>,
-    ) -> Option<chalk_ir::QuantifiedWhereClause<RustInterner<'tcx>>> {
-        let (predicate, binders, _named_regions) =
-            collect_bound_vars(interner, interner.tcx, self.kind());
-        let value = match predicate {
-            ty::PredicateKind::Clause(ty::Clause::Trait(predicate)) => {
-                Some(chalk_ir::WhereClause::Implemented(predicate.trait_ref.lower_into(interner)))
-            }
-            ty::PredicateKind::Clause(ty::Clause::RegionOutlives(predicate)) => {
-                Some(chalk_ir::WhereClause::LifetimeOutlives(chalk_ir::LifetimeOutlives {
-                    a: predicate.0.lower_into(interner),
-                    b: predicate.1.lower_into(interner),
-                }))
-            }
-            ty::PredicateKind::Clause(ty::Clause::TypeOutlives(predicate)) => {
-                Some(chalk_ir::WhereClause::TypeOutlives(chalk_ir::TypeOutlives {
-                    ty: predicate.0.lower_into(interner),
-                    lifetime: predicate.1.lower_into(interner),
-                }))
-            }
-            ty::PredicateKind::Clause(ty::Clause::Projection(predicate)) => {
-                Some(chalk_ir::WhereClause::AliasEq(predicate.lower_into(interner)))
-            }
-            ty::PredicateKind::WellFormed(_ty) => None,
-            ty::PredicateKind::Clause(ty::Clause::ConstArgHasType(..)) => None,
-
-            ty::PredicateKind::ObjectSafe(..)
-            | ty::PredicateKind::AliasRelate(..)
-            | ty::PredicateKind::ClosureKind(..)
-            | ty::PredicateKind::Subtype(..)
-            | ty::PredicateKind::Coerce(..)
-            | ty::PredicateKind::ConstEvaluatable(..)
-            | ty::PredicateKind::ConstEquate(..)
-            | ty::PredicateKind::Ambiguous
-            | ty::PredicateKind::TypeWellFormedFromEnv(..) => {
-                bug!("unexpected predicate {self}")
-            }
-        };
-        value.map(|value| chalk_ir::Binders::new(binders, value))
-    }
-}
-
-impl<'tcx> LowerInto<'tcx, chalk_ir::Binders<chalk_ir::QuantifiedWhereClauses<RustInterner<'tcx>>>>
-    for &'tcx ty::List<ty::PolyExistentialPredicate<'tcx>>
-{
-    fn lower_into(
-        self,
-        interner: RustInterner<'tcx>,
-    ) -> chalk_ir::Binders<chalk_ir::QuantifiedWhereClauses<RustInterner<'tcx>>> {
-        // `Self` has one binder:
-        // Binder<&'tcx ty::List<ty::ExistentialPredicate<'tcx>>>
-        // The return type has two:
-        // Binders<&[Binders<WhereClause<I>>]>
-        // This means that any variables that are escaping `self` need to be
-        // shifted in by one so that they are still escaping.
-        let predicates = ty::fold::shift_vars(interner.tcx, self, 1);
-
-        let self_ty = interner.tcx.mk_bound(
-            // This is going to be wrapped in a binder
-            ty::DebruijnIndex::from_usize(1),
-            ty::BoundTy { var: ty::BoundVar::from_usize(0), kind: ty::BoundTyKind::Anon },
-        );
-        let where_clauses = predicates.into_iter().map(|predicate| {
-            let (predicate, binders, _named_regions) =
-                collect_bound_vars(interner, interner.tcx, predicate);
-            match predicate {
-                ty::ExistentialPredicate::Trait(ty::ExistentialTraitRef { def_id, substs }) => {
-                    chalk_ir::Binders::new(
-                        binders.clone(),
-                        chalk_ir::WhereClause::Implemented(chalk_ir::TraitRef {
-                            trait_id: chalk_ir::TraitId(def_id),
-                            substitution: interner
-                                .tcx
-                                .mk_substs_trait(self_ty, substs)
-                                .lower_into(interner),
-                        }),
-                    )
-                }
-                ty::ExistentialPredicate::Projection(predicate) => chalk_ir::Binders::new(
-                    binders.clone(),
-                    chalk_ir::WhereClause::AliasEq(chalk_ir::AliasEq {
-                        alias: chalk_ir::AliasTy::Projection(chalk_ir::ProjectionTy {
-                            associated_ty_id: chalk_ir::AssocTypeId(predicate.def_id),
-                            substitution: interner
-                                .tcx
-                                .mk_substs_trait(self_ty, predicate.substs)
-                                .lower_into(interner),
-                        }),
-                        // FIXME(associated_const_equality): teach chalk about terms for alias eq.
-                        ty: predicate.term.ty().unwrap().lower_into(interner),
-                    }),
-                ),
-                ty::ExistentialPredicate::AutoTrait(def_id) => chalk_ir::Binders::new(
-                    binders.clone(),
-                    chalk_ir::WhereClause::Implemented(chalk_ir::TraitRef {
-                        trait_id: chalk_ir::TraitId(def_id),
-                        substitution: interner
-                            .tcx
-                            .mk_substs_trait(self_ty, [])
-                            .lower_into(interner),
-                    }),
-                ),
-            }
-        });
-
-        // Binder for the bound variable representing the concrete underlying type.
-        let existential_binder = chalk_ir::VariableKinds::from1(
-            interner,
-            chalk_ir::VariableKind::Ty(chalk_ir::TyVariableKind::General),
-        );
-        let value = chalk_ir::QuantifiedWhereClauses::from_iter(interner, where_clauses);
-        chalk_ir::Binders::new(existential_binder, value)
-    }
-}
-
-impl<'tcx> LowerInto<'tcx, chalk_ir::FnSig<RustInterner<'tcx>>>
-    for ty::Binder<'tcx, ty::FnSig<'tcx>>
-{
-    fn lower_into(self, _interner: RustInterner<'_>) -> FnSig<RustInterner<'tcx>> {
-        chalk_ir::FnSig {
-            abi: self.abi(),
-            safety: match self.unsafety() {
-                Unsafety::Normal => chalk_ir::Safety::Safe,
-                Unsafety::Unsafe => chalk_ir::Safety::Unsafe,
-            },
-            variadic: self.c_variadic(),
-        }
-    }
-}
-
-// We lower into an Option here since there are some predicates which Chalk
-// doesn't have a representation for yet (as an `InlineBound`). The `Option` will
-// eventually be removed.
-impl<'tcx> LowerInto<'tcx, Option<chalk_solve::rust_ir::QuantifiedInlineBound<RustInterner<'tcx>>>>
-    for ty::Predicate<'tcx>
-{
-    fn lower_into(
-        self,
-        interner: RustInterner<'tcx>,
-    ) -> Option<chalk_solve::rust_ir::QuantifiedInlineBound<RustInterner<'tcx>>> {
-        let (predicate, binders, _named_regions) =
-            collect_bound_vars(interner, interner.tcx, self.kind());
-        match predicate {
-            ty::PredicateKind::Clause(ty::Clause::Trait(predicate)) => {
-                Some(chalk_ir::Binders::new(
-                    binders,
-                    chalk_solve::rust_ir::InlineBound::TraitBound(
-                        predicate.trait_ref.lower_into(interner),
-                    ),
-                ))
-            }
-            ty::PredicateKind::Clause(ty::Clause::Projection(predicate)) => {
-                Some(chalk_ir::Binders::new(
-                    binders,
-                    chalk_solve::rust_ir::InlineBound::AliasEqBound(predicate.lower_into(interner)),
-                ))
-            }
-            ty::PredicateKind::Clause(ty::Clause::TypeOutlives(_predicate)) => None,
-            ty::PredicateKind::WellFormed(_ty) => None,
-            ty::PredicateKind::Clause(ty::Clause::ConstArgHasType(..)) => None,
-
-            ty::PredicateKind::Clause(ty::Clause::RegionOutlives(..))
-            | ty::PredicateKind::AliasRelate(..)
-            | ty::PredicateKind::ObjectSafe(..)
-            | ty::PredicateKind::ClosureKind(..)
-            | ty::PredicateKind::Subtype(..)
-            | ty::PredicateKind::Coerce(..)
-            | ty::PredicateKind::ConstEvaluatable(..)
-            | ty::PredicateKind::ConstEquate(..)
-            | ty::PredicateKind::Ambiguous
-            | ty::PredicateKind::TypeWellFormedFromEnv(..) => {
-                bug!("unexpected predicate {}", &self)
-            }
-        }
-    }
-}
-
-impl<'tcx> LowerInto<'tcx, chalk_solve::rust_ir::TraitBound<RustInterner<'tcx>>>
-    for ty::TraitRef<'tcx>
-{
-    fn lower_into(
-        self,
-        interner: RustInterner<'tcx>,
-    ) -> chalk_solve::rust_ir::TraitBound<RustInterner<'tcx>> {
-        chalk_solve::rust_ir::TraitBound {
-            trait_id: chalk_ir::TraitId(self.def_id),
-            args_no_self: self.substs[1..].iter().map(|arg| arg.lower_into(interner)).collect(),
-        }
-    }
-}
-
-impl<'tcx> LowerInto<'tcx, chalk_ir::Mutability> for ast::Mutability {
-    fn lower_into(self, _interner: RustInterner<'tcx>) -> chalk_ir::Mutability {
-        match self {
-            rustc_ast::Mutability::Mut => chalk_ir::Mutability::Mut,
-            rustc_ast::Mutability::Not => chalk_ir::Mutability::Not,
-        }
-    }
-}
-
-impl<'tcx> LowerInto<'tcx, ast::Mutability> for chalk_ir::Mutability {
-    fn lower_into(self, _interner: RustInterner<'tcx>) -> ast::Mutability {
-        match self {
-            chalk_ir::Mutability::Mut => ast::Mutability::Mut,
-            chalk_ir::Mutability::Not => ast::Mutability::Not,
-        }
-    }
-}
-
-impl<'tcx> LowerInto<'tcx, chalk_solve::rust_ir::Polarity> for ty::ImplPolarity {
-    fn lower_into(self, _interner: RustInterner<'tcx>) -> chalk_solve::rust_ir::Polarity {
-        match self {
-            ty::ImplPolarity::Positive => chalk_solve::rust_ir::Polarity::Positive,
-            ty::ImplPolarity::Negative => chalk_solve::rust_ir::Polarity::Negative,
-            // FIXME(chalk) reservation impls
-            ty::ImplPolarity::Reservation => chalk_solve::rust_ir::Polarity::Negative,
-        }
-    }
-}
-impl<'tcx> LowerInto<'tcx, chalk_ir::Variance> for ty::Variance {
-    fn lower_into(self, _interner: RustInterner<'tcx>) -> chalk_ir::Variance {
-        match self {
-            ty::Variance::Covariant => chalk_ir::Variance::Covariant,
-            ty::Variance::Invariant => chalk_ir::Variance::Invariant,
-            ty::Variance::Contravariant => chalk_ir::Variance::Contravariant,
-            ty::Variance::Bivariant => unimplemented!(),
-        }
-    }
-}
-
-impl<'tcx> LowerInto<'tcx, chalk_solve::rust_ir::AliasEqBound<RustInterner<'tcx>>>
-    for ty::ProjectionPredicate<'tcx>
-{
-    fn lower_into(
-        self,
-        interner: RustInterner<'tcx>,
-    ) -> chalk_solve::rust_ir::AliasEqBound<RustInterner<'tcx>> {
-        let (trait_ref, own_substs) = self.projection_ty.trait_ref_and_own_substs(interner.tcx);
-        chalk_solve::rust_ir::AliasEqBound {
-            trait_bound: trait_ref.lower_into(interner),
-            associated_ty_id: chalk_ir::AssocTypeId(self.projection_ty.def_id),
-            parameters: own_substs.iter().map(|arg| arg.lower_into(interner)).collect(),
-            value: self.term.ty().unwrap().lower_into(interner),
-        }
-    }
-}
-
-/// To collect bound vars, we have to do two passes. In the first pass, we
-/// collect all `BoundRegionKind`s and `ty::Bound`s. In the second pass, we then
-/// replace `BrNamed` into `BrAnon`. The two separate passes are important,
-/// since we can only replace `BrNamed` with `BrAnon`s with indices *after* all
-/// "real" `BrAnon`s.
-///
-/// It's important to note that because of prior substitution, we may have
-/// late-bound regions, even outside of fn contexts, since this is the best way
-/// to prep types for chalk lowering.
-pub(crate) fn collect_bound_vars<'tcx, T: TypeFoldable<TyCtxt<'tcx>>>(
-    interner: RustInterner<'tcx>,
-    tcx: TyCtxt<'tcx>,
-    ty: Binder<'tcx, T>,
-) -> (T, chalk_ir::VariableKinds<RustInterner<'tcx>>, BTreeMap<DefId, u32>) {
-    let mut bound_vars_collector = BoundVarsCollector::new();
-    ty.as_ref().skip_binder().visit_with(&mut bound_vars_collector);
-    let mut parameters = bound_vars_collector.parameters;
-    let named_parameters: BTreeMap<DefId, u32> = bound_vars_collector
-        .named_parameters
-        .into_iter()
-        .enumerate()
-        .map(|(i, def_id)| (def_id, (i + parameters.len()) as u32))
-        .collect();
-
-    let mut bound_var_substitutor = NamedBoundVarSubstitutor::new(tcx, &named_parameters);
-    let new_ty = ty.skip_binder().fold_with(&mut bound_var_substitutor);
-
-    for var in named_parameters.values() {
-        parameters.insert(*var, chalk_ir::VariableKind::Lifetime);
-    }
-
-    (0..parameters.len()).for_each(|i| {
-        parameters
-            .get(&(i as u32))
-            .or_else(|| bug!("Skipped bound var index: parameters={:?}", parameters));
-    });
-
-    let binders = chalk_ir::VariableKinds::from_iter(interner, parameters.into_values());
-
-    (new_ty, binders, named_parameters)
-}
-
-pub(crate) struct BoundVarsCollector<'tcx> {
-    binder_index: ty::DebruijnIndex,
-    pub(crate) parameters: BTreeMap<u32, chalk_ir::VariableKind<RustInterner<'tcx>>>,
-    pub(crate) named_parameters: Vec<DefId>,
-}
-
-impl<'tcx> BoundVarsCollector<'tcx> {
-    pub(crate) fn new() -> Self {
-        BoundVarsCollector {
-            binder_index: ty::INNERMOST,
-            parameters: BTreeMap::new(),
-            named_parameters: vec![],
-        }
-    }
-}
-
-impl<'tcx> TypeVisitor<TyCtxt<'tcx>> for BoundVarsCollector<'tcx> {
-    fn visit_binder<T: TypeVisitable<TyCtxt<'tcx>>>(
-        &mut self,
-        t: &Binder<'tcx, T>,
-    ) -> ControlFlow<Self::BreakTy> {
-        self.binder_index.shift_in(1);
-        let result = t.super_visit_with(self);
-        self.binder_index.shift_out(1);
-        result
-    }
-
-    fn visit_ty(&mut self, t: Ty<'tcx>) -> ControlFlow<Self::BreakTy> {
-        match *t.kind() {
-            ty::Bound(debruijn, bound_ty) if debruijn == self.binder_index => {
-                match self.parameters.entry(bound_ty.var.as_u32()) {
-                    Entry::Vacant(entry) => {
-                        entry.insert(chalk_ir::VariableKind::Ty(chalk_ir::TyVariableKind::General));
-                    }
-                    Entry::Occupied(entry) => match entry.get() {
-                        chalk_ir::VariableKind::Ty(_) => {}
-                        _ => panic!(),
-                    },
-                }
-            }
-
-            _ => (),
-        };
-
-        t.super_visit_with(self)
-    }
-
-    fn visit_region(&mut self, r: Region<'tcx>) -> ControlFlow<Self::BreakTy> {
-        match *r {
-            ty::ReLateBound(index, br) if index == self.binder_index => match br.kind {
-                ty::BoundRegionKind::BrNamed(def_id, _name) => {
-                    if !self.named_parameters.iter().any(|d| *d == def_id) {
-                        self.named_parameters.push(def_id);
-                    }
-                }
-
-                ty::BoundRegionKind::BrAnon(_) => match self.parameters.entry(br.var.as_u32()) {
-                    Entry::Vacant(entry) => {
-                        entry.insert(chalk_ir::VariableKind::Lifetime);
-                    }
-                    Entry::Occupied(entry) => match entry.get() {
-                        chalk_ir::VariableKind::Lifetime => {}
-                        _ => panic!(),
-                    },
-                },
-
-                ty::BoundRegionKind::BrEnv => unimplemented!(),
-            },
-
-            ty::ReEarlyBound(_re) => {
-                // FIXME(chalk): jackh726 - I think we should always have already
-                // substituted away `ReEarlyBound`s for `ReLateBound`s, but need to confirm.
-                unimplemented!();
-            }
-
-            _ => (),
-        };
-
-        ControlFlow::Continue(())
-    }
-}
-
-/// This is used to replace `BoundRegionKind::BrNamed` with `BoundRegionKind::BrAnon`.
-/// Note: we assume that we will always have room for more bound vars. (i.e. we
-/// won't ever hit the `u32` limit in `BrAnon`s).
-struct NamedBoundVarSubstitutor<'a, 'tcx> {
-    tcx: TyCtxt<'tcx>,
-    binder_index: ty::DebruijnIndex,
-    named_parameters: &'a BTreeMap<DefId, u32>,
-}
-
-impl<'a, 'tcx> NamedBoundVarSubstitutor<'a, 'tcx> {
-    fn new(tcx: TyCtxt<'tcx>, named_parameters: &'a BTreeMap<DefId, u32>) -> Self {
-        NamedBoundVarSubstitutor { tcx, binder_index: ty::INNERMOST, named_parameters }
-    }
-}
-
-impl<'a, 'tcx> TypeFolder<TyCtxt<'tcx>> for NamedBoundVarSubstitutor<'a, 'tcx> {
-    fn interner(&self) -> TyCtxt<'tcx> {
-        self.tcx
-    }
-
-    fn fold_binder<T: TypeFoldable<TyCtxt<'tcx>>>(
-        &mut self,
-        t: Binder<'tcx, T>,
-    ) -> Binder<'tcx, T> {
-        self.binder_index.shift_in(1);
-        let result = t.super_fold_with(self);
-        self.binder_index.shift_out(1);
-        result
-    }
-
-    fn fold_region(&mut self, r: Region<'tcx>) -> Region<'tcx> {
-        match *r {
-            ty::ReLateBound(index, br) if index == self.binder_index => match br.kind {
-                ty::BrNamed(def_id, _name) => match self.named_parameters.get(&def_id) {
-                    Some(_) => {
-                        let new_br = ty::BoundRegion { var: br.var, kind: ty::BrAnon(None) };
-                        return self.tcx.mk_re_late_bound(index, new_br);
-                    }
-                    None => panic!("Missing `BrNamed`."),
-                },
-                ty::BrEnv => unimplemented!(),
-                ty::BrAnon(..) => {}
-            },
-            _ => (),
-        };
-
-        r
-    }
-}
-
-/// Used to substitute `Param`s with placeholders. We do this since Chalk
-/// have a notion of `Param`s.
-pub(crate) struct ParamsSubstitutor<'tcx> {
-    tcx: TyCtxt<'tcx>,
-    binder_index: ty::DebruijnIndex,
-    list: Vec<rustc_middle::ty::ParamTy>,
-    next_ty_placeholder: usize,
-    pub(crate) params: rustc_data_structures::fx::FxHashMap<u32, rustc_middle::ty::ParamTy>,
-    pub(crate) named_regions: BTreeMap<DefId, u32>,
-}
-
-impl<'tcx> ParamsSubstitutor<'tcx> {
-    pub(crate) fn new(tcx: TyCtxt<'tcx>, next_ty_placeholder: usize) -> Self {
-        ParamsSubstitutor {
-            tcx,
-            binder_index: ty::INNERMOST,
-            list: vec![],
-            next_ty_placeholder,
-            params: rustc_data_structures::fx::FxHashMap::default(),
-            named_regions: BTreeMap::default(),
-        }
-    }
-}
-
-impl<'tcx> TypeFolder<TyCtxt<'tcx>> for ParamsSubstitutor<'tcx> {
-    fn interner(&self) -> TyCtxt<'tcx> {
-        self.tcx
-    }
-
-    fn fold_binder<T: TypeFoldable<TyCtxt<'tcx>>>(
-        &mut self,
-        t: Binder<'tcx, T>,
-    ) -> Binder<'tcx, T> {
-        self.binder_index.shift_in(1);
-        let result = t.super_fold_with(self);
-        self.binder_index.shift_out(1);
-        result
-    }
-
-    fn fold_ty(&mut self, t: Ty<'tcx>) -> Ty<'tcx> {
-        match *t.kind() {
-            ty::Param(param) => match self.list.iter().position(|r| r == &param) {
-                Some(idx) => self.tcx.mk_placeholder(ty::PlaceholderType {
-                    universe: ty::UniverseIndex::from_usize(0),
-                    bound: ty::BoundTy {
-                        var: ty::BoundVar::from_usize(idx),
-                        kind: ty::BoundTyKind::Anon,
-                    },
-                }),
-                None => {
-                    self.list.push(param);
-                    let idx = self.list.len() - 1 + self.next_ty_placeholder;
-                    self.params.insert(idx as u32, param);
-                    self.tcx.mk_placeholder(ty::PlaceholderType {
-                        universe: ty::UniverseIndex::from_usize(0),
-                        bound: ty::BoundTy {
-                            var: ty::BoundVar::from_usize(idx),
-                            kind: ty::BoundTyKind::Anon,
-                        },
-                    })
-                }
-            },
-            _ => t.super_fold_with(self),
-        }
-    }
-
-    fn fold_region(&mut self, r: Region<'tcx>) -> Region<'tcx> {
-        match *r {
-            // FIXME(chalk) - jackh726 - this currently isn't hit in any tests,
-            // since canonicalization will already change these to canonical
-            // variables (ty::ReLateBound).
-            ty::ReEarlyBound(_re) => match self.named_regions.get(&_re.def_id) {
-                Some(idx) => {
-                    let br = ty::BoundRegion {
-                        var: ty::BoundVar::from_u32(*idx),
-                        kind: ty::BrAnon(None),
-                    };
-                    self.tcx.mk_re_late_bound(self.binder_index, br)
-                }
-                None => {
-                    let idx = self.named_regions.len() as u32;
-                    let br = ty::BoundRegion {
-                        var: ty::BoundVar::from_u32(idx),
-                        kind: ty::BrAnon(None),
-                    };
-                    self.named_regions.insert(_re.def_id, idx);
-                    self.tcx.mk_re_late_bound(self.binder_index, br)
-                }
-            },
-
-            _ => r,
-        }
-    }
-}
-
-pub(crate) struct ReverseParamsSubstitutor<'tcx> {
-    tcx: TyCtxt<'tcx>,
-    params: rustc_data_structures::fx::FxHashMap<u32, rustc_middle::ty::ParamTy>,
-}
-
-impl<'tcx> ReverseParamsSubstitutor<'tcx> {
-    pub(crate) fn new(
-        tcx: TyCtxt<'tcx>,
-        params: rustc_data_structures::fx::FxHashMap<u32, rustc_middle::ty::ParamTy>,
-    ) -> Self {
-        Self { tcx, params }
-    }
-}
-
-impl<'tcx> TypeFolder<TyCtxt<'tcx>> for ReverseParamsSubstitutor<'tcx> {
-    fn interner(&self) -> TyCtxt<'tcx> {
-        self.tcx
-    }
-
-    fn fold_ty(&mut self, t: Ty<'tcx>) -> Ty<'tcx> {
-        match *t.kind() {
-            ty::Placeholder(ty::PlaceholderType { universe: ty::UniverseIndex::ROOT, bound }) => {
-                match self.params.get(&bound.var.as_u32()) {
-                    Some(&ty::ParamTy { index, name }) => self.tcx.mk_ty_param(index, name),
-                    None => t,
-                }
-            }
-
-            _ => t.super_fold_with(self),
-        }
-    }
-}
-
-/// Used to collect `Placeholder`s.
-pub(crate) struct PlaceholdersCollector {
-    universe_index: ty::UniverseIndex,
-    pub(crate) next_ty_placeholder: usize,
-    pub(crate) next_anon_region_placeholder: u32,
-}
-
-impl PlaceholdersCollector {
-    pub(crate) fn new() -> Self {
-        PlaceholdersCollector {
-            universe_index: ty::UniverseIndex::ROOT,
-            next_ty_placeholder: 0,
-            next_anon_region_placeholder: 0,
-        }
-    }
-}
-
-impl<'tcx> TypeVisitor<TyCtxt<'tcx>> for PlaceholdersCollector {
-    fn visit_ty(&mut self, t: Ty<'tcx>) -> ControlFlow<Self::BreakTy> {
-        match t.kind() {
-            ty::Placeholder(p) if p.universe == self.universe_index => {
-                self.next_ty_placeholder = self.next_ty_placeholder.max(p.bound.var.as_usize() + 1);
-            }
-
-            _ => (),
-        };
-
-        t.super_visit_with(self)
-    }
-
-    fn visit_region(&mut self, r: Region<'tcx>) -> ControlFlow<Self::BreakTy> {
-        match *r {
-            ty::RePlaceholder(p) if p.universe == self.universe_index => {
-                if let ty::BoundRegionKind::BrAnon(_) = p.bound.kind {
-                    self.next_anon_region_placeholder =
-                        self.next_anon_region_placeholder.max(p.bound.var.as_u32());
-                }
-                // FIXME: This doesn't seem to handle BrNamed at all?
-            }
-
-            _ => (),
-        };
-
-        ControlFlow::Continue(())
-    }
-}