Adding upstream version 1.64.0+dfsg1.upstream/1.64.0+dfsg1

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

3 files changed, 2144 insertions, 0 deletions

diff --git a/compiler/rustc_traits/src/chalk/db.rs b/compiler/rustc_traits/src/chalk/db.rs
new file mode 100644
index 000000000..ff5ca0cbc
--- /dev/null
+++ b/compiler/rustc_traits/src/chalk/db.rs
@@ -0,0 +1,796 @@
+//! Provides the `RustIrDatabase` implementation for `chalk-solve`
+//!
+//! The purpose of the `chalk_solve::RustIrDatabase` is to get data about
+//! specific types, such as bounds, where clauses, or fields. This file contains
+//! the minimal logic to assemble the types for `chalk-solve` by calling out to
+//! either the `TyCtxt` (for information about types) or
+//! `crate::chalk::lowering` (to lower rustc types into Chalk types).
+
+use rustc_middle::traits::ChalkRustInterner as RustInterner;
+use rustc_middle::ty::subst::{InternalSubsts, Subst, SubstsRef};
+use rustc_middle::ty::{self, AssocKind, EarlyBinder, Ty, TyCtxt, TypeFoldable, TypeSuperFoldable};
+
+use rustc_ast::ast;
+use rustc_attr as attr;
+
+use rustc_hir::def_id::DefId;
+
+use rustc_span::symbol::sym;
+
+use std::fmt;
+use std::sync::Arc;
+
+use crate::chalk::lowering::LowerInto;
+
+pub struct RustIrDatabase<'tcx> {
+    pub(crate) interner: RustInterner<'tcx>,
+}
+
+impl fmt::Debug for RustIrDatabase<'_> {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        write!(f, "RustIrDatabase")
+    }
+}
+
+impl<'tcx> RustIrDatabase<'tcx> {
+    fn where_clauses_for(
+        &self,
+        def_id: DefId,
+        bound_vars: SubstsRef<'tcx>,
+    ) -> Vec<chalk_ir::QuantifiedWhereClause<RustInterner<'tcx>>> {
+        let predicates = self.interner.tcx.predicates_defined_on(def_id).predicates;
+        predicates
+            .iter()
+            .map(|(wc, _)| EarlyBinder(*wc).subst(self.interner.tcx, bound_vars))
+            .filter_map(|wc| LowerInto::<
+                    Option<chalk_ir::QuantifiedWhereClause<RustInterner<'tcx>>>
+                    >::lower_into(wc, self.interner)).collect()
+    }
+
+    fn bounds_for<T>(&self, def_id: DefId, bound_vars: SubstsRef<'tcx>) -> Vec<T>
+    where
+        ty::Predicate<'tcx>: LowerInto<'tcx, std::option::Option<T>>,
+    {
+        let bounds = self.interner.tcx.bound_explicit_item_bounds(def_id);
+        bounds
+            .0
+            .iter()
+            .map(|(bound, _)| bounds.rebind(*bound).subst(self.interner.tcx, &bound_vars))
+            .filter_map(|bound| LowerInto::<Option<_>>::lower_into(bound, self.interner))
+            .collect()
+    }
+}
+
+impl<'tcx> chalk_solve::RustIrDatabase<RustInterner<'tcx>> for RustIrDatabase<'tcx> {
+    fn interner(&self) -> RustInterner<'tcx> {
+        self.interner
+    }
+
+    fn associated_ty_data(
+        &self,
+        assoc_type_id: chalk_ir::AssocTypeId<RustInterner<'tcx>>,
+    ) -> Arc<chalk_solve::rust_ir::AssociatedTyDatum<RustInterner<'tcx>>> {
+        let def_id = assoc_type_id.0;
+        let assoc_item = self.interner.tcx.associated_item(def_id);
+        let Some(trait_def_id) = assoc_item.trait_container(self.interner.tcx) else {
+            unimplemented!("Not possible??");
+        };
+        match assoc_item.kind {
+            AssocKind::Type => {}
+            _ => unimplemented!("Not possible??"),
+        }
+        let bound_vars = bound_vars_for_item(self.interner.tcx, def_id);
+        let binders = binders_for(self.interner, bound_vars);
+
+        let where_clauses = self.where_clauses_for(def_id, bound_vars);
+        let bounds = self.bounds_for(def_id, bound_vars);
+
+        Arc::new(chalk_solve::rust_ir::AssociatedTyDatum {
+            trait_id: chalk_ir::TraitId(trait_def_id),
+            id: assoc_type_id,
+            name: (),
+            binders: chalk_ir::Binders::new(
+                binders,
+                chalk_solve::rust_ir::AssociatedTyDatumBound { bounds, where_clauses },
+            ),
+        })
+    }
+
+    fn trait_datum(
+        &self,
+        trait_id: chalk_ir::TraitId<RustInterner<'tcx>>,
+    ) -> Arc<chalk_solve::rust_ir::TraitDatum<RustInterner<'tcx>>> {
+        use chalk_solve::rust_ir::WellKnownTrait::*;
+
+        let def_id = trait_id.0;
+        let trait_def = self.interner.tcx.trait_def(def_id);
+
+        let bound_vars = bound_vars_for_item(self.interner.tcx, def_id);
+        let binders = binders_for(self.interner, bound_vars);
+
+        let where_clauses = self.where_clauses_for(def_id, bound_vars);
+
+        let associated_ty_ids: Vec<_> = self
+            .interner
+            .tcx
+            .associated_items(def_id)
+            .in_definition_order()
+            .filter(|i| i.kind == AssocKind::Type)
+            .map(|i| chalk_ir::AssocTypeId(i.def_id))
+            .collect();
+
+        let lang_items = self.interner.tcx.lang_items();
+        let well_known = if lang_items.sized_trait() == Some(def_id) {
+            Some(Sized)
+        } else if lang_items.copy_trait() == Some(def_id) {
+            Some(Copy)
+        } else if lang_items.clone_trait() == Some(def_id) {
+            Some(Clone)
+        } else if lang_items.drop_trait() == Some(def_id) {
+            Some(Drop)
+        } else if lang_items.fn_trait() == Some(def_id) {
+            Some(Fn)
+        } else if lang_items.fn_once_trait() == Some(def_id) {
+            Some(FnOnce)
+        } else if lang_items.fn_mut_trait() == Some(def_id) {
+            Some(FnMut)
+        } else if lang_items.unsize_trait() == Some(def_id) {
+            Some(Unsize)
+        } else if lang_items.unpin_trait() == Some(def_id) {
+            Some(Unpin)
+        } else if lang_items.coerce_unsized_trait() == Some(def_id) {
+            Some(CoerceUnsized)
+        } else if lang_items.dispatch_from_dyn_trait() == Some(def_id) {
+            Some(DispatchFromDyn)
+        } else {
+            None
+        };
+        Arc::new(chalk_solve::rust_ir::TraitDatum {
+            id: trait_id,
+            binders: chalk_ir::Binders::new(
+                binders,
+                chalk_solve::rust_ir::TraitDatumBound { where_clauses },
+            ),
+            flags: chalk_solve::rust_ir::TraitFlags {
+                auto: trait_def.has_auto_impl,
+                marker: trait_def.is_marker,
+                upstream: !def_id.is_local(),
+                fundamental: self.interner.tcx.has_attr(def_id, sym::fundamental),
+                non_enumerable: true,
+                coinductive: false,
+            },
+            associated_ty_ids,
+            well_known,
+        })
+    }
+
+    fn adt_datum(
+        &self,
+        adt_id: chalk_ir::AdtId<RustInterner<'tcx>>,
+    ) -> Arc<chalk_solve::rust_ir::AdtDatum<RustInterner<'tcx>>> {
+        let adt_def = adt_id.0;
+
+        let bound_vars = bound_vars_for_item(self.interner.tcx, adt_def.did());
+        let binders = binders_for(self.interner, bound_vars);
+
+        let where_clauses = self.where_clauses_for(adt_def.did(), bound_vars);
+
+        let variants: Vec<_> = adt_def
+            .variants()
+            .iter()
+            .map(|variant| chalk_solve::rust_ir::AdtVariantDatum {
+                fields: variant
+                    .fields
+                    .iter()
+                    .map(|field| field.ty(self.interner.tcx, bound_vars).lower_into(self.interner))
+                    .collect(),
+            })
+            .collect();
+        Arc::new(chalk_solve::rust_ir::AdtDatum {
+            id: adt_id,
+            binders: chalk_ir::Binders::new(
+                binders,
+                chalk_solve::rust_ir::AdtDatumBound { variants, where_clauses },
+            ),
+            flags: chalk_solve::rust_ir::AdtFlags {
+                upstream: !adt_def.did().is_local(),
+                fundamental: adt_def.is_fundamental(),
+                phantom_data: adt_def.is_phantom_data(),
+            },
+            kind: match adt_def.adt_kind() {
+                ty::AdtKind::Struct => chalk_solve::rust_ir::AdtKind::Struct,
+                ty::AdtKind::Union => chalk_solve::rust_ir::AdtKind::Union,
+                ty::AdtKind::Enum => chalk_solve::rust_ir::AdtKind::Enum,
+            },
+        })
+    }
+
+    fn adt_repr(
+        &self,
+        adt_id: chalk_ir::AdtId<RustInterner<'tcx>>,
+    ) -> Arc<chalk_solve::rust_ir::AdtRepr<RustInterner<'tcx>>> {
+        let adt_def = adt_id.0;
+        let int = |i| chalk_ir::TyKind::Scalar(chalk_ir::Scalar::Int(i)).intern(self.interner);
+        let uint = |i| chalk_ir::TyKind::Scalar(chalk_ir::Scalar::Uint(i)).intern(self.interner);
+        Arc::new(chalk_solve::rust_ir::AdtRepr {
+            c: adt_def.repr().c(),
+            packed: adt_def.repr().packed(),
+            int: adt_def.repr().int.map(|i| match i {
+                attr::IntType::SignedInt(ty) => match ty {
+                    ast::IntTy::Isize => int(chalk_ir::IntTy::Isize),
+                    ast::IntTy::I8 => int(chalk_ir::IntTy::I8),
+                    ast::IntTy::I16 => int(chalk_ir::IntTy::I16),
+                    ast::IntTy::I32 => int(chalk_ir::IntTy::I32),
+                    ast::IntTy::I64 => int(chalk_ir::IntTy::I64),
+                    ast::IntTy::I128 => int(chalk_ir::IntTy::I128),
+                },
+                attr::IntType::UnsignedInt(ty) => match ty {
+                    ast::UintTy::Usize => uint(chalk_ir::UintTy::Usize),
+                    ast::UintTy::U8 => uint(chalk_ir::UintTy::U8),
+                    ast::UintTy::U16 => uint(chalk_ir::UintTy::U16),
+                    ast::UintTy::U32 => uint(chalk_ir::UintTy::U32),
+                    ast::UintTy::U64 => uint(chalk_ir::UintTy::U64),
+                    ast::UintTy::U128 => uint(chalk_ir::UintTy::U128),
+                },
+            }),
+        })
+    }
+
+    fn adt_size_align(
+        &self,
+        adt_id: chalk_ir::AdtId<RustInterner<'tcx>>,
+    ) -> Arc<chalk_solve::rust_ir::AdtSizeAlign> {
+        let tcx = self.interner.tcx;
+        let did = adt_id.0.did();
+
+        // Grab the ADT and the param we might need to calculate its layout
+        let param_env = tcx.param_env(did);
+        let adt_ty = tcx.type_of(did);
+
+        // The ADT is a 1-zst if it's a ZST and its alignment is 1.
+        // Mark the ADT as _not_ a 1-zst if there was a layout error.
+        let one_zst = if let Ok(layout) = tcx.layout_of(param_env.and(adt_ty)) {
+            layout.is_zst() && layout.align.abi.bytes() == 1
+        } else {
+            false
+        };
+
+        Arc::new(chalk_solve::rust_ir::AdtSizeAlign::from_one_zst(one_zst))
+    }
+
+    fn fn_def_datum(
+        &self,
+        fn_def_id: chalk_ir::FnDefId<RustInterner<'tcx>>,
+    ) -> Arc<chalk_solve::rust_ir::FnDefDatum<RustInterner<'tcx>>> {
+        let def_id = fn_def_id.0;
+        let bound_vars = bound_vars_for_item(self.interner.tcx, def_id);
+        let binders = binders_for(self.interner, bound_vars);
+
+        let where_clauses = self.where_clauses_for(def_id, bound_vars);
+
+        let sig = self.interner.tcx.bound_fn_sig(def_id);
+        let (inputs_and_output, iobinders, _) = crate::chalk::lowering::collect_bound_vars(
+            self.interner,
+            self.interner.tcx,
+            sig.map_bound(|s| s.inputs_and_output()).subst(self.interner.tcx, bound_vars),
+        );
+
+        let argument_types = inputs_and_output[..inputs_and_output.len() - 1]
+            .iter()
+            .map(|t| sig.rebind(*t).subst(self.interner.tcx, &bound_vars).lower_into(self.interner))
+            .collect();
+
+        let return_type = sig
+            .rebind(inputs_and_output[inputs_and_output.len() - 1])
+            .subst(self.interner.tcx, &bound_vars)
+            .lower_into(self.interner);
+
+        let bound = chalk_solve::rust_ir::FnDefDatumBound {
+            inputs_and_output: chalk_ir::Binders::new(
+                iobinders,
+                chalk_solve::rust_ir::FnDefInputsAndOutputDatum { argument_types, return_type },
+            ),
+            where_clauses,
+        };
+        Arc::new(chalk_solve::rust_ir::FnDefDatum {
+            id: fn_def_id,
+            sig: sig.0.lower_into(self.interner),
+            binders: chalk_ir::Binders::new(binders, bound),
+        })
+    }
+
+    fn impl_datum(
+        &self,
+        impl_id: chalk_ir::ImplId<RustInterner<'tcx>>,
+    ) -> Arc<chalk_solve::rust_ir::ImplDatum<RustInterner<'tcx>>> {
+        let def_id = impl_id.0;
+        let bound_vars = bound_vars_for_item(self.interner.tcx, def_id);
+        let binders = binders_for(self.interner, bound_vars);
+
+        let trait_ref = self.interner.tcx.bound_impl_trait_ref(def_id).expect("not an impl");
+        let trait_ref = trait_ref.subst(self.interner.tcx, bound_vars);
+
+        let where_clauses = self.where_clauses_for(def_id, bound_vars);
+
+        let value = chalk_solve::rust_ir::ImplDatumBound {
+            trait_ref: trait_ref.lower_into(self.interner),
+            where_clauses,
+        };
+
+        let associated_ty_value_ids: Vec<_> = self
+            .interner
+            .tcx
+            .associated_items(def_id)
+            .in_definition_order()
+            .filter(|i| i.kind == AssocKind::Type)
+            .map(|i| chalk_solve::rust_ir::AssociatedTyValueId(i.def_id))
+            .collect();
+
+        Arc::new(chalk_solve::rust_ir::ImplDatum {
+            polarity: self.interner.tcx.impl_polarity(def_id).lower_into(self.interner),
+            binders: chalk_ir::Binders::new(binders, value),
+            impl_type: chalk_solve::rust_ir::ImplType::Local,
+            associated_ty_value_ids,
+        })
+    }
+
+    fn impls_for_trait(
+        &self,
+        trait_id: chalk_ir::TraitId<RustInterner<'tcx>>,
+        parameters: &[chalk_ir::GenericArg<RustInterner<'tcx>>],
+        _binders: &chalk_ir::CanonicalVarKinds<RustInterner<'tcx>>,
+    ) -> Vec<chalk_ir::ImplId<RustInterner<'tcx>>> {
+        let def_id = trait_id.0;
+
+        // FIXME(chalk): use TraitDef::for_each_relevant_impl, but that will
+        // require us to be able to interconvert `Ty<'tcx>`, and we're
+        // not there yet.
+
+        let all_impls = self.interner.tcx.all_impls(def_id);
+        let matched_impls = all_impls.filter(|impl_def_id| {
+            use chalk_ir::could_match::CouldMatch;
+            let trait_ref = self.interner.tcx.bound_impl_trait_ref(*impl_def_id).unwrap();
+            let bound_vars = bound_vars_for_item(self.interner.tcx, *impl_def_id);
+
+            let self_ty = trait_ref.map_bound(|t| t.self_ty());
+            let self_ty = self_ty.subst(self.interner.tcx, bound_vars);
+            let lowered_ty = self_ty.lower_into(self.interner);
+
+            parameters[0].assert_ty_ref(self.interner).could_match(
+                self.interner,
+                self.unification_database(),
+                &lowered_ty,
+            )
+        });
+
+        let impls = matched_impls.map(chalk_ir::ImplId).collect();
+        impls
+    }
+
+    fn impl_provided_for(
+        &self,
+        auto_trait_id: chalk_ir::TraitId<RustInterner<'tcx>>,
+        chalk_ty: &chalk_ir::TyKind<RustInterner<'tcx>>,
+    ) -> bool {
+        use chalk_ir::Scalar::*;
+        use chalk_ir::TyKind::*;
+
+        let trait_def_id = auto_trait_id.0;
+        let all_impls = self.interner.tcx.all_impls(trait_def_id);
+        for impl_def_id in all_impls {
+            let trait_ref = self.interner.tcx.impl_trait_ref(impl_def_id).unwrap();
+            let self_ty = trait_ref.self_ty();
+            let provides = match (self_ty.kind(), chalk_ty) {
+                (&ty::Adt(impl_adt_def, ..), Adt(id, ..)) => impl_adt_def.did() == id.0.did(),
+                (_, AssociatedType(_ty_id, ..)) => {
+                    // FIXME(chalk): See https://github.com/rust-lang/rust/pull/77152#discussion_r494484774
+                    false
+                }
+                (ty::Bool, Scalar(Bool)) => true,
+                (ty::Char, Scalar(Char)) => true,
+                (ty::Int(ty1), Scalar(Int(ty2))) => matches!(
+                    (ty1, ty2),
+                    (ty::IntTy::Isize, chalk_ir::IntTy::Isize)
+                        | (ty::IntTy::I8, chalk_ir::IntTy::I8)
+                        | (ty::IntTy::I16, chalk_ir::IntTy::I16)
+                        | (ty::IntTy::I32, chalk_ir::IntTy::I32)
+                        | (ty::IntTy::I64, chalk_ir::IntTy::I64)
+                        | (ty::IntTy::I128, chalk_ir::IntTy::I128)
+                ),
+                (ty::Uint(ty1), Scalar(Uint(ty2))) => matches!(
+                    (ty1, ty2),
+                    (ty::UintTy::Usize, chalk_ir::UintTy::Usize)
+                        | (ty::UintTy::U8, chalk_ir::UintTy::U8)
+                        | (ty::UintTy::U16, chalk_ir::UintTy::U16)
+                        | (ty::UintTy::U32, chalk_ir::UintTy::U32)
+                        | (ty::UintTy::U64, chalk_ir::UintTy::U64)
+                        | (ty::UintTy::U128, chalk_ir::UintTy::U128)
+                ),
+                (ty::Float(ty1), Scalar(Float(ty2))) => matches!(
+                    (ty1, ty2),
+                    (ty::FloatTy::F32, chalk_ir::FloatTy::F32)
+                        | (ty::FloatTy::F64, chalk_ir::FloatTy::F64)
+                ),
+                (&ty::Tuple(substs), Tuple(len, _)) => substs.len() == *len,
+                (&ty::Array(..), Array(..)) => true,
+                (&ty::Slice(..), Slice(..)) => true,
+                (&ty::RawPtr(type_and_mut), Raw(mutability, _)) => {
+                    match (type_and_mut.mutbl, mutability) {
+                        (ast::Mutability::Mut, chalk_ir::Mutability::Mut) => true,
+                        (ast::Mutability::Mut, chalk_ir::Mutability::Not) => false,
+                        (ast::Mutability::Not, chalk_ir::Mutability::Mut) => false,
+                        (ast::Mutability::Not, chalk_ir::Mutability::Not) => true,
+                    }
+                }
+                (&ty::Ref(.., mutability1), Ref(mutability2, ..)) => {
+                    match (mutability1, mutability2) {
+                        (ast::Mutability::Mut, chalk_ir::Mutability::Mut) => true,
+                        (ast::Mutability::Mut, chalk_ir::Mutability::Not) => false,
+                        (ast::Mutability::Not, chalk_ir::Mutability::Mut) => false,
+                        (ast::Mutability::Not, chalk_ir::Mutability::Not) => true,
+                    }
+                }
+                (&ty::Opaque(def_id, ..), OpaqueType(opaque_ty_id, ..)) => def_id == opaque_ty_id.0,
+                (&ty::FnDef(def_id, ..), FnDef(fn_def_id, ..)) => def_id == fn_def_id.0,
+                (&ty::Str, Str) => true,
+                (&ty::Never, Never) => true,
+                (&ty::Closure(def_id, ..), Closure(closure_id, _)) => def_id == closure_id.0,
+                (&ty::Foreign(def_id), Foreign(foreign_def_id)) => def_id == foreign_def_id.0,
+                (&ty::Error(..), Error) => false,
+                _ => false,
+            };
+            if provides {
+                return true;
+            }
+        }
+        false
+    }
+
+    fn associated_ty_value(
+        &self,
+        associated_ty_id: chalk_solve::rust_ir::AssociatedTyValueId<RustInterner<'tcx>>,
+    ) -> Arc<chalk_solve::rust_ir::AssociatedTyValue<RustInterner<'tcx>>> {
+        let def_id = associated_ty_id.0;
+        let assoc_item = self.interner.tcx.associated_item(def_id);
+        let impl_id = assoc_item.container_id(self.interner.tcx);
+        match assoc_item.kind {
+            AssocKind::Type => {}
+            _ => unimplemented!("Not possible??"),
+        }
+
+        let trait_item_id = assoc_item.trait_item_def_id.expect("assoc_ty with no trait version");
+        let bound_vars = bound_vars_for_item(self.interner.tcx, def_id);
+        let binders = binders_for(self.interner, bound_vars);
+        let ty = self
+            .interner
+            .tcx
+            .bound_type_of(def_id)
+            .subst(self.interner.tcx, bound_vars)
+            .lower_into(self.interner);
+
+        Arc::new(chalk_solve::rust_ir::AssociatedTyValue {
+            impl_id: chalk_ir::ImplId(impl_id),
+            associated_ty_id: chalk_ir::AssocTypeId(trait_item_id),
+            value: chalk_ir::Binders::new(
+                binders,
+                chalk_solve::rust_ir::AssociatedTyValueBound { ty },
+            ),
+        })
+    }
+
+    fn custom_clauses(&self) -> Vec<chalk_ir::ProgramClause<RustInterner<'tcx>>> {
+        vec![]
+    }
+
+    fn local_impls_to_coherence_check(
+        &self,
+        _trait_id: chalk_ir::TraitId<RustInterner<'tcx>>,
+    ) -> Vec<chalk_ir::ImplId<RustInterner<'tcx>>> {
+        unimplemented!()
+    }
+
+    fn opaque_ty_data(
+        &self,
+        opaque_ty_id: chalk_ir::OpaqueTyId<RustInterner<'tcx>>,
+    ) -> Arc<chalk_solve::rust_ir::OpaqueTyDatum<RustInterner<'tcx>>> {
+        let bound_vars = ty::fold::shift_vars(
+            self.interner.tcx,
+            bound_vars_for_item(self.interner.tcx, opaque_ty_id.0),
+            1,
+        );
+        let where_clauses = self.where_clauses_for(opaque_ty_id.0, bound_vars);
+
+        let identity_substs = InternalSubsts::identity_for_item(self.interner.tcx, opaque_ty_id.0);
+
+        let explicit_item_bounds = self.interner.tcx.bound_explicit_item_bounds(opaque_ty_id.0);
+        let bounds =
+            explicit_item_bounds
+                .0
+                .iter()
+                .map(|(bound, _)| {
+                    explicit_item_bounds.rebind(*bound).subst(self.interner.tcx, &bound_vars)
+                })
+                .map(|bound| {
+                    bound.fold_with(&mut ReplaceOpaqueTyFolder {
+                        tcx: self.interner.tcx,
+                        opaque_ty_id,
+                        identity_substs,
+                        binder_index: ty::INNERMOST,
+                    })
+                })
+                .filter_map(|bound| {
+                    LowerInto::<
+                    Option<chalk_ir::QuantifiedWhereClause<RustInterner<'tcx>>>
+                >::lower_into(bound, self.interner)
+                })
+                .collect();
+
+        // Binder for the bound variable representing the concrete impl Trait type.
+        let existential_binder = chalk_ir::VariableKinds::from1(
+            self.interner,
+            chalk_ir::VariableKind::Ty(chalk_ir::TyVariableKind::General),
+        );
+
+        let value = chalk_solve::rust_ir::OpaqueTyDatumBound {
+            bounds: chalk_ir::Binders::new(existential_binder.clone(), bounds),
+            where_clauses: chalk_ir::Binders::new(existential_binder, where_clauses),
+        };
+
+        let binders = binders_for(self.interner, bound_vars);
+        Arc::new(chalk_solve::rust_ir::OpaqueTyDatum {
+            opaque_ty_id,
+            bound: chalk_ir::Binders::new(binders, value),
+        })
+    }
+
+    fn program_clauses_for_env(
+        &self,
+        environment: &chalk_ir::Environment<RustInterner<'tcx>>,
+    ) -> chalk_ir::ProgramClauses<RustInterner<'tcx>> {
+        chalk_solve::program_clauses_for_env(self, environment)
+    }
+
+    fn well_known_trait_id(
+        &self,
+        well_known_trait: chalk_solve::rust_ir::WellKnownTrait,
+    ) -> Option<chalk_ir::TraitId<RustInterner<'tcx>>> {
+        use chalk_solve::rust_ir::WellKnownTrait::*;
+        let lang_items = self.interner.tcx.lang_items();
+        let def_id = match well_known_trait {
+            Sized => lang_items.sized_trait(),
+            Copy => lang_items.copy_trait(),
+            Clone => lang_items.clone_trait(),
+            Drop => lang_items.drop_trait(),
+            Fn => lang_items.fn_trait(),
+            FnMut => lang_items.fn_mut_trait(),
+            FnOnce => lang_items.fn_once_trait(),
+            Generator => lang_items.gen_trait(),
+            Unsize => lang_items.unsize_trait(),
+            Unpin => lang_items.unpin_trait(),
+            CoerceUnsized => lang_items.coerce_unsized_trait(),
+            DiscriminantKind => lang_items.discriminant_kind_trait(),
+            DispatchFromDyn => lang_items.dispatch_from_dyn_trait(),
+        };
+        def_id.map(chalk_ir::TraitId)
+    }
+
+    fn is_object_safe(&self, trait_id: chalk_ir::TraitId<RustInterner<'tcx>>) -> bool {
+        self.interner.tcx.is_object_safe(trait_id.0)
+    }
+
+    fn hidden_opaque_type(
+        &self,
+        _id: chalk_ir::OpaqueTyId<RustInterner<'tcx>>,
+    ) -> chalk_ir::Ty<RustInterner<'tcx>> {
+        // FIXME(chalk): actually get hidden ty
+        self.interner
+            .tcx
+            .mk_ty(ty::Tuple(self.interner.tcx.intern_type_list(&[])))
+            .lower_into(self.interner)
+    }
+
+    fn closure_kind(
+        &self,
+        _closure_id: chalk_ir::ClosureId<RustInterner<'tcx>>,
+        substs: &chalk_ir::Substitution<RustInterner<'tcx>>,
+    ) -> chalk_solve::rust_ir::ClosureKind {
+        let kind = &substs.as_slice(self.interner)[substs.len(self.interner) - 3];
+        match kind.assert_ty_ref(self.interner).kind(self.interner) {
+            chalk_ir::TyKind::Scalar(chalk_ir::Scalar::Int(int_ty)) => match int_ty {
+                chalk_ir::IntTy::I8 => chalk_solve::rust_ir::ClosureKind::Fn,
+                chalk_ir::IntTy::I16 => chalk_solve::rust_ir::ClosureKind::FnMut,
+                chalk_ir::IntTy::I32 => chalk_solve::rust_ir::ClosureKind::FnOnce,
+                _ => bug!("bad closure kind"),
+            },
+            _ => bug!("bad closure kind"),
+        }
+    }
+
+    fn closure_inputs_and_output(
+        &self,
+        _closure_id: chalk_ir::ClosureId<RustInterner<'tcx>>,
+        substs: &chalk_ir::Substitution<RustInterner<'tcx>>,
+    ) -> chalk_ir::Binders<chalk_solve::rust_ir::FnDefInputsAndOutputDatum<RustInterner<'tcx>>>
+    {
+        let sig = &substs.as_slice(self.interner)[substs.len(self.interner) - 2];
+        match sig.assert_ty_ref(self.interner).kind(self.interner) {
+            chalk_ir::TyKind::Function(f) => {
+                let substitution = f.substitution.0.as_slice(self.interner);
+                let return_type = substitution.last().unwrap().assert_ty_ref(self.interner).clone();
+                // Closure arguments are tupled
+                let argument_tuple = substitution[0].assert_ty_ref(self.interner);
+                let argument_types = match argument_tuple.kind(self.interner) {
+                    chalk_ir::TyKind::Tuple(_len, substitution) => substitution
+                        .iter(self.interner)
+                        .map(|arg| arg.assert_ty_ref(self.interner))
+                        .cloned()
+                        .collect(),
+                    _ => bug!("Expecting closure FnSig args to be tupled."),
+                };
+
+                chalk_ir::Binders::new(
+                    chalk_ir::VariableKinds::from_iter(
+                        self.interner,
+                        (0..f.num_binders).map(|_| chalk_ir::VariableKind::Lifetime),
+                    ),
+                    chalk_solve::rust_ir::FnDefInputsAndOutputDatum { argument_types, return_type },
+                )
+            }
+            _ => panic!("Invalid sig."),
+        }
+    }
+
+    fn closure_upvars(
+        &self,
+        _closure_id: chalk_ir::ClosureId<RustInterner<'tcx>>,
+        substs: &chalk_ir::Substitution<RustInterner<'tcx>>,
+    ) -> chalk_ir::Binders<chalk_ir::Ty<RustInterner<'tcx>>> {
+        let inputs_and_output = self.closure_inputs_and_output(_closure_id, substs);
+        let tuple = substs.as_slice(self.interner).last().unwrap().assert_ty_ref(self.interner);
+        inputs_and_output.map_ref(|_| tuple.clone())
+    }
+
+    fn closure_fn_substitution(
+        &self,
+        _closure_id: chalk_ir::ClosureId<RustInterner<'tcx>>,
+        substs: &chalk_ir::Substitution<RustInterner<'tcx>>,
+    ) -> chalk_ir::Substitution<RustInterner<'tcx>> {
+        let substitution = &substs.as_slice(self.interner)[0..substs.len(self.interner) - 3];
+        chalk_ir::Substitution::from_iter(self.interner, substitution)
+    }
+
+    fn generator_datum(
+        &self,
+        _generator_id: chalk_ir::GeneratorId<RustInterner<'tcx>>,
+    ) -> Arc<chalk_solve::rust_ir::GeneratorDatum<RustInterner<'tcx>>> {
+        unimplemented!()
+    }
+
+    fn generator_witness_datum(
+        &self,
+        _generator_id: chalk_ir::GeneratorId<RustInterner<'tcx>>,
+    ) -> Arc<chalk_solve::rust_ir::GeneratorWitnessDatum<RustInterner<'tcx>>> {
+        unimplemented!()
+    }
+
+    fn unification_database(&self) -> &dyn chalk_ir::UnificationDatabase<RustInterner<'tcx>> {
+        self
+    }
+
+    fn discriminant_type(
+        &self,
+        _: chalk_ir::Ty<RustInterner<'tcx>>,
+    ) -> chalk_ir::Ty<RustInterner<'tcx>> {
+        unimplemented!()
+    }
+}
+
+impl<'tcx> chalk_ir::UnificationDatabase<RustInterner<'tcx>> for RustIrDatabase<'tcx> {
+    fn fn_def_variance(
+        &self,
+        def_id: chalk_ir::FnDefId<RustInterner<'tcx>>,
+    ) -> chalk_ir::Variances<RustInterner<'tcx>> {
+        let variances = self.interner.tcx.variances_of(def_id.0);
+        chalk_ir::Variances::from_iter(
+            self.interner,
+            variances.iter().map(|v| v.lower_into(self.interner)),
+        )
+    }
+
+    fn adt_variance(
+        &self,
+        adt_id: chalk_ir::AdtId<RustInterner<'tcx>>,
+    ) -> chalk_ir::Variances<RustInterner<'tcx>> {
+        let variances = self.interner.tcx.variances_of(adt_id.0.did());
+        chalk_ir::Variances::from_iter(
+            self.interner,
+            variances.iter().map(|v| v.lower_into(self.interner)),
+        )
+    }
+}
+
+/// Creates an `InternalSubsts` that maps each generic parameter to a higher-ranked
+/// var bound at index `0`. For types, we use a `BoundVar` index equal to
+/// the type parameter index. For regions, we use the `BoundRegionKind::BrNamed`
+/// variant (which has a `DefId`).
+fn bound_vars_for_item<'tcx>(tcx: TyCtxt<'tcx>, def_id: DefId) -> SubstsRef<'tcx> {
+    InternalSubsts::for_item(tcx, def_id, |param, substs| match param.kind {
+        ty::GenericParamDefKind::Type { .. } => tcx
+            .mk_ty(ty::Bound(
+                ty::INNERMOST,
+                ty::BoundTy {
+                    var: ty::BoundVar::from(param.index),
+                    kind: ty::BoundTyKind::Param(param.name),
+                },
+            ))
+            .into(),
+
+        ty::GenericParamDefKind::Lifetime => {
+            let br = ty::BoundRegion {
+                var: ty::BoundVar::from_usize(substs.len()),
+                kind: ty::BrAnon(substs.len() as u32),
+            };
+            tcx.mk_region(ty::ReLateBound(ty::INNERMOST, br)).into()
+        }
+
+        ty::GenericParamDefKind::Const { .. } => tcx
+            .mk_const(ty::ConstS {
+                kind: ty::ConstKind::Bound(ty::INNERMOST, ty::BoundVar::from(param.index)),
+                ty: tcx.type_of(param.def_id),
+            })
+            .into(),
+    })
+}
+
+fn binders_for<'tcx>(
+    interner: RustInterner<'tcx>,
+    bound_vars: SubstsRef<'tcx>,
+) -> chalk_ir::VariableKinds<RustInterner<'tcx>> {
+    chalk_ir::VariableKinds::from_iter(
+        interner,
+        bound_vars.iter().map(|arg| match arg.unpack() {
+            ty::subst::GenericArgKind::Lifetime(_re) => chalk_ir::VariableKind::Lifetime,
+            ty::subst::GenericArgKind::Type(_ty) => {
+                chalk_ir::VariableKind::Ty(chalk_ir::TyVariableKind::General)
+            }
+            ty::subst::GenericArgKind::Const(c) => {
+                chalk_ir::VariableKind::Const(c.ty().lower_into(interner))
+            }
+        }),
+    )
+}
+
+struct ReplaceOpaqueTyFolder<'tcx> {
+    tcx: TyCtxt<'tcx>,
+    opaque_ty_id: chalk_ir::OpaqueTyId<RustInterner<'tcx>>,
+    identity_substs: SubstsRef<'tcx>,
+    binder_index: ty::DebruijnIndex,
+}
+
+impl<'tcx> ty::TypeFolder<'tcx> for ReplaceOpaqueTyFolder<'tcx> {
+    fn tcx<'b>(&'b self) -> TyCtxt<'tcx> {
+        self.tcx
+    }
+
+    fn fold_binder<T: TypeFoldable<'tcx>>(
+        &mut self,
+        t: ty::Binder<'tcx, T>,
+    ) -> ty::Binder<'tcx, T> {
+        self.binder_index.shift_in(1);
+        let t = t.super_fold_with(self);
+        self.binder_index.shift_out(1);
+        t
+    }
+
+    fn fold_ty(&mut self, ty: Ty<'tcx>) -> Ty<'tcx> {
+        if let ty::Opaque(def_id, substs) = *ty.kind() {
+            if def_id == self.opaque_ty_id.0 && substs == self.identity_substs {
+                return self.tcx.mk_ty(ty::Bound(
+                    self.binder_index,
+                    ty::BoundTy::from(ty::BoundVar::from_u32(0)),
+                ));
+            }
+        }
+        ty
+    }
+}
diff --git a/compiler/rustc_traits/src/chalk/lowering.rs b/compiler/rustc_traits/src/chalk/lowering.rs
new file mode 100644
index 000000000..c7c604e14
--- /dev/null
+++ b/compiler/rustc_traits/src/chalk/lowering.rs
@@ -0,0 +1,1172 @@
+//! 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, SubstsRef<'tcx>> for &chalk_ir::Substitution<RustInterner<'tcx>> {
+    fn lower_into(self, interner: RustInterner<'tcx>) -> SubstsRef<'tcx> {
+        interner.tcx.mk_substs(self.iter(interner).map(|subst| subst.lower_into(interner)))
+    }
+}
+
+impl<'tcx> LowerInto<'tcx, chalk_ir::AliasTy<RustInterner<'tcx>>> for ty::ProjectionTy<'tcx> {
+    fn lower_into(self, interner: RustInterner<'tcx>) -> chalk_ir::AliasTy<RustInterner<'tcx>> {
+        chalk_ir::AliasTy::Projection(chalk_ir::ProjectionTy {
+            associated_ty_id: chalk_ir::AssocTypeId(self.item_def_id),
+            substitution: self.substs.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::Trait(predicate) => chalk_ir::DomainGoal::FromEnv(
+                    chalk_ir::FromEnv::Trait(predicate.trait_ref.lower_into(interner)),
+                ),
+                ty::PredicateKind::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::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::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::ClosureKind(..)
+                | ty::PredicateKind::Subtype(..)
+                | ty::PredicateKind::Coerce(..)
+                | ty::PredicateKind::ConstEvaluatable(..)
+                | 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::Trait(predicate) => {
+                chalk_ir::GoalData::DomainGoal(chalk_ir::DomainGoal::Holds(
+                    chalk_ir::WhereClause::Implemented(predicate.trait_ref.lower_into(interner)),
+                ))
+            }
+            ty::PredicateKind::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::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::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!("unexpect 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::Coerce(..)
+            | ty::PredicateKind::ConstEvaluatable(..)
+            | 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: self.projection_ty.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)
+                        }),
+                    )),
+                })
+            }
+            ty::Dynamic(predicates, region) => 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::Never => chalk_ir::TyKind::Never,
+            ty::Tuple(types) => {
+                chalk_ir::TyKind::Tuple(types.len(), types.as_substs().lower_into(interner))
+            }
+            ty::Projection(proj) => chalk_ir::TyKind::Alias(proj.lower_into(interner)),
+            ty::Opaque(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.name.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(..) => unimplemented!(),
+            TyKind::GeneratorWitness(..) => unimplemented!(),
+            TyKind::Never => ty::Never,
+            TyKind::Tuple(_len, substitution) => {
+                ty::Tuple(substitution.lower_into(interner).try_as_type_list().unwrap())
+            }
+            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::Opaque(opaque_ty.0, substitution.lower_into(interner))
+            }
+            TyKind::AssociatedType(assoc_ty, substitution) => ty::Projection(ty::ProjectionTy {
+                substs: substitution.lower_into(interner),
+                item_def_id: assoc_ty.0,
+            }),
+            TyKind::Foreign(def_id) => ty::Foreign(def_id.0),
+            TyKind::Error => return interner.tcx.ty_error(),
+            TyKind::Placeholder(placeholder) => ty::Placeholder(ty::Placeholder {
+                universe: ty::UniverseIndex::from_usize(placeholder.ui.counter),
+                name: ty::BoundVar::from_usize(placeholder.idx),
+            }),
+            TyKind::Alias(alias_ty) => match alias_ty {
+                chalk_ir::AliasTy::Projection(projection) => ty::Projection(ty::ProjectionTy {
+                    item_def_id: projection.associated_ty_id.0,
+                    substs: projection.substitution.lower_into(interner),
+                }),
+                chalk_ir::AliasTy::Opaque(opaque) => {
+                    ty::Opaque(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::InferenceVar(_, _) => unimplemented!(),
+            TyKind::Dyn(_) => unimplemented!(),
+        };
+        interner.tcx.mk_ty(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::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,
+                })
+                .intern(interner)
+            }
+            ty::ReEmpty(ui) => {
+                chalk_ir::LifetimeData::Empty(chalk_ir::UniverseIndex { counter: ui.index() })
+                    .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 kind = match self.data(interner) {
+            chalk_ir::LifetimeData::BoundVar(var) => ty::ReLateBound(
+                ty::DebruijnIndex::from_u32(var.debruijn.depth()),
+                ty::BoundRegion {
+                    var: ty::BoundVar::from_usize(var.index),
+                    kind: ty::BrAnon(var.index as u32),
+                },
+            ),
+            chalk_ir::LifetimeData::InferenceVar(_var) => unimplemented!(),
+            chalk_ir::LifetimeData::Placeholder(p) => ty::RePlaceholder(ty::Placeholder {
+                universe: ty::UniverseIndex::from_usize(p.ui.counter),
+                name: ty::BoundRegionKind::BrAnon(p.idx as u32),
+            }),
+            chalk_ir::LifetimeData::Static => return interner.tcx.lifetimes.re_static,
+            chalk_ir::LifetimeData::Empty(ui) => {
+                ty::ReEmpty(ty::UniverseIndex::from_usize(ui.counter))
+            }
+            chalk_ir::LifetimeData::Erased => return interner.tcx.lifetimes.re_erased,
+            chalk_ir::LifetimeData::Phantom(void, _) => match *void {},
+        };
+        interner.tcx.mk_region(kind)
+    }
+}
+
+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(ty::ConstS { ty, kind })
+    }
+}
+
+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::Trait(predicate) => {
+                Some(chalk_ir::WhereClause::Implemented(predicate.trait_ref.lower_into(interner)))
+            }
+            ty::PredicateKind::RegionOutlives(predicate) => {
+                Some(chalk_ir::WhereClause::LifetimeOutlives(chalk_ir::LifetimeOutlives {
+                    a: predicate.0.lower_into(interner),
+                    b: predicate.1.lower_into(interner),
+                }))
+            }
+            ty::PredicateKind::TypeOutlives(predicate) => {
+                Some(chalk_ir::WhereClause::TypeOutlives(chalk_ir::TypeOutlives {
+                    ty: predicate.0.lower_into(interner),
+                    lifetime: predicate.1.lower_into(interner),
+                }))
+            }
+            ty::PredicateKind::Projection(predicate) => {
+                Some(chalk_ir::WhereClause::AliasEq(predicate.lower_into(interner)))
+            }
+            ty::PredicateKind::WellFormed(_ty) => None,
+
+            ty::PredicateKind::ObjectSafe(..)
+            | ty::PredicateKind::ClosureKind(..)
+            | ty::PredicateKind::Subtype(..)
+            | ty::PredicateKind::Coerce(..)
+            | ty::PredicateKind::ConstEvaluatable(..)
+            | ty::PredicateKind::ConstEquate(..)
+            | 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::Binder<'tcx, ty::ExistentialPredicate<'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_ty(ty::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.item_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::Trait(predicate) => Some(chalk_ir::Binders::new(
+                binders,
+                chalk_solve::rust_ir::InlineBound::TraitBound(
+                    predicate.trait_ref.lower_into(interner),
+                ),
+            )),
+            ty::PredicateKind::Projection(predicate) => Some(chalk_ir::Binders::new(
+                binders,
+                chalk_solve::rust_ir::InlineBound::AliasEqBound(predicate.lower_into(interner)),
+            )),
+            ty::PredicateKind::TypeOutlives(_predicate) => None,
+            ty::PredicateKind::WellFormed(_ty) => None,
+
+            ty::PredicateKind::RegionOutlives(..)
+            | ty::PredicateKind::ObjectSafe(..)
+            | ty::PredicateKind::ClosureKind(..)
+            | ty::PredicateKind::Subtype(..)
+            | ty::PredicateKind::Coerce(..)
+            | ty::PredicateKind::ConstEvaluatable(..)
+            | ty::PredicateKind::ConstEquate(..)
+            | 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.item_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<'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_iter().map(|(_, v)| v));
+
+    (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<'tcx> for BoundVarsCollector<'tcx> {
+    fn visit_binder<T: TypeVisitable<'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(var) => match self.parameters.entry(var) {
+                    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!();
+            }
+
+            _ => (),
+        };
+
+        r.super_visit_with(self)
+    }
+}
+
+/// 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<'tcx> for NamedBoundVarSubstitutor<'a, 'tcx> {
+    fn tcx<'b>(&'b self) -> TyCtxt<'tcx> {
+        self.tcx
+    }
+
+    fn fold_binder<T: TypeFoldable<'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(idx) => {
+                        let new_br = ty::BoundRegion { var: br.var, kind: ty::BrAnon(*idx) };
+                        return self.tcx.mk_region(ty::ReLateBound(index, new_br));
+                    }
+                    None => panic!("Missing `BrNamed`."),
+                },
+                ty::BrEnv => unimplemented!(),
+                ty::BrAnon(_) => {}
+            },
+            _ => (),
+        };
+
+        r.super_fold_with(self)
+    }
+}
+
+/// 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<usize, 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<'tcx> for ParamsSubstitutor<'tcx> {
+    fn tcx<'b>(&'b self) -> TyCtxt<'tcx> {
+        self.tcx
+    }
+
+    fn fold_binder<T: TypeFoldable<'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_ty(ty::Placeholder(ty::PlaceholderType {
+                    universe: ty::UniverseIndex::from_usize(0),
+                    name: ty::BoundVar::from_usize(idx),
+                })),
+                None => {
+                    self.list.push(param);
+                    let idx = self.list.len() - 1 + self.next_ty_placeholder;
+                    self.params.insert(idx, param);
+                    self.tcx.mk_ty(ty::Placeholder(ty::PlaceholderType {
+                        universe: ty::UniverseIndex::from_usize(0),
+                        name: ty::BoundVar::from_usize(idx),
+                    }))
+                }
+            },
+            _ => 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(*idx),
+                    };
+                    self.tcx.mk_region(ty::ReLateBound(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(idx) };
+                    self.named_regions.insert(_re.def_id, idx);
+                    self.tcx.mk_region(ty::ReLateBound(self.binder_index, br))
+                }
+            },
+
+            _ => r.super_fold_with(self),
+        }
+    }
+}
+
+pub(crate) struct ReverseParamsSubstitutor<'tcx> {
+    tcx: TyCtxt<'tcx>,
+    params: rustc_data_structures::fx::FxHashMap<usize, rustc_middle::ty::ParamTy>,
+}
+
+impl<'tcx> ReverseParamsSubstitutor<'tcx> {
+    pub(crate) fn new(
+        tcx: TyCtxt<'tcx>,
+        params: rustc_data_structures::fx::FxHashMap<usize, rustc_middle::ty::ParamTy>,
+    ) -> Self {
+        Self { tcx, params }
+    }
+}
+
+impl<'tcx> TypeFolder<'tcx> for ReverseParamsSubstitutor<'tcx> {
+    fn tcx<'b>(&'b 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, name }) => {
+                match self.params.get(&name.as_usize()) {
+                    Some(param) => self.tcx.mk_ty(ty::Param(*param)),
+                    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<'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.name.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(anon) = p.name {
+                    self.next_anon_region_placeholder = self.next_anon_region_placeholder.max(anon);
+                }
+            }
+
+            _ => (),
+        };
+
+        r.super_visit_with(self)
+    }
+}
diff --git a/compiler/rustc_traits/src/chalk/mod.rs b/compiler/rustc_traits/src/chalk/mod.rs
new file mode 100644
index 000000000..f76386fa7
--- /dev/null
+++ b/compiler/rustc_traits/src/chalk/mod.rs
@@ -0,0 +1,176 @@
+//! Calls `chalk-solve` to solve a `ty::Predicate`
+//!
+//! In order to call `chalk-solve`, this file must convert a `CanonicalChalkEnvironmentAndGoal` into
+//! a Chalk uncanonical goal. It then calls Chalk, and converts the answer back into rustc solution.
+
+pub(crate) mod db;
+pub(crate) mod lowering;
+
+use rustc_data_structures::fx::FxHashMap;
+
+use rustc_index::vec::IndexVec;
+
+use rustc_middle::infer::canonical::{CanonicalTyVarKind, CanonicalVarKind};
+use rustc_middle::traits::ChalkRustInterner;
+use rustc_middle::ty::query::Providers;
+use rustc_middle::ty::subst::GenericArg;
+use rustc_middle::ty::{self, BoundVar, ParamTy, TyCtxt, TypeFoldable, TypeVisitable};
+
+use rustc_infer::infer::canonical::{
+    Canonical, CanonicalVarValues, Certainty, QueryRegionConstraints, QueryResponse,
+};
+use rustc_infer::traits::{self, CanonicalChalkEnvironmentAndGoal};
+
+use crate::chalk::db::RustIrDatabase as ChalkRustIrDatabase;
+use crate::chalk::lowering::LowerInto;
+use crate::chalk::lowering::{ParamsSubstitutor, PlaceholdersCollector, ReverseParamsSubstitutor};
+
+use chalk_solve::Solution;
+
+pub(crate) fn provide(p: &mut Providers) {
+    *p = Providers { evaluate_goal, ..*p };
+}
+
+pub(crate) fn evaluate_goal<'tcx>(
+    tcx: TyCtxt<'tcx>,
+    obligation: CanonicalChalkEnvironmentAndGoal<'tcx>,
+) -> Result<&'tcx Canonical<'tcx, QueryResponse<'tcx, ()>>, traits::query::NoSolution> {
+    let interner = ChalkRustInterner { tcx };
+
+    // Chalk doesn't have a notion of `Params`, so instead we use placeholders.
+    let mut placeholders_collector = PlaceholdersCollector::new();
+    obligation.visit_with(&mut placeholders_collector);
+
+    let mut params_substitutor =
+        ParamsSubstitutor::new(tcx, placeholders_collector.next_ty_placeholder);
+    let obligation = obligation.fold_with(&mut params_substitutor);
+    let params: FxHashMap<usize, ParamTy> = params_substitutor.params;
+
+    let max_universe = obligation.max_universe.index();
+
+    let lowered_goal: chalk_ir::UCanonical<
+        chalk_ir::InEnvironment<chalk_ir::Goal<ChalkRustInterner<'tcx>>>,
+    > = chalk_ir::UCanonical {
+        canonical: chalk_ir::Canonical {
+            binders: chalk_ir::CanonicalVarKinds::from_iter(
+                interner,
+                obligation.variables.iter().map(|v| match v.kind {
+                    CanonicalVarKind::PlaceholderTy(_ty) => unimplemented!(),
+                    CanonicalVarKind::PlaceholderRegion(_ui) => unimplemented!(),
+                    CanonicalVarKind::Ty(ty) => match ty {
+                        CanonicalTyVarKind::General(ui) => chalk_ir::WithKind::new(
+                            chalk_ir::VariableKind::Ty(chalk_ir::TyVariableKind::General),
+                            chalk_ir::UniverseIndex { counter: ui.index() },
+                        ),
+                        CanonicalTyVarKind::Int => chalk_ir::WithKind::new(
+                            chalk_ir::VariableKind::Ty(chalk_ir::TyVariableKind::Integer),
+                            chalk_ir::UniverseIndex::root(),
+                        ),
+                        CanonicalTyVarKind::Float => chalk_ir::WithKind::new(
+                            chalk_ir::VariableKind::Ty(chalk_ir::TyVariableKind::Float),
+                            chalk_ir::UniverseIndex::root(),
+                        ),
+                    },
+                    CanonicalVarKind::Region(ui) => chalk_ir::WithKind::new(
+                        chalk_ir::VariableKind::Lifetime,
+                        chalk_ir::UniverseIndex { counter: ui.index() },
+                    ),
+                    CanonicalVarKind::Const(_ui, _ty) => unimplemented!(),
+                    CanonicalVarKind::PlaceholderConst(_pc, _ty) => unimplemented!(),
+                }),
+            ),
+            value: obligation.value.lower_into(interner),
+        },
+        universes: max_universe + 1,
+    };
+
+    use chalk_solve::Solver;
+    let mut solver = chalk_engine::solve::SLGSolver::new(32, None);
+    let db = ChalkRustIrDatabase { interner };
+    debug!(?lowered_goal);
+    let solution = solver.solve(&db, &lowered_goal);
+    debug!(?obligation, ?solution, "evaluate goal");
+
+    // Ideally, the code to convert *back* to rustc types would live close to
+    // the code to convert *from* rustc types. Right now though, we don't
+    // really need this and so it's really minimal.
+    // Right now, we also treat a `Unique` solution the same as
+    // `Ambig(Definite)`. This really isn't right.
+    let make_solution = |subst: chalk_ir::Substitution<_>,
+                         binders: chalk_ir::CanonicalVarKinds<_>| {
+        use rustc_middle::infer::canonical::CanonicalVarInfo;
+
+        let mut var_values: IndexVec<BoundVar, GenericArg<'tcx>> = IndexVec::new();
+        let mut reverse_param_substitutor = ReverseParamsSubstitutor::new(tcx, params);
+        subst.as_slice(interner).iter().for_each(|p| {
+            var_values.push(p.lower_into(interner).fold_with(&mut reverse_param_substitutor));
+        });
+        let variables: Vec<_> = binders
+            .iter(interner)
+            .map(|var| {
+                let kind = match var.kind {
+                    chalk_ir::VariableKind::Ty(ty_kind) => CanonicalVarKind::Ty(match ty_kind {
+                        chalk_ir::TyVariableKind::General => CanonicalTyVarKind::General(
+                            ty::UniverseIndex::from_usize(var.skip_kind().counter),
+                        ),
+                        chalk_ir::TyVariableKind::Integer => CanonicalTyVarKind::Int,
+                        chalk_ir::TyVariableKind::Float => CanonicalTyVarKind::Float,
+                    }),
+                    chalk_ir::VariableKind::Lifetime => CanonicalVarKind::Region(
+                        ty::UniverseIndex::from_usize(var.skip_kind().counter),
+                    ),
+                    // FIXME(compiler-errors): We don't currently have a way of turning
+                    // a Chalk ty back into a rustc ty, right?
+                    chalk_ir::VariableKind::Const(_) => todo!(),
+                };
+                CanonicalVarInfo { kind }
+            })
+            .collect();
+        let max_universe = binders.iter(interner).map(|v| v.skip_kind().counter).max().unwrap_or(0);
+        let sol = Canonical {
+            max_universe: ty::UniverseIndex::from_usize(max_universe),
+            variables: tcx.intern_canonical_var_infos(&variables),
+            value: QueryResponse {
+                var_values: CanonicalVarValues { var_values },
+                region_constraints: QueryRegionConstraints::default(),
+                certainty: Certainty::Proven,
+                opaque_types: vec![],
+                value: (),
+            },
+        };
+        tcx.arena.alloc(sol)
+    };
+    solution
+        .map(|s| match s {
+            Solution::Unique(subst) => {
+                // FIXME(chalk): handle constraints
+                make_solution(subst.value.subst, subst.binders)
+            }
+            Solution::Ambig(guidance) => {
+                match guidance {
+                    chalk_solve::Guidance::Definite(subst) => {
+                        make_solution(subst.value, subst.binders)
+                    }
+                    chalk_solve::Guidance::Suggested(_) => unimplemented!(),
+                    chalk_solve::Guidance::Unknown => {
+                        // chalk_fulfill doesn't use the var_values here, so
+                        // let's just ignore that
+                        let sol = Canonical {
+                            max_universe: ty::UniverseIndex::from_usize(0),
+                            variables: obligation.variables,
+                            value: QueryResponse {
+                                var_values: CanonicalVarValues { var_values: IndexVec::new() }
+                                    .make_identity(tcx),
+                                region_constraints: QueryRegionConstraints::default(),
+                                certainty: Certainty::Ambiguous,
+                                opaque_types: vec![],
+                                value: (),
+                            },
+                        };
+                        &*tcx.arena.alloc(sol)
+                    }
+                }
+            }
+        })
+        .ok_or(traits::query::NoSolution)
+}