18 files changed, 526 insertions, 386 deletions

diff --git a/crates/hir_ty/src/autoderef.rs b/crates/hir_ty/src/autoderef.rs
index f8e9db9ae..71bc436e6 100644
--- a/crates/hir_ty/src/autoderef.rs
+++ b/crates/hir_ty/src/autoderef.rs
@@ -6,14 +6,15 @@
 use std::iter::successors;
 
 use base_db::CrateId;
-use chalk_ir::cast::Cast;
+use chalk_ir::{cast::Cast, fold::Fold, interner::HasInterner, VariableKind};
 use hir_def::lang_item::LangItemTarget;
 use hir_expand::name::name;
 use log::{info, warn};
 
 use crate::{
-    db::HirDatabase, AliasEq, AliasTy, BoundVar, Canonical, CanonicalVarKinds, DebruijnIndex,
-    InEnvironment, Interner, ProjectionTyExt, Solution, Ty, TyBuilder, TyKind,
+    db::HirDatabase, static_lifetime, AliasEq, AliasTy, BoundVar, Canonical, CanonicalVarKinds,
+    DebruijnIndex, InEnvironment, Interner, ProjectionTyExt, Solution, Substitution, Ty, TyBuilder,
+    TyKind,
 };
 
 const AUTODEREF_RECURSION_LIMIT: usize = 10;
@@ -103,7 +104,7 @@ fn deref_by_trait(
         binders: CanonicalVarKinds::from_iter(
             &Interner,
             ty.goal.binders.iter(&Interner).cloned().chain(Some(chalk_ir::WithKind::new(
-                chalk_ir::VariableKind::Ty(chalk_ir::TyVariableKind::General),
+                VariableKind::Ty(chalk_ir::TyVariableKind::General),
                 chalk_ir::UniverseIndex::ROOT,
             ))),
         ),
@@ -136,7 +137,9 @@ fn deref_by_trait(
                     return None;
                 }
             }
-            Some(Canonical {
+            // FIXME: we remove lifetime variables here since they can confuse
+            // the method resolution code later
+            Some(fixup_lifetime_variables(Canonical {
                 value: vars
                     .value
                     .subst
@@ -144,7 +147,7 @@ fn deref_by_trait(
                     .assert_ty_ref(&Interner)
                     .clone(),
                 binders: vars.binders.clone(),
-            })
+            }))
         }
         Solution::Ambig(_) => {
             info!("Ambiguous solution for derefing {:?}: {:?}", ty.goal, solution);
@@ -152,3 +155,32 @@ fn deref_by_trait(
         }
     }
 }
+
+fn fixup_lifetime_variables<T: Fold<Interner, Result = T> + HasInterner<Interner = Interner>>(
+    c: Canonical<T>,
+) -> Canonical<T> {
+    // Removes lifetime variables from the Canonical, replacing them by static lifetimes.
+    let mut i = 0;
+    let subst = Substitution::from_iter(
+        &Interner,
+        c.binders.iter(&Interner).map(|vk| match vk.kind {
+            VariableKind::Ty(_) => {
+                let index = i;
+                i += 1;
+                BoundVar::new(DebruijnIndex::INNERMOST, index).to_ty(&Interner).cast(&Interner)
+            }
+            VariableKind::Lifetime => static_lifetime().cast(&Interner),
+            VariableKind::Const(_) => unimplemented!(),
+        }),
+    );
+    let binders = CanonicalVarKinds::from_iter(
+        &Interner,
+        c.binders.iter(&Interner).filter(|vk| match vk.kind {
+            VariableKind::Ty(_) => true,
+            VariableKind::Lifetime => false,
+            VariableKind::Const(_) => true,
+        }),
+    );
+    let value = subst.apply(c.value, &Interner);
+    Canonical { binders, value }
+}
diff --git a/crates/hir_ty/src/chalk_cast.rs b/crates/hir_ty/src/chalk_cast.rs
deleted file mode 100644
index f27dee3fd..000000000
--- a/crates/hir_ty/src/chalk_cast.rs
+++ /dev/null
@@ -1,16 +0,0 @@
-//! Implementations of the Chalk `Cast` trait for our types.
-
-use chalk_ir::interner::HasInterner;
-
-use crate::{CallableSig, ReturnTypeImplTraits};
-
-macro_rules! has_interner {
-    ($t:ty) => {
-        impl HasInterner for $t {
-            type Interner = crate::Interner;
-        }
-    };
-}
-
-has_interner!(CallableSig);
-has_interner!(ReturnTypeImplTraits);
diff --git a/crates/hir_ty/src/traits/chalk.rs b/crates/hir_ty/src/chalk_db.rs
index b8c390b2e..8f054d06b 100644
--- a/crates/hir_ty/src/traits/chalk.rs
+++ b/crates/hir_ty/src/chalk_db.rs
@@ -1,50 +1,47 @@
-//! Conversion code from/to Chalk.
+//! The implementation of `RustIrDatabase` for Chalk, which provides information
+//! about the code that Chalk needs.
 use std::sync::Arc;
 
 use log::debug;
 
-use chalk_ir::{fold::shift::Shift, CanonicalVarKinds};
+use chalk_ir::{cast::Cast, fold::shift::Shift, CanonicalVarKinds};
 use chalk_solve::rust_ir::{self, OpaqueTyDatumBound, WellKnownTrait};
 
-use base_db::{salsa::InternKey, CrateId};
+use base_db::CrateId;
 use hir_def::{
     lang_item::{lang_attr, LangItemTarget},
-    AssocContainerId, AssocItemId, HasModule, Lookup, TypeAliasId,
+    AssocContainerId, AssocItemId, GenericDefId, HasModule, Lookup, TypeAliasId,
 };
 use hir_expand::name::name;
 
-use super::ChalkContext;
 use crate::{
     db::HirDatabase,
     display::HirDisplay,
-    from_assoc_type_id, make_only_type_binders,
+    from_assoc_type_id, from_chalk_trait_id, make_only_type_binders,
+    mapping::{from_chalk, ToChalk, TypeAliasAsValue},
     method_resolution::{TyFingerprint, ALL_FLOAT_FPS, ALL_INT_FPS},
     to_assoc_type_id, to_chalk_trait_id,
+    traits::ChalkContext,
     utils::generics,
-    AliasEq, AliasTy, BoundVar, CallableDefId, DebruijnIndex, FnDefId, ProjectionTy, Substitution,
-    TraitRef, TraitRefExt, Ty, TyBuilder, TyExt, TyKind, WhereClause,
+    AliasEq, AliasTy, BoundVar, CallableDefId, DebruijnIndex, FnDefId, Interner, ProjectionTy,
+    ProjectionTyExt, QuantifiedWhereClause, Substitution, TraitRef, TraitRefExt, Ty, TyBuilder,
+    TyExt, TyKind, WhereClause,
 };
-use mapping::{convert_where_clauses, generic_predicate_to_inline_bound, TypeAliasAsValue};
 
-pub use self::interner::Interner;
-pub(crate) use self::interner::*;
-
-pub(super) mod tls;
-mod interner;
-mod mapping;
-
-pub(crate) trait ToChalk {
-    type Chalk;
-    fn to_chalk(self, db: &dyn HirDatabase) -> Self::Chalk;
-    fn from_chalk(db: &dyn HirDatabase, chalk: Self::Chalk) -> Self;
-}
-
-pub(crate) fn from_chalk<T, ChalkT>(db: &dyn HirDatabase, chalk: ChalkT) -> T
-where
-    T: ToChalk<Chalk = ChalkT>,
-{
-    T::from_chalk(db, chalk)
-}
+pub(crate) type AssociatedTyDatum = chalk_solve::rust_ir::AssociatedTyDatum<Interner>;
+pub(crate) type TraitDatum = chalk_solve::rust_ir::TraitDatum<Interner>;
+pub(crate) type StructDatum = chalk_solve::rust_ir::AdtDatum<Interner>;
+pub(crate) type ImplDatum = chalk_solve::rust_ir::ImplDatum<Interner>;
+pub(crate) type OpaqueTyDatum = chalk_solve::rust_ir::OpaqueTyDatum<Interner>;
+
+pub(crate) type AssocTypeId = chalk_ir::AssocTypeId<Interner>;
+pub(crate) type TraitId = chalk_ir::TraitId<Interner>;
+pub(crate) type AdtId = chalk_ir::AdtId<Interner>;
+pub(crate) type ImplId = chalk_ir::ImplId<Interner>;
+pub(crate) type AssociatedTyValueId = chalk_solve::rust_ir::AssociatedTyValueId<Interner>;
+pub(crate) type AssociatedTyValue = chalk_solve::rust_ir::AssociatedTyValue<Interner>;
+pub(crate) type FnDefDatum = chalk_solve::rust_ir::FnDefDatum<Interner>;
+pub(crate) type Variances = chalk_ir::Variances<Interner>;
 
 impl<'a> chalk_solve::RustIrDatabase<Interner> for ChalkContext<'a> {
     fn associated_ty_data(&self, id: AssocTypeId) -> Arc<AssociatedTyDatum> {
@@ -82,7 +79,7 @@ impl<'a> chalk_solve::RustIrDatabase<Interner> for ChalkContext<'a> {
         binders: &CanonicalVarKinds<Interner>,
     ) -> Vec<ImplId> {
         debug!("impls_for_trait {:?}", trait_id);
-        let trait_: hir_def::TraitId = from_chalk(self.db, trait_id);
+        let trait_: hir_def::TraitId = from_chalk_trait_id(trait_id);
 
         let ty: Ty = parameters[0].assert_ty_ref(&Interner).clone();
 
@@ -101,7 +98,7 @@ impl<'a> chalk_solve::RustIrDatabase<Interner> for ChalkContext<'a> {
             None
         }
 
-        let self_ty_fp = TyFingerprint::for_impl(&ty);
+        let self_ty_fp = TyFingerprint::for_trait_impl(&ty);
         let fps: &[TyFingerprint] = match binder_kind(&ty, binders) {
             Some(chalk_ir::TyVariableKind::Integer) => &ALL_INT_FPS,
             Some(chalk_ir::TyVariableKind::Float) => &ALL_FLOAT_FPS,
@@ -164,7 +161,7 @@ impl<'a> chalk_solve::RustIrDatabase<Interner> for ChalkContext<'a> {
             Some(LangItemTarget::TraitId(trait_)) => trait_,
             _ => return None,
         };
-        Some(trait_.to_chalk(self.db))
+        Some(to_chalk_trait_id(trait_))
     }
 
     fn program_clauses_for_env(
@@ -311,7 +308,7 @@ impl<'a> chalk_solve::RustIrDatabase<Interner> for ChalkContext<'a> {
     }
 
     fn trait_name(&self, trait_id: chalk_ir::TraitId<Interner>) -> String {
-        let id = from_chalk(self.db, trait_id);
+        let id = from_chalk_trait_id(trait_id);
         self.db.trait_data(id).name.to_string()
     }
     fn adt_name(&self, chalk_ir::AdtId(adt_id): AdtId) -> String {
@@ -416,7 +413,7 @@ pub(crate) fn trait_datum_query(
     trait_id: TraitId,
 ) -> Arc<TraitDatum> {
     debug!("trait_datum {:?}", trait_id);
-    let trait_: hir_def::TraitId = from_chalk(db, trait_id);
+    let trait_ = from_chalk_trait_id(trait_id);
     let trait_data = db.trait_data(trait_);
     debug!("trait {:?} = {:?}", trait_id, trait_data.name);
     let generic_params = generics(db.upcast(), trait_.into());
@@ -679,38 +676,65 @@ pub(crate) fn adt_variance_query(
     )
 }
 
-impl From<FnDefId> for crate::db::InternedCallableDefId {
-    fn from(fn_def_id: FnDefId) -> Self {
-        InternKey::from_intern_id(fn_def_id.0)
-    }
-}
-
-impl From<crate::db::InternedCallableDefId> for FnDefId {
-    fn from(callable_def_id: crate::db::InternedCallableDefId) -> Self {
-        chalk_ir::FnDefId(callable_def_id.as_intern_id())
-    }
-}
-
-impl From<OpaqueTyId> for crate::db::InternedOpaqueTyId {
-    fn from(id: OpaqueTyId) -> Self {
-        InternKey::from_intern_id(id.0)
-    }
-}
-
-impl From<crate::db::InternedOpaqueTyId> for OpaqueTyId {
-    fn from(id: crate::db::InternedOpaqueTyId) -> Self {
-        chalk_ir::OpaqueTyId(id.as_intern_id())
-    }
-}
-
-impl From<chalk_ir::ClosureId<Interner>> for crate::db::InternedClosureId {
-    fn from(id: chalk_ir::ClosureId<Interner>) -> Self {
-        Self::from_intern_id(id.0)
-    }
+pub(super) fn convert_where_clauses(
+    db: &dyn HirDatabase,
+    def: GenericDefId,
+    substs: &Substitution,
+) -> Vec<chalk_ir::QuantifiedWhereClause<Interner>> {
+    let generic_predicates = db.generic_predicates(def);
+    let mut result = Vec::with_capacity(generic_predicates.len());
+    for pred in generic_predicates.iter() {
+        result.push(pred.clone().substitute(&Interner, substs));
+    }
+    result
 }
 
-impl From<crate::db::InternedClosureId> for chalk_ir::ClosureId<Interner> {
-    fn from(id: crate::db::InternedClosureId) -> Self {
-        chalk_ir::ClosureId(id.as_intern_id())
+pub(super) fn generic_predicate_to_inline_bound(
+    db: &dyn HirDatabase,
+    pred: &QuantifiedWhereClause,
+    self_ty: &Ty,
+) -> Option<chalk_ir::Binders<rust_ir::InlineBound<Interner>>> {
+    // An InlineBound is like a GenericPredicate, except the self type is left out.
+    // We don't have a special type for this, but Chalk does.
+    let self_ty_shifted_in = self_ty.clone().shifted_in_from(&Interner, DebruijnIndex::ONE);
+    let (pred, binders) = pred.as_ref().into_value_and_skipped_binders();
+    match pred {
+        WhereClause::Implemented(trait_ref) => {
+            if trait_ref.self_type_parameter(&Interner) != self_ty_shifted_in {
+                // we can only convert predicates back to type bounds if they
+                // have the expected self type
+                return None;
+            }
+            let args_no_self = trait_ref.substitution.as_slice(&Interner)[1..]
+                .iter()
+                .map(|ty| ty.clone().cast(&Interner))
+                .collect();
+            let trait_bound = rust_ir::TraitBound { trait_id: trait_ref.trait_id, args_no_self };
+            Some(chalk_ir::Binders::new(binders, rust_ir::InlineBound::TraitBound(trait_bound)))
+        }
+        WhereClause::AliasEq(AliasEq { alias: AliasTy::Projection(projection_ty), ty }) => {
+            if projection_ty.self_type_parameter(&Interner) != self_ty_shifted_in {
+                return None;
+            }
+            let trait_ = projection_ty.trait_(db);
+            let args_no_self = projection_ty.substitution.as_slice(&Interner)[1..]
+                .iter()
+                .map(|ty| ty.clone().cast(&Interner))
+                .collect();
+            let alias_eq_bound = rust_ir::AliasEqBound {
+                value: ty.clone(),
+                trait_bound: rust_ir::TraitBound {
+                    trait_id: to_chalk_trait_id(trait_),
+                    args_no_self,
+                },
+                associated_ty_id: projection_ty.associated_ty_id,
+                parameters: Vec::new(), // FIXME we don't support generic associated types yet
+            };
+            Some(chalk_ir::Binders::new(
+                binders,
+                rust_ir::InlineBound::AliasEqBound(alias_eq_bound),
+            ))
+        }
+        _ => None,
     }
 }
diff --git a/crates/hir_ty/src/db.rs b/crates/hir_ty/src/db.rs
index 326c20240..1690926ad 100644
--- a/crates/hir_ty/src/db.rs
+++ b/crates/hir_ty/src/db.rs
@@ -1,4 +1,5 @@
-//! FIXME: write short doc here
+//! The home of `HirDatabase`, which is the Salsa database containing all the
+//! type inference-related queries.
 
 use std::sync::Arc;
 
@@ -10,9 +11,9 @@ use hir_def::{
 use la_arena::ArenaMap;
 
 use crate::{
+    chalk_db,
     method_resolution::{InherentImpls, TraitImpls},
-    traits::chalk,
-    Binders, CallableDefId, FnDefId, ImplTraitId, InferenceResult, PolyFnSig,
+    Binders, CallableDefId, FnDefId, ImplTraitId, InferenceResult, Interner, PolyFnSig,
     QuantifiedWhereClause, ReturnTypeImplTraits, TraitRef, Ty, TyDefId, ValueTyDefId,
 };
 use hir_expand::name::Name;
@@ -94,33 +95,38 @@ pub trait HirDatabase: DefDatabase + Upcast<dyn DefDatabase> {
     #[salsa::interned]
     fn intern_closure(&self, id: (DefWithBodyId, ExprId)) -> InternedClosureId;
 
-    #[salsa::invoke(chalk::associated_ty_data_query)]
-    fn associated_ty_data(&self, id: chalk::AssocTypeId) -> Arc<chalk::AssociatedTyDatum>;
+    #[salsa::invoke(chalk_db::associated_ty_data_query)]
+    fn associated_ty_data(&self, id: chalk_db::AssocTypeId) -> Arc<chalk_db::AssociatedTyDatum>;
 
-    #[salsa::invoke(chalk::trait_datum_query)]
-    fn trait_datum(&self, krate: CrateId, trait_id: chalk::TraitId) -> Arc<chalk::TraitDatum>;
+    #[salsa::invoke(chalk_db::trait_datum_query)]
+    fn trait_datum(&self, krate: CrateId, trait_id: chalk_db::TraitId)
+        -> Arc<chalk_db::TraitDatum>;
 
-    #[salsa::invoke(chalk::struct_datum_query)]
-    fn struct_datum(&self, krate: CrateId, struct_id: chalk::AdtId) -> Arc<chalk::StructDatum>;
+    #[salsa::invoke(chalk_db::struct_datum_query)]
+    fn struct_datum(
+        &self,
+        krate: CrateId,
+        struct_id: chalk_db::AdtId,
+    ) -> Arc<chalk_db::StructDatum>;
 
-    #[salsa::invoke(crate::traits::chalk::impl_datum_query)]
-    fn impl_datum(&self, krate: CrateId, impl_id: chalk::ImplId) -> Arc<chalk::ImplDatum>;
+    #[salsa::invoke(chalk_db::impl_datum_query)]
+    fn impl_datum(&self, krate: CrateId, impl_id: chalk_db::ImplId) -> Arc<chalk_db::ImplDatum>;
 
-    #[salsa::invoke(crate::traits::chalk::fn_def_datum_query)]
-    fn fn_def_datum(&self, krate: CrateId, fn_def_id: FnDefId) -> Arc<chalk::FnDefDatum>;
+    #[salsa::invoke(chalk_db::fn_def_datum_query)]
+    fn fn_def_datum(&self, krate: CrateId, fn_def_id: FnDefId) -> Arc<chalk_db::FnDefDatum>;
 
-    #[salsa::invoke(crate::traits::chalk::fn_def_variance_query)]
-    fn fn_def_variance(&self, krate: CrateId, fn_def_id: FnDefId) -> chalk::Variances;
+    #[salsa::invoke(chalk_db::fn_def_variance_query)]
+    fn fn_def_variance(&self, krate: CrateId, fn_def_id: FnDefId) -> chalk_db::Variances;
 
-    #[salsa::invoke(crate::traits::chalk::adt_variance_query)]
-    fn adt_variance(&self, krate: CrateId, adt_id: chalk::AdtId) -> chalk::Variances;
+    #[salsa::invoke(chalk_db::adt_variance_query)]
+    fn adt_variance(&self, krate: CrateId, adt_id: chalk_db::AdtId) -> chalk_db::Variances;
 
-    #[salsa::invoke(crate::traits::chalk::associated_ty_value_query)]
+    #[salsa::invoke(chalk_db::associated_ty_value_query)]
     fn associated_ty_value(
         &self,
         krate: CrateId,
-        id: chalk::AssociatedTyValueId,
-    ) -> Arc<chalk::AssociatedTyValue>;
+        id: chalk_db::AssociatedTyValueId,
+    ) -> Arc<chalk_db::AssociatedTyValue>;
 
     #[salsa::invoke(crate::traits::trait_solve_query)]
     fn trait_solve(
@@ -129,12 +135,12 @@ pub trait HirDatabase: DefDatabase + Upcast<dyn DefDatabase> {
         goal: crate::Canonical<crate::InEnvironment<crate::DomainGoal>>,
     ) -> Option<crate::Solution>;
 
-    #[salsa::invoke(crate::traits::chalk::program_clauses_for_chalk_env_query)]
+    #[salsa::invoke(chalk_db::program_clauses_for_chalk_env_query)]
     fn program_clauses_for_chalk_env(
         &self,
         krate: CrateId,
-        env: chalk_ir::Environment<chalk::Interner>,
-    ) -> chalk_ir::ProgramClauses<chalk::Interner>;
+        env: chalk_ir::Environment<Interner>,
+    ) -> chalk_ir::ProgramClauses<Interner>;
 }
 
 fn infer_wait(db: &dyn HirDatabase, def: DefWithBodyId) -> Arc<InferenceResult> {
diff --git a/crates/hir_ty/src/diagnostics.rs b/crates/hir_ty/src/diagnostics.rs
index 86f937e1d..84fc8ce14 100644
--- a/crates/hir_ty/src/diagnostics.rs
+++ b/crates/hir_ty/src/diagnostics.rs
@@ -1,4 +1,4 @@
-//! FIXME: write short doc here
+//! Type inference-based diagnostics.
 mod expr;
 mod match_check;
 mod unsafe_check;
diff --git a/crates/hir_ty/src/display.rs b/crates/hir_ty/src/display.rs
index 92224b46b..e7c9dabc2 100644
--- a/crates/hir_ty/src/display.rs
+++ b/crates/hir_ty/src/display.rs
@@ -1,4 +1,6 @@
-//! FIXME: write short doc here
+//! The `HirDisplay` trait, which serves two purposes: Turning various bits from
+//! HIR back into source code, and just displaying them for debugging/testing
+//! purposes.
 
 use std::{
     array,
@@ -20,11 +22,11 @@ use hir_expand::name::Name;
 
 use crate::{
     const_from_placeholder_idx, db::HirDatabase, from_assoc_type_id, from_foreign_def_id,
-    from_placeholder_idx, lt_from_placeholder_idx, primitive, subst_prefix, to_assoc_type_id,
-    traits::chalk::from_chalk, utils::generics, AdtId, AliasEq, AliasTy, CallableDefId,
-    CallableSig, Const, ConstValue, DomainGoal, GenericArg, ImplTraitId, Interner, Lifetime,
-    LifetimeData, LifetimeOutlives, Mutability, OpaqueTy, ProjectionTy, ProjectionTyExt,
-    QuantifiedWhereClause, Scalar, TraitRef, TraitRefExt, Ty, TyExt, TyKind, WhereClause,
+    from_placeholder_idx, lt_from_placeholder_idx, mapping::from_chalk, primitive, subst_prefix,
+    to_assoc_type_id, utils::generics, AdtId, AliasEq, AliasTy, CallableDefId, CallableSig, Const,
+    ConstValue, DomainGoal, GenericArg, ImplTraitId, Interner, Lifetime, LifetimeData,
+    LifetimeOutlives, Mutability, OpaqueTy, ProjectionTy, ProjectionTyExt, QuantifiedWhereClause,
+    Scalar, TraitRef, TraitRefExt, Ty, TyExt, TyKind, WhereClause,
 };
 
 pub struct HirFormatter<'a> {
diff --git a/crates/hir_ty/src/infer/expr.rs b/crates/hir_ty/src/infer/expr.rs
index 7961f4a52..50497eecb 100644
--- a/crates/hir_ty/src/infer/expr.rs
+++ b/crates/hir_ty/src/infer/expr.rs
@@ -17,10 +17,11 @@ use syntax::ast::RangeOp;
 use crate::{
     autoderef, dummy_usize_const,
     lower::lower_to_chalk_mutability,
+    mapping::from_chalk,
     method_resolution, op,
     primitive::{self, UintTy},
     static_lifetime, to_chalk_trait_id,
-    traits::{chalk::from_chalk, FnTrait},
+    traits::FnTrait,
     utils::{generics, Generics},
     AdtId, Binders, CallableDefId, FnPointer, FnSig, FnSubst, InEnvironment, Interner,
     ProjectionTyExt, Rawness, Scalar, Substitution, TraitRef, Ty, TyBuilder, TyExt, TyKind,
diff --git a/crates/hir_ty/src/traits/chalk/interner.rs b/crates/hir_ty/src/interner.rs
index b6a3cec6d..a1656115d 100644
--- a/crates/hir_ty/src/traits/chalk/interner.rs
+++ b/crates/hir_ty/src/interner.rs
@@ -1,8 +1,7 @@
 //! Implementation of the Chalk `Interner` trait, which allows customizing the
 //! representation of the various objects Chalk deals with (types, goals etc.).
 
-use super::tls;
-use crate::GenericArg;
+use crate::{chalk_db, tls, GenericArg};
 use base_db::salsa::InternId;
 use chalk_ir::{Goal, GoalData};
 use hir_def::{
@@ -15,21 +14,6 @@ use std::{fmt, sync::Arc};
 #[derive(Debug, Copy, Clone, Hash, PartialOrd, Ord, PartialEq, Eq)]
 pub struct Interner;
 
-pub(crate) type AssocTypeId = chalk_ir::AssocTypeId<Interner>;
-pub(crate) type AssociatedTyDatum = chalk_solve::rust_ir::AssociatedTyDatum<Interner>;
-pub(crate) type TraitId = chalk_ir::TraitId<Interner>;
-pub(crate) type TraitDatum = chalk_solve::rust_ir::TraitDatum<Interner>;
-pub(crate) type AdtId = chalk_ir::AdtId<Interner>;
-pub(crate) type StructDatum = chalk_solve::rust_ir::AdtDatum<Interner>;
-pub(crate) type ImplId = chalk_ir::ImplId<Interner>;
-pub(crate) type ImplDatum = chalk_solve::rust_ir::ImplDatum<Interner>;
-pub(crate) type AssociatedTyValueId = chalk_solve::rust_ir::AssociatedTyValueId<Interner>;
-pub(crate) type AssociatedTyValue = chalk_solve::rust_ir::AssociatedTyValue<Interner>;
-pub(crate) type FnDefDatum = chalk_solve::rust_ir::FnDefDatum<Interner>;
-pub(crate) type OpaqueTyId = chalk_ir::OpaqueTyId<Interner>;
-pub(crate) type OpaqueTyDatum = chalk_solve::rust_ir::OpaqueTyDatum<Interner>;
-pub(crate) type Variances = chalk_ir::Variances<Interner>;
-
 #[derive(PartialEq, Eq, Hash, Debug)]
 pub struct InternedWrapper<T>(T);
 
@@ -76,15 +60,24 @@ impl chalk_ir::interner::Interner for Interner {
     type Identifier = TypeAliasId;
     type FnAbi = ();
 
-    fn debug_adt_id(type_kind_id: AdtId, fmt: &mut fmt::Formatter<'_>) -> Option<fmt::Result> {
+    fn debug_adt_id(
+        type_kind_id: chalk_db::AdtId,
+        fmt: &mut fmt::Formatter<'_>,
+    ) -> Option<fmt::Result> {
         tls::with_current_program(|prog| Some(prog?.debug_struct_id(type_kind_id, fmt)))
     }
 
-    fn debug_trait_id(type_kind_id: TraitId, fmt: &mut fmt::Formatter<'_>) -> Option<fmt::Result> {
+    fn debug_trait_id(
+        type_kind_id: chalk_db::TraitId,
+        fmt: &mut fmt::Formatter<'_>,
+    ) -> Option<fmt::Result> {
         tls::with_current_program(|prog| Some(prog?.debug_trait_id(type_kind_id, fmt)))
     }
 
-    fn debug_assoc_type_id(id: AssocTypeId, fmt: &mut fmt::Formatter<'_>) -> Option<fmt::Result> {
+    fn debug_assoc_type_id(
+        id: chalk_db::AssocTypeId,
+        fmt: &mut fmt::Formatter<'_>,
+    ) -> Option<fmt::Result> {
         tls::with_current_program(|prog| Some(prog?.debug_assoc_type_id(id, fmt)))
     }
 
@@ -419,3 +412,12 @@ impl chalk_ir::interner::Interner for Interner {
 impl chalk_ir::interner::HasInterner for Interner {
     type Interner = Self;
 }
+
+#[macro_export]
+macro_rules! has_interner {
+    ($t:ty) => {
+        impl HasInterner for $t {
+            type Interner = crate::Interner;
+        }
+    };
+}
diff --git a/crates/hir_ty/src/lib.rs b/crates/hir_ty/src/lib.rs
index beb58d711..113234fa4 100644
--- a/crates/hir_ty/src/lib.rs
+++ b/crates/hir_ty/src/lib.rs
@@ -7,21 +7,23 @@ macro_rules! eprintln {
 }
 
 mod autoderef;
-pub mod primitive;
-pub mod traits;
-pub mod method_resolution;
-mod op;
-mod lower;
-pub(crate) mod infer;
-pub(crate) mod utils;
-mod chalk_cast;
-mod chalk_ext;
 mod builder;
+mod chalk_db;
+mod chalk_ext;
+mod infer;
+mod interner;
+mod lower;
+mod mapping;
+mod op;
+mod tls;
+mod utils;
 mod walk;
-
-pub mod display;
 pub mod db;
 pub mod diagnostics;
+pub mod display;
+pub mod method_resolution;
+pub mod primitive;
+pub mod traits;
 
 #[cfg(test)]
 mod tests;
@@ -30,16 +32,12 @@ mod test_db;
 
 use std::sync::Arc;
 
-use base_db::salsa;
 use chalk_ir::{
     fold::{Fold, Shift},
     interner::HasInterner,
     UintTy,
 };
-use hir_def::{
-    expr::ExprId, type_ref::Rawness, ConstParamId, LifetimeParamId, TraitId, TypeAliasId,
-    TypeParamId,
-};
+use hir_def::{expr::ExprId, type_ref::Rawness, TypeParamId};
 
 use crate::{db::HirDatabase, display::HirDisplay, utils::generics};
 
@@ -47,11 +45,17 @@ pub use autoderef::autoderef;
 pub use builder::TyBuilder;
 pub use chalk_ext::*;
 pub use infer::{could_unify, InferenceResult};
+pub use interner::Interner;
 pub use lower::{
     associated_type_shorthand_candidates, callable_item_sig, CallableDefId, ImplTraitLoweringMode,
     TyDefId, TyLoweringContext, ValueTyDefId,
 };
-pub use traits::{chalk::Interner, TraitEnvironment};
+pub use mapping::{
+    const_from_placeholder_idx, from_assoc_type_id, from_chalk_trait_id, from_foreign_def_id,
+    from_placeholder_idx, lt_from_placeholder_idx, to_assoc_type_id, to_chalk_trait_id,
+    to_foreign_def_id, to_placeholder_idx,
+};
+pub use traits::TraitEnvironment;
 pub use walk::TypeWalk;
 
 pub use chalk_ir::{
@@ -94,6 +98,10 @@ pub type ConstValue = chalk_ir::ConstValue<Interner>;
 pub type ConcreteConst = chalk_ir::ConcreteConst<Interner>;
 
 pub type ChalkTraitId = chalk_ir::TraitId<Interner>;
+pub type TraitRef = chalk_ir::TraitRef<Interner>;
+pub type QuantifiedWhereClause = Binders<WhereClause>;
+pub type QuantifiedWhereClauses = chalk_ir::QuantifiedWhereClauses<Interner>;
+pub type Canonical<T> = chalk_ir::Canonical<T>;
 
 pub type FnSig = chalk_ir::FnSig<Interner>;
 
@@ -118,14 +126,14 @@ pub fn param_idx(db: &dyn HirDatabase, id: TypeParamId) -> Option<usize> {
     generics(db.upcast(), id.parent).param_idx(id)
 }
 
-pub fn wrap_empty_binders<T>(value: T) -> Binders<T>
+pub(crate) fn wrap_empty_binders<T>(value: T) -> Binders<T>
 where
     T: Fold<Interner, Result = T> + HasInterner<Interner = Interner>,
 {
     Binders::empty(&Interner, value.shifted_in_from(&Interner, DebruijnIndex::ONE))
 }
 
-pub fn make_only_type_binders<T: HasInterner<Interner = Interner>>(
+pub(crate) fn make_only_type_binders<T: HasInterner<Interner = Interner>>(
     num_vars: usize,
     value: T,
 ) -> Binders<T> {
@@ -153,14 +161,6 @@ pub fn make_canonical<T: HasInterner<Interner = Interner>>(
     Canonical { value, binders: chalk_ir::CanonicalVarKinds::from_iter(&Interner, kinds) }
 }
 
-pub type TraitRef = chalk_ir::TraitRef<Interner>;
-
-pub type QuantifiedWhereClause = Binders<WhereClause>;
-
-pub type QuantifiedWhereClauses = chalk_ir::QuantifiedWhereClauses<Interner>;
-
-pub type Canonical<T> = chalk_ir::Canonical<T>;
-
 /// A function signature as seen by type inference: Several parameter types and
 /// one return type.
 #[derive(Clone, PartialEq, Eq, Debug)]
@@ -169,6 +169,8 @@ pub struct CallableSig {
     is_varargs: bool,
 }
 
+has_interner!(CallableSig);
+
 /// A polymorphic function signature.
 pub type PolyFnSig = Binders<CallableSig>;
 
@@ -232,61 +234,13 @@ pub struct ReturnTypeImplTraits {
     pub(crate) impl_traits: Vec<ReturnTypeImplTrait>,
 }
 
+has_interner!(ReturnTypeImplTraits);
+
 #[derive(Clone, PartialEq, Eq, Debug, Hash)]
 pub(crate) struct ReturnTypeImplTrait {
     pub(crate) bounds: Binders<Vec<QuantifiedWhereClause>>,
 }
 
-pub fn to_foreign_def_id(id: TypeAliasId) -> ForeignDefId {
-    chalk_ir::ForeignDefId(salsa::InternKey::as_intern_id(&id))
-}
-
-pub fn from_foreign_def_id(id: ForeignDefId) -> TypeAliasId {
-    salsa::InternKey::from_intern_id(id.0)
-}
-
-pub fn to_assoc_type_id(id: TypeAliasId) -> AssocTypeId {
-    chalk_ir::AssocTypeId(salsa::InternKey::as_intern_id(&id))
-}
-
-pub fn from_assoc_type_id(id: AssocTypeId) -> TypeAliasId {
-    salsa::InternKey::from_intern_id(id.0)
-}
-
-pub fn from_placeholder_idx(db: &dyn HirDatabase, idx: PlaceholderIndex) -> TypeParamId {
-    assert_eq!(idx.ui, chalk_ir::UniverseIndex::ROOT);
-    let interned_id = salsa::InternKey::from_intern_id(salsa::InternId::from(idx.idx));
-    db.lookup_intern_type_param_id(interned_id)
-}
-
-pub fn to_placeholder_idx(db: &dyn HirDatabase, id: TypeParamId) -> PlaceholderIndex {
-    let interned_id = db.intern_type_param_id(id);
-    PlaceholderIndex {
-        ui: chalk_ir::UniverseIndex::ROOT,
-        idx: salsa::InternKey::as_intern_id(&interned_id).as_usize(),
-    }
-}
-
-pub fn lt_from_placeholder_idx(db: &dyn HirDatabase, idx: PlaceholderIndex) -> LifetimeParamId {
-    assert_eq!(idx.ui, chalk_ir::UniverseIndex::ROOT);
-    let interned_id = salsa::InternKey::from_intern_id(salsa::InternId::from(idx.idx));
-    db.lookup_intern_lifetime_param_id(interned_id)
-}
-
-pub fn const_from_placeholder_idx(db: &dyn HirDatabase, idx: PlaceholderIndex) -> ConstParamId {
-    assert_eq!(idx.ui, chalk_ir::UniverseIndex::ROOT);
-    let interned_id = salsa::InternKey::from_intern_id(salsa::InternId::from(idx.idx));
-    db.lookup_intern_const_param_id(interned_id)
-}
-
-pub fn to_chalk_trait_id(id: TraitId) -> ChalkTraitId {
-    chalk_ir::TraitId(salsa::InternKey::as_intern_id(&id))
-}
-
-pub fn from_chalk_trait_id(id: ChalkTraitId) -> TraitId {
-    salsa::InternKey::from_intern_id(id.0)
-}
-
 pub fn static_lifetime() -> Lifetime {
     LifetimeData::Static.intern(&Interner)
 }
diff --git a/crates/hir_ty/src/lower.rs b/crates/hir_ty/src/lower.rs
index 8a22d9ea3..a035686bc 100644
--- a/crates/hir_ty/src/lower.rs
+++ b/crates/hir_ty/src/lower.rs
@@ -27,13 +27,14 @@ use stdx::impl_from;
 
 use crate::{
     db::HirDatabase,
-    dummy_usize_const, static_lifetime, to_assoc_type_id, to_chalk_trait_id, to_placeholder_idx,
-    traits::chalk::{Interner, ToChalk},
+    dummy_usize_const,
+    mapping::ToChalk,
+    static_lifetime, to_assoc_type_id, to_chalk_trait_id, to_placeholder_idx,
     utils::{
         all_super_trait_refs, associated_type_by_name_including_super_traits, generics, Generics,
     },
     AliasEq, AliasTy, Binders, BoundVar, CallableSig, DebruijnIndex, DynTy, FnPointer, FnSig,
-    FnSubst, ImplTraitId, OpaqueTy, PolyFnSig, ProjectionTy, QuantifiedWhereClause,
+    FnSubst, ImplTraitId, Interner, OpaqueTy, PolyFnSig, ProjectionTy, QuantifiedWhereClause,
     QuantifiedWhereClauses, ReturnTypeImplTrait, ReturnTypeImplTraits, Substitution,
     TraitEnvironment, TraitRef, TraitRefExt, Ty, TyBuilder, TyKind, WhereClause,
 };
diff --git a/crates/hir_ty/src/mapping.rs b/crates/hir_ty/src/mapping.rs
new file mode 100644
index 000000000..5e86fafe5
--- /dev/null
+++ b/crates/hir_ty/src/mapping.rs
@@ -0,0 +1,154 @@
+//! This module contains the implementations of the `ToChalk` trait, which
+//! handles conversion between our data types and their corresponding types in
+//! Chalk (in both directions); plus some helper functions for more specialized
+//! conversions.
+
+use chalk_solve::rust_ir;
+
+use base_db::salsa::{self, InternKey};
+use hir_def::{ConstParamId, LifetimeParamId, TraitId, TypeAliasId, TypeParamId};
+
+use crate::{
+    chalk_db, db::HirDatabase, AssocTypeId, CallableDefId, ChalkTraitId, FnDefId, ForeignDefId,
+    Interner, OpaqueTyId, PlaceholderIndex,
+};
+
+pub(crate) trait ToChalk {
+    type Chalk;
+    fn to_chalk(self, db: &dyn HirDatabase) -> Self::Chalk;
+    fn from_chalk(db: &dyn HirDatabase, chalk: Self::Chalk) -> Self;
+}
+
+pub(crate) fn from_chalk<T, ChalkT>(db: &dyn HirDatabase, chalk: ChalkT) -> T
+where
+    T: ToChalk<Chalk = ChalkT>,
+{
+    T::from_chalk(db, chalk)
+}
+
+impl ToChalk for hir_def::ImplId {
+    type Chalk = chalk_db::ImplId;
+
+    fn to_chalk(self, _db: &dyn HirDatabase) -> chalk_db::ImplId {
+        chalk_ir::ImplId(self.as_intern_id())
+    }
+
+    fn from_chalk(_db: &dyn HirDatabase, impl_id: chalk_db::ImplId) -> hir_def::ImplId {
+        InternKey::from_intern_id(impl_id.0)
+    }
+}
+
+impl ToChalk for CallableDefId {
+    type Chalk = FnDefId;
+
+    fn to_chalk(self, db: &dyn HirDatabase) -> FnDefId {
+        db.intern_callable_def(self).into()
+    }
+
+    fn from_chalk(db: &dyn HirDatabase, fn_def_id: FnDefId) -> CallableDefId {
+        db.lookup_intern_callable_def(fn_def_id.into())
+    }
+}
+
+pub(crate) struct TypeAliasAsValue(pub(crate) TypeAliasId);
+
+impl ToChalk for TypeAliasAsValue {
+    type Chalk = chalk_db::AssociatedTyValueId;
+
+    fn to_chalk(self, _db: &dyn HirDatabase) -> chalk_db::AssociatedTyValueId {
+        rust_ir::AssociatedTyValueId(self.0.as_intern_id())
+    }
+
+    fn from_chalk(
+        _db: &dyn HirDatabase,
+        assoc_ty_value_id: chalk_db::AssociatedTyValueId,
+    ) -> TypeAliasAsValue {
+        TypeAliasAsValue(TypeAliasId::from_intern_id(assoc_ty_value_id.0))
+    }
+}
+
+impl From<FnDefId> for crate::db::InternedCallableDefId {
+    fn from(fn_def_id: FnDefId) -> Self {
+        InternKey::from_intern_id(fn_def_id.0)
+    }
+}
+
+impl From<crate::db::InternedCallableDefId> for FnDefId {
+    fn from(callable_def_id: crate::db::InternedCallableDefId) -> Self {
+        chalk_ir::FnDefId(callable_def_id.as_intern_id())
+    }
+}
+
+impl From<OpaqueTyId> for crate::db::InternedOpaqueTyId {
+    fn from(id: OpaqueTyId) -> Self {
+        InternKey::from_intern_id(id.0)
+    }
+}
+
+impl From<crate::db::InternedOpaqueTyId> for OpaqueTyId {
+    fn from(id: crate::db::InternedOpaqueTyId) -> Self {
+        chalk_ir::OpaqueTyId(id.as_intern_id())
+    }
+}
+
+impl From<chalk_ir::ClosureId<Interner>> for crate::db::InternedClosureId {
+    fn from(id: chalk_ir::ClosureId<Interner>) -> Self {
+        Self::from_intern_id(id.0)
+    }
+}
+
+impl From<crate::db::InternedClosureId> for chalk_ir::ClosureId<Interner> {
+    fn from(id: crate::db::InternedClosureId) -> Self {
+        chalk_ir::ClosureId(id.as_intern_id())
+    }
+}
+
+pub fn to_foreign_def_id(id: TypeAliasId) -> ForeignDefId {
+    chalk_ir::ForeignDefId(salsa::InternKey::as_intern_id(&id))
+}
+
+pub fn from_foreign_def_id(id: ForeignDefId) -> TypeAliasId {
+    salsa::InternKey::from_intern_id(id.0)
+}
+
+pub fn to_assoc_type_id(id: TypeAliasId) -> AssocTypeId {
+    chalk_ir::AssocTypeId(salsa::InternKey::as_intern_id(&id))
+}
+
+pub fn from_assoc_type_id(id: AssocTypeId) -> TypeAliasId {
+    salsa::InternKey::from_intern_id(id.0)
+}
+
+pub fn from_placeholder_idx(db: &dyn HirDatabase, idx: PlaceholderIndex) -> TypeParamId {
+    assert_eq!(idx.ui, chalk_ir::UniverseIndex::ROOT);
+    let interned_id = salsa::InternKey::from_intern_id(salsa::InternId::from(idx.idx));
+    db.lookup_intern_type_param_id(interned_id)
+}
+
+pub fn to_placeholder_idx(db: &dyn HirDatabase, id: TypeParamId) -> PlaceholderIndex {
+    let interned_id = db.intern_type_param_id(id);
+    PlaceholderIndex {
+        ui: chalk_ir::UniverseIndex::ROOT,
+        idx: salsa::InternKey::as_intern_id(&interned_id).as_usize(),
+    }
+}
+
+pub fn lt_from_placeholder_idx(db: &dyn HirDatabase, idx: PlaceholderIndex) -> LifetimeParamId {
+    assert_eq!(idx.ui, chalk_ir::UniverseIndex::ROOT);
+    let interned_id = salsa::InternKey::from_intern_id(salsa::InternId::from(idx.idx));
+    db.lookup_intern_lifetime_param_id(interned_id)
+}
+
+pub fn const_from_placeholder_idx(db: &dyn HirDatabase, idx: PlaceholderIndex) -> ConstParamId {
+    assert_eq!(idx.ui, chalk_ir::UniverseIndex::ROOT);
+    let interned_id = salsa::InternKey::from_intern_id(salsa::InternId::from(idx.idx));
+    db.lookup_intern_const_param_id(interned_id)
+}
+
+pub fn to_chalk_trait_id(id: TraitId) -> ChalkTraitId {
+    chalk_ir::TraitId(salsa::InternKey::as_intern_id(&id))
+}
+
+pub fn from_chalk_trait_id(id: ChalkTraitId) -> TraitId {
+    salsa::InternKey::from_intern_id(id.0)
+}
diff --git a/crates/hir_ty/src/method_resolution.rs b/crates/hir_ty/src/method_resolution.rs
index be3e4f09a..ece884241 100644
--- a/crates/hir_ty/src/method_resolution.rs
+++ b/crates/hir_ty/src/method_resolution.rs
@@ -13,6 +13,7 @@ use hir_def::{
 };
 use hir_expand::name::Name;
 use rustc_hash::{FxHashMap, FxHashSet};
+use stdx::always;
 
 use crate::{
     autoderef,
@@ -21,32 +22,36 @@ use crate::{
     primitive::{self, FloatTy, IntTy, UintTy},
     static_lifetime,
     utils::all_super_traits,
-    AdtId, Canonical, CanonicalVarKinds, DebruijnIndex, FnPointer, FnSig, ForeignDefId,
-    InEnvironment, Interner, Scalar, Substitution, TraitEnvironment, TraitRefExt, Ty, TyBuilder,
-    TyExt, TyKind,
+    AdtId, Canonical, CanonicalVarKinds, DebruijnIndex, ForeignDefId, InEnvironment, Interner,
+    Scalar, Substitution, TraitEnvironment, TraitRefExt, Ty, TyBuilder, TyExt, TyKind,
 };
 
 /// This is used as a key for indexing impls.
 #[derive(Debug, Copy, Clone, PartialEq, Eq, Hash)]
 pub enum TyFingerprint {
+    // These are lang item impls:
     Str,
     Slice,
     Array,
     Never,
     RawPtr(Mutability),
     Scalar(Scalar),
+    // These can have user-defined impls:
     Adt(hir_def::AdtId),
     Dyn(TraitId),
-    Tuple(usize),
     ForeignType(ForeignDefId),
-    FnPtr(usize, FnSig),
+    // These only exist for trait impls
+    Unit,
+    Unnameable,
+    Function(u32),
 }
 
 impl TyFingerprint {
-    /// Creates a TyFingerprint for looking up an impl. Only certain types can
-    /// have impls: if we have some `struct S`, we can have an `impl S`, but not
-    /// `impl &S`. Hence, this will return `None` for reference types and such.
-    pub fn for_impl(ty: &Ty) -> Option<TyFingerprint> {
+    /// Creates a TyFingerprint for looking up an inherent impl. Only certain
+    /// types can have inherent impls: if we have some `struct S`, we can have
+    /// an `impl S`, but not `impl &S`. Hence, this will return `None` for
+    /// reference types and such.
+    pub fn for_inherent_impl(ty: &Ty) -> Option<TyFingerprint> {
         let fp = match ty.kind(&Interner) {
             TyKind::Str => TyFingerprint::Str,
             TyKind::Never => TyFingerprint::Never,
@@ -54,17 +59,52 @@ impl TyFingerprint {
             TyKind::Array(..) => TyFingerprint::Array,
             TyKind::Scalar(scalar) => TyFingerprint::Scalar(*scalar),
             TyKind::Adt(AdtId(adt), _) => TyFingerprint::Adt(*adt),
-            TyKind::Tuple(cardinality, _) => TyFingerprint::Tuple(*cardinality),
             TyKind::Raw(mutability, ..) => TyFingerprint::RawPtr(*mutability),
             TyKind::Foreign(alias_id, ..) => TyFingerprint::ForeignType(*alias_id),
-            TyKind::Function(FnPointer { sig, substitution: substs, .. }) => {
-                TyFingerprint::FnPtr(substs.0.len(&Interner) - 1, *sig)
-            }
             TyKind::Dyn(_) => ty.dyn_trait().map(|trait_| TyFingerprint::Dyn(trait_))?,
             _ => return None,
         };
         Some(fp)
     }
+
+    /// Creates a TyFingerprint for looking up a trait impl.
+    pub fn for_trait_impl(ty: &Ty) -> Option<TyFingerprint> {
+        let fp = match ty.kind(&Interner) {
+            TyKind::Str => TyFingerprint::Str,
+            TyKind::Never => TyFingerprint::Never,
+            TyKind::Slice(..) => TyFingerprint::Slice,
+            TyKind::Array(..) => TyFingerprint::Array,
+            TyKind::Scalar(scalar) => TyFingerprint::Scalar(*scalar),
+            TyKind::Adt(AdtId(adt), _) => TyFingerprint::Adt(*adt),
+            TyKind::Raw(mutability, ..) => TyFingerprint::RawPtr(*mutability),
+            TyKind::Foreign(alias_id, ..) => TyFingerprint::ForeignType(*alias_id),
+            TyKind::Dyn(_) => ty.dyn_trait().map(|trait_| TyFingerprint::Dyn(trait_))?,
+            TyKind::Ref(_, _, ty) => return TyFingerprint::for_trait_impl(ty),
+            TyKind::Tuple(_, subst) => {
+                let first_ty = subst.interned().get(0).map(|arg| arg.assert_ty_ref(&Interner));
+                if let Some(ty) = first_ty {
+                    return TyFingerprint::for_trait_impl(ty);
+                } else {
+                    TyFingerprint::Unit
+                }
+            }
+            TyKind::AssociatedType(_, _)
+            | TyKind::OpaqueType(_, _)
+            | TyKind::FnDef(_, _)
+            | TyKind::Closure(_, _)
+            | TyKind::Generator(..)
+            | TyKind::GeneratorWitness(..) => TyFingerprint::Unnameable,
+            TyKind::Function(fn_ptr) => {
+                TyFingerprint::Function(fn_ptr.substitution.0.len(&Interner) as u32)
+            }
+            TyKind::Alias(_)
+            | TyKind::Placeholder(_)
+            | TyKind::BoundVar(_)
+            | TyKind::InferenceVar(_, _)
+            | TyKind::Error => return None,
+        };
+        Some(fp)
+    }
 }
 
 pub(crate) const ALL_INT_FPS: [TyFingerprint; 12] = [
@@ -112,7 +152,7 @@ impl TraitImpls {
                         None => continue,
                     };
                     let self_ty = db.impl_self_ty(impl_id);
-                    let self_ty_fp = TyFingerprint::for_impl(self_ty.skip_binders());
+                    let self_ty_fp = TyFingerprint::for_trait_impl(self_ty.skip_binders());
                     impls
                         .map
                         .entry(target_trait)
@@ -157,10 +197,13 @@ impl TraitImpls {
     }
 
     /// Queries all trait impls for the given type.
-    pub fn for_self_ty(&self, fp: TyFingerprint) -> impl Iterator<Item = ImplId> + '_ {
+    pub fn for_self_ty_without_blanket_impls(
+        &self,
+        fp: TyFingerprint,
+    ) -> impl Iterator<Item = ImplId> + '_ {
         self.map
             .values()
-            .flat_map(move |impls| impls.get(&None).into_iter().chain(impls.get(&Some(fp))))
+            .flat_map(move |impls| impls.get(&Some(fp)).into_iter())
             .flat_map(|it| it.iter().copied())
     }
 
@@ -215,7 +258,9 @@ impl InherentImpls {
                 }
 
                 let self_ty = db.impl_self_ty(impl_id);
-                if let Some(fp) = TyFingerprint::for_impl(self_ty.skip_binders()) {
+                let fp = TyFingerprint::for_inherent_impl(self_ty.skip_binders());
+                always!(fp.is_some());
+                if let Some(fp) = fp {
                     map.entry(fp).or_default().push(impl_id);
                 }
             }
@@ -228,7 +273,7 @@ impl InherentImpls {
     }
 
     pub fn for_self_ty(&self, self_ty: &Ty) -> &[ImplId] {
-        match TyFingerprint::for_impl(self_ty) {
+        match TyFingerprint::for_inherent_impl(self_ty) {
             Some(fp) => self.map.get(&fp).map(|vec| vec.as_ref()).unwrap_or(&[]),
             None => &[],
         }
@@ -609,6 +654,7 @@ fn iterate_trait_method_candidates(
                 }
             }
             known_implemented = true;
+            // FIXME: we shouldn't be ignoring the binders here
             if callback(&self_ty.value, *item) {
                 return true;
             }
diff --git a/crates/hir_ty/src/primitive.rs b/crates/hir_ty/src/primitive.rs
index 2449addfb..d7f48c69a 100644
--- a/crates/hir_ty/src/primitive.rs
+++ b/crates/hir_ty/src/primitive.rs
@@ -1,7 +1,4 @@
-//! Defines primitive types, which have a couple of peculiarities:
-//!
-//! * during type inference, they can be uncertain (ie, `let x = 92;`)
-//! * they don't belong to any particular crate.
+//! A few helper functions for dealing with primitives.
 
 pub use chalk_ir::{FloatTy, IntTy, UintTy};
 pub use hir_def::builtin_type::{BuiltinFloat, BuiltinInt, BuiltinUint};
diff --git a/crates/hir_ty/src/tests/regression.rs b/crates/hir_ty/src/tests/regression.rs
index b69f86050..9cd9f473d 100644
--- a/crates/hir_ty/src/tests/regression.rs
+++ b/crates/hir_ty/src/tests/regression.rs
@@ -974,3 +974,41 @@ fn param_overrides_fn() {
         "#,
     )
 }
+
+#[test]
+fn lifetime_from_chalk_during_deref() {
+    check_types(
+        r#"
+        #[lang = "deref"]
+        pub trait Deref {
+            type Target;
+        }
+
+        struct Box<T: ?Sized> {}
+        impl<T> Deref for Box<T> {
+            type Target = T;
+
+            fn deref(&self) -> &Self::Target {
+                loop {}
+            }
+        }
+
+        trait Iterator {
+            type Item;
+        }
+
+        pub struct Iter<'a, T: 'a> {
+            inner: Box<dyn IterTrait<'a, T, Item = &'a T> + 'a>,
+        }
+
+        trait IterTrait<'a, T: 'a>: Iterator<Item = &'a T> {
+            fn clone_box(&self);
+        }
+
+        fn clone_iter<T>(s: Iter<T>) {
+            s.inner.clone_box();
+          //^^^^^^^^^^^^^^^^^^^ ()
+        }
+        "#,
+    )
+}
diff --git a/crates/hir_ty/src/tests/traits.rs b/crates/hir_ty/src/tests/traits.rs
index 65b71fdfa..1c1aa491d 100644
--- a/crates/hir_ty/src/tests/traits.rs
+++ b/crates/hir_ty/src/tests/traits.rs
@@ -3413,3 +3413,33 @@ fn foo() {
         "#]],
     );
 }
+
+#[test]
+fn renamed_extern_crate_in_block() {
+    check_types(
+        r#"
+//- /lib.rs crate:lib deps:serde
+use serde::Deserialize;
+
+struct Foo {}
+
+const _ : () = {
+    extern crate serde as _serde;
+    impl _serde::Deserialize for Foo {
+        fn deserialize() -> u8 { 0 }
+    }
+};
+
+fn foo() {
+    Foo::deserialize();
+  //^^^^^^^^^^^^^^^^^^ u8
+}
+
+//- /serde.rs crate:serde
+
+pub trait Deserialize {
+    fn deserialize() -> u8;
+}
+    "#,
+    );
+}
diff --git a/crates/hir_ty/src/traits/chalk/tls.rs b/crates/hir_ty/src/tls.rs
index 8892a63a9..87c671a42 100644
--- a/crates/hir_ty/src/traits/chalk/tls.rs
+++ b/crates/hir_ty/src/tls.rs
@@ -4,8 +4,10 @@ use std::fmt;
 use chalk_ir::{AliasTy, GenericArg, Goal, Goals, Lifetime, ProgramClauseImplication};
 use itertools::Itertools;
 
-use super::{from_chalk, Interner};
-use crate::{db::HirDatabase, from_assoc_type_id, CallableDefId};
+use crate::{
+    chalk_db, db::HirDatabase, from_assoc_type_id, from_chalk_trait_id, mapping::from_chalk,
+    CallableDefId, Interner,
+};
 use hir_def::{AdtId, AssocContainerId, Lookup, TypeAliasId};
 
 pub(crate) use unsafe_tls::{set_current_program, with_current_program};
@@ -15,7 +17,7 @@ pub(crate) struct DebugContext<'a>(&'a dyn HirDatabase);
 impl DebugContext<'_> {
     pub(crate) fn debug_struct_id(
         &self,
-        id: super::AdtId,
+        id: chalk_db::AdtId,
         f: &mut fmt::Formatter<'_>,
     ) -> Result<(), fmt::Error> {
         let name = match id.0 {
@@ -28,17 +30,17 @@ impl DebugContext<'_> {
 
     pub(crate) fn debug_trait_id(
         &self,
-        id: super::TraitId,
+        id: chalk_db::TraitId,
         fmt: &mut fmt::Formatter<'_>,
     ) -> Result<(), fmt::Error> {
-        let trait_: hir_def::TraitId = from_chalk(self.0, id);
+        let trait_: hir_def::TraitId = from_chalk_trait_id(id);
         let trait_data = self.0.trait_data(trait_);
         write!(fmt, "{}", trait_data.name)
     }
 
     pub(crate) fn debug_assoc_type_id(
         &self,
-        id: super::AssocTypeId,
+        id: chalk_db::AssocTypeId,
         fmt: &mut fmt::Formatter<'_>,
     ) -> Result<(), fmt::Error> {
         let type_alias: TypeAliasId = from_assoc_type_id(id);
diff --git a/crates/hir_ty/src/traits.rs b/crates/hir_ty/src/traits.rs
index 1cda72d22..9936d0803 100644
--- a/crates/hir_ty/src/traits.rs
+++ b/crates/hir_ty/src/traits.rs
@@ -1,28 +1,26 @@
 //! Trait solving using Chalk.
+
 use std::env::var;
 
-use base_db::CrateId;
 use chalk_ir::cast::Cast;
 use chalk_solve::{logging_db::LoggingRustIrDatabase, Solver};
+
+use base_db::CrateId;
 use hir_def::{lang_item::LangItemTarget, TraitId};
 use stdx::panic_context;
 
 use crate::{
     db::HirDatabase, AliasEq, AliasTy, Canonical, DomainGoal, Guidance, HirDisplay, InEnvironment,
-    Solution, TraitRefExt, Ty, TyKind, WhereClause,
+    Interner, Solution, TraitRefExt, Ty, TyKind, WhereClause,
 };
 
-use self::chalk::Interner;
-
-pub(crate) mod chalk;
-
 /// This controls how much 'time' we give the Chalk solver before giving up.
 const CHALK_SOLVER_FUEL: i32 = 100;
 
 #[derive(Debug, Copy, Clone)]
-struct ChalkContext<'a> {
-    db: &'a dyn HirDatabase,
-    krate: CrateId,
+pub(crate) struct ChalkContext<'a> {
+    pub(crate) db: &'a dyn HirDatabase,
+    pub(crate) krate: CrateId,
 }
 
 fn create_chalk_solver() -> chalk_recursive::RecursiveSolver<Interner> {
@@ -148,7 +146,7 @@ fn solve(
     // don't set the TLS for Chalk unless Chalk debugging is active, to make
     // extra sure we only use it for debugging
     let solution =
-        if is_chalk_debug() { chalk::tls::set_current_program(db, solve) } else { solve() };
+        if is_chalk_debug() { crate::tls::set_current_program(db, solve) } else { solve() };
 
     solution
 }
diff --git a/crates/hir_ty/src/traits/chalk/mapping.rs b/crates/hir_ty/src/traits/chalk/mapping.rs
deleted file mode 100644
index e78581ea5..000000000
--- a/crates/hir_ty/src/traits/chalk/mapping.rs
+++ /dev/null
@@ -1,131 +0,0 @@
-//! This module contains the implementations of the `ToChalk` trait, which
-//! handles conversion between our data types and their corresponding types in
-//! Chalk (in both directions); plus some helper functions for more specialized
-//! conversions.
-
-use chalk_ir::cast::Cast;
-use chalk_solve::rust_ir;
-
-use base_db::salsa::InternKey;
-use hir_def::{GenericDefId, TypeAliasId};
-
-use crate::{
-    db::HirDatabase, AliasTy, CallableDefId, ProjectionTyExt, QuantifiedWhereClause, Substitution,
-    Ty, WhereClause,
-};
-
-use super::interner::*;
-use super::*;
-
-impl ToChalk for hir_def::TraitId {
-    type Chalk = TraitId;
-
-    fn to_chalk(self, _db: &dyn HirDatabase) -> TraitId {
-        chalk_ir::TraitId(self.as_intern_id())
-    }
-
-    fn from_chalk(_db: &dyn HirDatabase, trait_id: TraitId) -> hir_def::TraitId {
-        InternKey::from_intern_id(trait_id.0)
-    }
-}
-
-impl ToChalk for hir_def::ImplId {
-    type Chalk = ImplId;
-
-    fn to_chalk(self, _db: &dyn HirDatabase) -> ImplId {
-        chalk_ir::ImplId(self.as_intern_id())
-    }
-
-    fn from_chalk(_db: &dyn HirDatabase, impl_id: ImplId) -> hir_def::ImplId {
-        InternKey::from_intern_id(impl_id.0)
-    }
-}
-
-impl ToChalk for CallableDefId {
-    type Chalk = FnDefId;
-
-    fn to_chalk(self, db: &dyn HirDatabase) -> FnDefId {
-        db.intern_callable_def(self).into()
-    }
-
-    fn from_chalk(db: &dyn HirDatabase, fn_def_id: FnDefId) -> CallableDefId {
-        db.lookup_intern_callable_def(fn_def_id.into())
-    }
-}
-
-pub(crate) struct TypeAliasAsValue(pub(crate) TypeAliasId);
-
-impl ToChalk for TypeAliasAsValue {
-    type Chalk = AssociatedTyValueId;
-
-    fn to_chalk(self, _db: &dyn HirDatabase) -> AssociatedTyValueId {
-        rust_ir::AssociatedTyValueId(self.0.as_intern_id())
-    }
-
-    fn from_chalk(
-        _db: &dyn HirDatabase,
-        assoc_ty_value_id: AssociatedTyValueId,
-    ) -> TypeAliasAsValue {
-        TypeAliasAsValue(TypeAliasId::from_intern_id(assoc_ty_value_id.0))
-    }
-}
-
-pub(super) fn convert_where_clauses(
-    db: &dyn HirDatabase,
-    def: GenericDefId,
-    substs: &Substitution,
-) -> Vec<chalk_ir::QuantifiedWhereClause<Interner>> {
-    let generic_predicates = db.generic_predicates(def);
-    let mut result = Vec::with_capacity(generic_predicates.len());
-    for pred in generic_predicates.iter() {
-        result.push(pred.clone().substitute(&Interner, substs));
-    }
-    result
-}
-
-pub(super) fn generic_predicate_to_inline_bound(
-    db: &dyn HirDatabase,
-    pred: &QuantifiedWhereClause,
-    self_ty: &Ty,
-) -> Option<chalk_ir::Binders<rust_ir::InlineBound<Interner>>> {
-    // An InlineBound is like a GenericPredicate, except the self type is left out.
-    // We don't have a special type for this, but Chalk does.
-    let self_ty_shifted_in = self_ty.clone().shifted_in_from(&Interner, DebruijnIndex::ONE);
-    let (pred, binders) = pred.as_ref().into_value_and_skipped_binders();
-    match pred {
-        WhereClause::Implemented(trait_ref) => {
-            if trait_ref.self_type_parameter(&Interner) != self_ty_shifted_in {
-                // we can only convert predicates back to type bounds if they
-                // have the expected self type
-                return None;
-            }
-            let args_no_self = trait_ref.substitution.as_slice(&Interner)[1..]
-                .iter()
-                .map(|ty| ty.clone().cast(&Interner))
-                .collect();
-            let trait_bound = rust_ir::TraitBound { trait_id: trait_ref.trait_id, args_no_self };
-            Some(chalk_ir::Binders::new(binders, rust_ir::InlineBound::TraitBound(trait_bound)))
-        }
-        WhereClause::AliasEq(AliasEq { alias: AliasTy::Projection(projection_ty), ty }) => {
-            if projection_ty.self_type_parameter(&Interner) != self_ty_shifted_in {
-                return None;
-            }
-            let trait_ = projection_ty.trait_(db);
-            let args_no_self = projection_ty.substitution.as_slice(&Interner)[1..]
-                .iter()
-                .map(|ty| ty.clone().cast(&Interner))
-                .collect();
-            let alias_eq_bound = rust_ir::AliasEqBound {
-                value: ty.clone(),
-                trait_bound: rust_ir::TraitBound { trait_id: trait_.to_chalk(db), args_no_self },
-                associated_ty_id: projection_ty.associated_ty_id,
-                parameters: Vec::new(), // FIXME we don't support generic associated types yet
-            };
-            Some(chalk_ir::Binders::new(
-                binders,
-                rust_ir::InlineBound::AliasEqBound(alias_eq_bound),
-            ))
-        }
-        _ => None,
-    }
-}