Use `dyn Trait` for working with databse

It improves compile time in `--release` mode quite a bit, it doesn't
really slow things down and, conceptually, it seems closer to what we
want the physical architecture to look like (we don't want to
monomorphise EVERYTHING in a single leaf crate).

18 files changed, 337 insertions, 346 deletions

diff --git a/crates/ra_hir_ty/src/autoderef.rs b/crates/ra_hir_ty/src/autoderef.rs
index f32d5786a..53e81e85d 100644
--- a/crates/ra_hir_ty/src/autoderef.rs
+++ b/crates/ra_hir_ty/src/autoderef.rs
@@ -20,7 +20,7 @@ use crate::{
 const AUTODEREF_RECURSION_LIMIT: usize = 10;
 
 pub fn autoderef<'a>(
-    db: &'a impl HirDatabase,
+    db: &'a dyn HirDatabase,
     krate: Option<CrateId>,
     ty: InEnvironment<Canonical<Ty>>,
 ) -> impl Iterator<Item = Canonical<Ty>> + 'a {
@@ -32,7 +32,7 @@ pub fn autoderef<'a>(
 }
 
 pub(crate) fn deref(
-    db: &impl HirDatabase,
+    db: &dyn HirDatabase,
     krate: CrateId,
     ty: InEnvironment<&Canonical<Ty>>,
 ) -> Option<Canonical<Ty>> {
@@ -44,7 +44,7 @@ pub(crate) fn deref(
 }
 
 fn deref_by_trait(
-    db: &impl HirDatabase,
+    db: &dyn HirDatabase,
     krate: CrateId,
     ty: InEnvironment<&Canonical<Ty>>,
 ) -> Option<Canonical<Ty>> {
@@ -54,7 +54,7 @@ fn deref_by_trait(
     };
     let target = db.trait_data(deref_trait).associated_type_by_name(&name![Target])?;
 
-    let generic_params = generics(db, target.into());
+    let generic_params = generics(db.upcast(), target.into());
     if generic_params.len() != 1 {
         // the Target type + Deref trait should only have one generic parameter,
         // namely Deref's Self type
diff --git a/crates/ra_hir_ty/src/db.rs b/crates/ra_hir_ty/src/db.rs
index 74b309005..11fc2ac3d 100644
--- a/crates/ra_hir_ty/src/db.rs
+++ b/crates/ra_hir_ty/src/db.rs
@@ -7,7 +7,7 @@ use hir_def::{
     VariantId,
 };
 use ra_arena::map::ArenaMap;
-use ra_db::{impl_intern_key, salsa, CrateId};
+use ra_db::{impl_intern_key, salsa, CrateId, Upcast};
 use ra_prof::profile;
 
 use crate::{
@@ -20,7 +20,7 @@ use hir_expand::name::Name;
 
 #[salsa::query_group(HirDatabaseStorage)]
 #[salsa::requires(salsa::Database)]
-pub trait HirDatabase: DefDatabase {
+pub trait HirDatabase: DefDatabase + Upcast<dyn DefDatabase> {
     #[salsa::invoke(infer_wait)]
     fn infer(&self, def: DefWithBodyId) -> Arc<InferenceResult>;
 
diff --git a/crates/ra_hir_ty/src/display.rs b/crates/ra_hir_ty/src/display.rs
index 14e089cf4..a6ef44a31 100644
--- a/crates/ra_hir_ty/src/display.rs
+++ b/crates/ra_hir_ty/src/display.rs
@@ -9,8 +9,8 @@ use crate::{
 use hir_def::{generics::TypeParamProvenance, AdtId, AssocContainerId, Lookup};
 use hir_expand::name::Name;
 
-pub struct HirFormatter<'a, 'b, DB> {
-    pub db: &'a DB,
+pub struct HirFormatter<'a, 'b> {
+    pub db: &'a dyn HirDatabase,
     fmt: &'a mut fmt::Formatter<'b>,
     buf: String,
     curr_size: usize,
@@ -19,20 +19,20 @@ pub struct HirFormatter<'a, 'b, DB> {
 }
 
 pub trait HirDisplay {
-    fn hir_fmt(&self, f: &mut HirFormatter<impl HirDatabase>) -> fmt::Result;
+    fn hir_fmt(&self, f: &mut HirFormatter) -> fmt::Result;
 
-    fn display<'a, DB>(&'a self, db: &'a DB) -> HirDisplayWrapper<'a, DB, Self>
+    fn display<'a>(&'a self, db: &'a dyn HirDatabase) -> HirDisplayWrapper<'a, Self>
     where
         Self: Sized,
     {
         HirDisplayWrapper(db, self, None, false)
     }
 
-    fn display_truncated<'a, DB>(
+    fn display_truncated<'a>(
         &'a self,
-        db: &'a DB,
+        db: &'a dyn HirDatabase,
         max_size: Option<usize>,
-    ) -> HirDisplayWrapper<'a, DB, Self>
+    ) -> HirDisplayWrapper<'a, Self>
     where
         Self: Sized,
     {
@@ -40,10 +40,7 @@ pub trait HirDisplay {
     }
 }
 
-impl<'a, 'b, DB> HirFormatter<'a, 'b, DB>
-where
-    DB: HirDatabase,
-{
+impl<'a, 'b> HirFormatter<'a, 'b> {
     pub fn write_joined<T: HirDisplay>(
         &mut self,
         iter: impl IntoIterator<Item = T>,
@@ -84,11 +81,10 @@ where
     }
 }
 
-pub struct HirDisplayWrapper<'a, DB, T>(&'a DB, &'a T, Option<usize>, bool);
+pub struct HirDisplayWrapper<'a, T>(&'a dyn HirDatabase, &'a T, Option<usize>, bool);
 
-impl<'a, DB, T> fmt::Display for HirDisplayWrapper<'a, DB, T>
+impl<'a, T> fmt::Display for HirDisplayWrapper<'a, T>
 where
-    DB: HirDatabase,
     T: HirDisplay,
 {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
@@ -106,13 +102,13 @@ where
 const TYPE_HINT_TRUNCATION: &str = "…";
 
 impl HirDisplay for &Ty {
-    fn hir_fmt(&self, f: &mut HirFormatter<impl HirDatabase>) -> fmt::Result {
+    fn hir_fmt(&self, f: &mut HirFormatter) -> fmt::Result {
         HirDisplay::hir_fmt(*self, f)
     }
 }
 
 impl HirDisplay for ApplicationTy {
-    fn hir_fmt(&self, f: &mut HirFormatter<impl HirDatabase>) -> fmt::Result {
+    fn hir_fmt(&self, f: &mut HirFormatter) -> fmt::Result {
         if f.should_truncate() {
             return write!(f, "{}", TYPE_HINT_TRUNCATION);
         }
@@ -178,7 +174,7 @@ impl HirDisplay for ApplicationTy {
                     }
                 }
                 if self.parameters.len() > 0 {
-                    let generics = generics(f.db, def.into());
+                    let generics = generics(f.db.upcast(), def.into());
                     let (parent_params, self_param, type_params, _impl_trait_params) =
                         generics.provenance_split();
                     let total_len = parent_params + self_param + type_params;
@@ -238,7 +234,7 @@ impl HirDisplay for ApplicationTy {
                 }
             }
             TypeCtor::AssociatedType(type_alias) => {
-                let trait_ = match type_alias.lookup(f.db).container {
+                let trait_ = match type_alias.lookup(f.db.upcast()).container {
                     AssocContainerId::TraitId(it) => it,
                     _ => panic!("not an associated type"),
                 };
@@ -272,7 +268,7 @@ impl HirDisplay for ApplicationTy {
 }
 
 impl HirDisplay for ProjectionTy {
-    fn hir_fmt(&self, f: &mut HirFormatter<impl HirDatabase>) -> fmt::Result {
+    fn hir_fmt(&self, f: &mut HirFormatter) -> fmt::Result {
         if f.should_truncate() {
             return write!(f, "{}", TYPE_HINT_TRUNCATION);
         }
@@ -290,7 +286,7 @@ impl HirDisplay for ProjectionTy {
 }
 
 impl HirDisplay for Ty {
-    fn hir_fmt(&self, f: &mut HirFormatter<impl HirDatabase>) -> fmt::Result {
+    fn hir_fmt(&self, f: &mut HirFormatter) -> fmt::Result {
         if f.should_truncate() {
             return write!(f, "{}", TYPE_HINT_TRUNCATION);
         }
@@ -299,7 +295,7 @@ impl HirDisplay for Ty {
             Ty::Apply(a_ty) => a_ty.hir_fmt(f)?,
             Ty::Projection(p_ty) => p_ty.hir_fmt(f)?,
             Ty::Placeholder(id) => {
-                let generics = generics(f.db, id.parent);
+                let generics = generics(f.db.upcast(), id.parent);
                 let param_data = &generics.params.types[id.local_id];
                 match param_data.provenance {
                     TypeParamProvenance::TypeParamList | TypeParamProvenance::TraitSelf => {
@@ -334,7 +330,7 @@ impl HirDisplay for Ty {
 
 fn write_bounds_like_dyn_trait(
     predicates: &[GenericPredicate],
-    f: &mut HirFormatter<impl HirDatabase>,
+    f: &mut HirFormatter,
 ) -> fmt::Result {
     // Note: This code is written to produce nice results (i.e.
     // corresponding to surface Rust) for types that can occur in
@@ -398,7 +394,7 @@ fn write_bounds_like_dyn_trait(
 }
 
 impl TraitRef {
-    fn hir_fmt_ext(&self, f: &mut HirFormatter<impl HirDatabase>, use_as: bool) -> fmt::Result {
+    fn hir_fmt_ext(&self, f: &mut HirFormatter, use_as: bool) -> fmt::Result {
         if f.should_truncate() {
             return write!(f, "{}", TYPE_HINT_TRUNCATION);
         }
@@ -420,19 +416,19 @@ impl TraitRef {
 }
 
 impl HirDisplay for TraitRef {
-    fn hir_fmt(&self, f: &mut HirFormatter<impl HirDatabase>) -> fmt::Result {
+    fn hir_fmt(&self, f: &mut HirFormatter) -> fmt::Result {
         self.hir_fmt_ext(f, false)
     }
 }
 
 impl HirDisplay for &GenericPredicate {
-    fn hir_fmt(&self, f: &mut HirFormatter<impl HirDatabase>) -> fmt::Result {
+    fn hir_fmt(&self, f: &mut HirFormatter) -> fmt::Result {
         HirDisplay::hir_fmt(*self, f)
     }
 }
 
 impl HirDisplay for GenericPredicate {
-    fn hir_fmt(&self, f: &mut HirFormatter<impl HirDatabase>) -> fmt::Result {
+    fn hir_fmt(&self, f: &mut HirFormatter) -> fmt::Result {
         if f.should_truncate() {
             return write!(f, "{}", TYPE_HINT_TRUNCATION);
         }
@@ -456,7 +452,7 @@ impl HirDisplay for GenericPredicate {
 }
 
 impl HirDisplay for Obligation {
-    fn hir_fmt(&self, f: &mut HirFormatter<impl HirDatabase>) -> fmt::Result {
+    fn hir_fmt(&self, f: &mut HirFormatter) -> fmt::Result {
         match self {
             Obligation::Trait(tr) => write!(f, "Implements({})", tr.display(f.db)),
             Obligation::Projection(proj) => write!(
diff --git a/crates/ra_hir_ty/src/expr.rs b/crates/ra_hir_ty/src/expr.rs
index d8cdf5266..b7b476b4c 100644
--- a/crates/ra_hir_ty/src/expr.rs
+++ b/crates/ra_hir_ty/src/expr.rs
@@ -46,7 +46,7 @@ impl<'a, 'b> ExprValidator<'a, 'b> {
         ExprValidator { func, infer, sink }
     }
 
-    pub fn validate_body(&mut self, db: &impl HirDatabase) {
+    pub fn validate_body(&mut self, db: &dyn HirDatabase) {
         let body = db.body(self.func.into());
 
         for e in body.exprs.iter() {
@@ -67,7 +67,7 @@ impl<'a, 'b> ExprValidator<'a, 'b> {
         _path: &Option<Path>,
         fields: &[RecordLitField],
         spread: Option<ExprId>,
-        db: &impl HirDatabase,
+        db: &dyn HirDatabase,
     ) {
         if spread.is_some() {
             return;
@@ -80,7 +80,7 @@ impl<'a, 'b> ExprValidator<'a, 'b> {
             return;
         }
 
-        let variant_data = variant_data(db, variant_def);
+        let variant_data = variant_data(db.upcast(), variant_def);
 
         let lit_fields: FxHashSet<_> = fields.iter().map(|f| &f.name).collect();
         let missed_fields: Vec<Name> = variant_data
@@ -102,7 +102,7 @@ impl<'a, 'b> ExprValidator<'a, 'b> {
 
         if let Ok(source_ptr) = source_map.expr_syntax(id) {
             if let Some(expr) = source_ptr.value.left() {
-                let root = source_ptr.file_syntax(db);
+                let root = source_ptr.file_syntax(db.upcast());
                 if let ast::Expr::RecordLit(record_lit) = expr.to_node(&root) {
                     if let Some(field_list) = record_lit.record_field_list() {
                         self.sink.push(MissingFields {
@@ -116,12 +116,7 @@ impl<'a, 'b> ExprValidator<'a, 'b> {
         }
     }
 
-    fn validate_results_in_tail_expr(
-        &mut self,
-        body_id: ExprId,
-        id: ExprId,
-        db: &impl HirDatabase,
-    ) {
+    fn validate_results_in_tail_expr(&mut self, body_id: ExprId, id: ExprId, db: &dyn HirDatabase) {
         // the mismatch will be on the whole block currently
         let mismatch = match self.infer.type_mismatch_for_expr(body_id) {
             Some(m) => m,
@@ -130,8 +125,8 @@ impl<'a, 'b> ExprValidator<'a, 'b> {
 
         let std_result_path = path![std::result::Result];
 
-        let resolver = self.func.resolver(db);
-        let std_result_enum = match resolver.resolve_known_enum(db, &std_result_path) {
+        let resolver = self.func.resolver(db.upcast());
+        let std_result_enum = match resolver.resolve_known_enum(db.upcast(), &std_result_path) {
             Some(it) => it,
             _ => return,
         };
diff --git a/crates/ra_hir_ty/src/infer.rs b/crates/ra_hir_ty/src/infer.rs
index 947833412..246b0e9be 100644
--- a/crates/ra_hir_ty/src/infer.rs
+++ b/crates/ra_hir_ty/src/infer.rs
@@ -63,9 +63,9 @@ mod pat;
 mod coerce;
 
 /// The entry point of type inference.
-pub(crate) fn infer_query(db: &impl HirDatabase, def: DefWithBodyId) -> Arc<InferenceResult> {
+pub(crate) fn infer_query(db: &dyn HirDatabase, def: DefWithBodyId) -> Arc<InferenceResult> {
     let _p = profile("infer_query");
-    let resolver = def.resolver(db);
+    let resolver = def.resolver(db.upcast());
     let mut ctx = InferenceContext::new(db, def, resolver);
 
     match def {
@@ -164,7 +164,7 @@ impl InferenceResult {
     }
     pub fn add_diagnostics(
         &self,
-        db: &impl HirDatabase,
+        db: &dyn HirDatabase,
         owner: FunctionId,
         sink: &mut DiagnosticSink,
     ) {
@@ -190,8 +190,8 @@ impl Index<PatId> for InferenceResult {
 
 /// The inference context contains all information needed during type inference.
 #[derive(Clone, Debug)]
-struct InferenceContext<'a, D: HirDatabase> {
-    db: &'a D,
+struct InferenceContext<'a> {
+    db: &'a dyn HirDatabase,
     owner: DefWithBodyId,
     body: Arc<Body>,
     resolver: Resolver,
@@ -208,8 +208,8 @@ struct InferenceContext<'a, D: HirDatabase> {
     return_ty: Ty,
 }
 
-impl<'a, D: HirDatabase> InferenceContext<'a, D> {
-    fn new(db: &'a D, owner: DefWithBodyId, resolver: Resolver) -> Self {
+impl<'a> InferenceContext<'a> {
+    fn new(db: &'a dyn HirDatabase, owner: DefWithBodyId, resolver: Resolver) -> Self {
         InferenceContext {
             result: InferenceResult::default(),
             table: unify::InferenceTable::new(),
@@ -425,7 +425,7 @@ impl<'a, D: HirDatabase> InferenceContext<'a, D> {
         let ctx = crate::lower::TyLoweringContext::new(self.db, &self.resolver);
         // FIXME: this should resolve assoc items as well, see this example:
         // https://play.rust-lang.org/?gist=087992e9e22495446c01c0d4e2d69521
-        return match resolver.resolve_path_in_type_ns_fully(self.db, path.mod_path()) {
+        return match resolver.resolve_path_in_type_ns_fully(self.db.upcast(), path.mod_path()) {
             Some(TypeNs::AdtId(AdtId::StructId(strukt))) => {
                 let substs = Ty::substs_from_path(&ctx, path, strukt.into());
                 let ty = self.db.ty(strukt.into());
@@ -439,7 +439,7 @@ impl<'a, D: HirDatabase> InferenceContext<'a, D> {
                 (ty, Some(var.into()))
             }
             Some(TypeNs::SelfType(impl_id)) => {
-                let generics = crate::utils::generics(self.db, impl_id.into());
+                let generics = crate::utils::generics(self.db.upcast(), impl_id.into());
                 let substs = Substs::type_params_for_generics(&generics);
                 let ty = self.db.impl_self_ty(impl_id).subst(&substs);
                 let variant = ty_variant(&ty);
@@ -500,13 +500,13 @@ impl<'a, D: HirDatabase> InferenceContext<'a, D> {
 
     fn resolve_into_iter_item(&self) -> Option<TypeAliasId> {
         let path = path![std::iter::IntoIterator];
-        let trait_ = self.resolver.resolve_known_trait(self.db, &path)?;
+        let trait_ = self.resolver.resolve_known_trait(self.db.upcast(), &path)?;
         self.db.trait_data(trait_).associated_type_by_name(&name![Item])
     }
 
     fn resolve_ops_try_ok(&self) -> Option<TypeAliasId> {
         let path = path![std::ops::Try];
-        let trait_ = self.resolver.resolve_known_trait(self.db, &path)?;
+        let trait_ = self.resolver.resolve_known_trait(self.db.upcast(), &path)?;
         self.db.trait_data(trait_).associated_type_by_name(&name![Ok])
     }
 
@@ -532,37 +532,37 @@ impl<'a, D: HirDatabase> InferenceContext<'a, D> {
 
     fn resolve_range_full(&self) -> Option<AdtId> {
         let path = path![std::ops::RangeFull];
-        let struct_ = self.resolver.resolve_known_struct(self.db, &path)?;
+        let struct_ = self.resolver.resolve_known_struct(self.db.upcast(), &path)?;
         Some(struct_.into())
     }
 
     fn resolve_range(&self) -> Option<AdtId> {
         let path = path![std::ops::Range];
-        let struct_ = self.resolver.resolve_known_struct(self.db, &path)?;
+        let struct_ = self.resolver.resolve_known_struct(self.db.upcast(), &path)?;
         Some(struct_.into())
     }
 
     fn resolve_range_inclusive(&self) -> Option<AdtId> {
         let path = path![std::ops::RangeInclusive];
-        let struct_ = self.resolver.resolve_known_struct(self.db, &path)?;
+        let struct_ = self.resolver.resolve_known_struct(self.db.upcast(), &path)?;
         Some(struct_.into())
     }
 
     fn resolve_range_from(&self) -> Option<AdtId> {
         let path = path![std::ops::RangeFrom];
-        let struct_ = self.resolver.resolve_known_struct(self.db, &path)?;
+        let struct_ = self.resolver.resolve_known_struct(self.db.upcast(), &path)?;
         Some(struct_.into())
     }
 
     fn resolve_range_to(&self) -> Option<AdtId> {
         let path = path![std::ops::RangeTo];
-        let struct_ = self.resolver.resolve_known_struct(self.db, &path)?;
+        let struct_ = self.resolver.resolve_known_struct(self.db.upcast(), &path)?;
         Some(struct_.into())
     }
 
     fn resolve_range_to_inclusive(&self) -> Option<AdtId> {
         let path = path![std::ops::RangeToInclusive];
-        let struct_ = self.resolver.resolve_known_struct(self.db, &path)?;
+        let struct_ = self.resolver.resolve_known_struct(self.db.upcast(), &path)?;
         Some(struct_.into())
     }
 
@@ -676,13 +676,13 @@ mod diagnostics {
     impl InferenceDiagnostic {
         pub(super) fn add_to(
             &self,
-            db: &impl HirDatabase,
+            db: &dyn HirDatabase,
             owner: FunctionId,
             sink: &mut DiagnosticSink,
         ) {
             match self {
                 InferenceDiagnostic::NoSuchField { expr, field } => {
-                    let file = owner.lookup(db).source(db).file_id;
+                    let file = owner.lookup(db.upcast()).source(db.upcast()).file_id;
                     let (_, source_map) = db.body_with_source_map(owner.into());
                     let field = source_map.field_syntax(*expr, *field);
                     sink.push(NoSuchField { file, field })
diff --git a/crates/ra_hir_ty/src/infer/coerce.rs b/crates/ra_hir_ty/src/infer/coerce.rs
index 95ac3c713..959b1e212 100644
--- a/crates/ra_hir_ty/src/infer/coerce.rs
+++ b/crates/ra_hir_ty/src/infer/coerce.rs
@@ -7,13 +7,11 @@
 use hir_def::{lang_item::LangItemTarget, type_ref::Mutability};
 use test_utils::tested_by;
 
-use crate::{
-    autoderef, db::HirDatabase, traits::Solution, Obligation, Substs, TraitRef, Ty, TypeCtor,
-};
+use crate::{autoderef, traits::Solution, Obligation, Substs, TraitRef, Ty, TypeCtor};
 
 use super::{unify::TypeVarValue, InEnvironment, InferTy, InferenceContext};
 
-impl<'a, D: HirDatabase> InferenceContext<'a, D> {
+impl<'a> InferenceContext<'a> {
     /// Unify two types, but may coerce the first one to the second one
     /// using "implicit coercion rules" if needed.
     pub(super) fn coerce(&mut self, from_ty: &Ty, to_ty: &Ty) -> bool {
@@ -126,7 +124,7 @@ impl<'a, D: HirDatabase> InferenceContext<'a, D> {
             _ => return None,
         };
 
-        let generic_params = crate::utils::generics(self.db, coerce_unsized_trait.into());
+        let generic_params = crate::utils::generics(self.db.upcast(), coerce_unsized_trait.into());
         if generic_params.len() != 2 {
             // The CoerceUnsized trait should have two generic params: Self and T.
             return None;
diff --git a/crates/ra_hir_ty/src/infer/expr.rs b/crates/ra_hir_ty/src/infer/expr.rs
index e89cc7298..1fdb235a0 100644
--- a/crates/ra_hir_ty/src/infer/expr.rs
+++ b/crates/ra_hir_ty/src/infer/expr.rs
@@ -14,9 +14,7 @@ use hir_expand::name::Name;
 use ra_syntax::ast::RangeOp;
 
 use crate::{
-    autoderef,
-    db::HirDatabase,
-    method_resolution, op,
+    autoderef, method_resolution, op,
     traits::InEnvironment,
     utils::{generics, variant_data, Generics},
     ApplicationTy, Binders, CallableDef, InferTy, IntTy, Mutability, Obligation, Substs, TraitRef,
@@ -25,7 +23,7 @@ use crate::{
 
 use super::{BindingMode, Expectation, InferenceContext, InferenceDiagnostic, TypeMismatch};
 
-impl<'a, D: HirDatabase> InferenceContext<'a, D> {
+impl<'a> InferenceContext<'a> {
     pub(super) fn infer_expr(&mut self, tgt_expr: ExprId, expected: &Expectation) -> Ty {
         let ty = self.infer_expr_inner(tgt_expr, expected);
         let could_unify = self.unify(&ty, &expected.ty);
@@ -184,7 +182,7 @@ impl<'a, D: HirDatabase> InferenceContext<'a, D> {
             }
             Expr::Path(p) => {
                 // FIXME this could be more efficient...
-                let resolver = resolver_for_expr(self.db, self.owner, tgt_expr);
+                let resolver = resolver_for_expr(self.db.upcast(), self.owner, tgt_expr);
                 self.infer_path(&resolver, p, tgt_expr.into()).unwrap_or(Ty::Unknown)
             }
             Expr::Continue => Ty::simple(TypeCtor::Never),
@@ -214,7 +212,7 @@ impl<'a, D: HirDatabase> InferenceContext<'a, D> {
 
                 let substs = ty.substs().unwrap_or_else(Substs::empty);
                 let field_types = def_id.map(|it| self.db.field_types(it)).unwrap_or_default();
-                let variant_data = def_id.map(|it| variant_data(self.db, it));
+                let variant_data = def_id.map(|it| variant_data(self.db.upcast(), it));
                 for (field_idx, field) in fields.iter().enumerate() {
                     let field_def =
                         variant_data.as_ref().and_then(|it| match it.field(&field.name) {
@@ -579,7 +577,7 @@ impl<'a, D: HirDatabase> InferenceContext<'a, D> {
         let receiver_ty = self.infer_expr(receiver, &Expectation::none());
         let canonicalized_receiver = self.canonicalizer().canonicalize_ty(receiver_ty.clone());
 
-        let traits_in_scope = self.resolver.traits_in_scope(self.db);
+        let traits_in_scope = self.resolver.traits_in_scope(self.db.upcast());
 
         let resolved = self.resolver.krate().and_then(|krate| {
             method_resolution::lookup_method(
@@ -595,7 +593,7 @@ impl<'a, D: HirDatabase> InferenceContext<'a, D> {
             Some((ty, func)) => {
                 let ty = canonicalized_receiver.decanonicalize_ty(ty);
                 self.write_method_resolution(tgt_expr, func);
-                (ty, self.db.value_ty(func.into()), Some(generics(self.db, func.into())))
+                (ty, self.db.value_ty(func.into()), Some(generics(self.db.upcast(), func.into())))
             }
             None => (receiver_ty, Binders::new(0, Ty::Unknown), None),
         };
@@ -703,10 +701,13 @@ impl<'a, D: HirDatabase> InferenceContext<'a, D> {
                 // add obligation for trait implementation, if this is a trait method
                 match def {
                     CallableDef::FunctionId(f) => {
-                        if let AssocContainerId::TraitId(trait_) = f.lookup(self.db).container {
+                        if let AssocContainerId::TraitId(trait_) =
+                            f.lookup(self.db.upcast()).container
+                        {
                             // construct a TraitDef
-                            let substs =
-                                a_ty.parameters.prefix(generics(self.db, trait_.into()).len());
+                            let substs = a_ty
+                                .parameters
+                                .prefix(generics(self.db.upcast(), trait_.into()).len());
                             self.obligations.push(Obligation::Trait(TraitRef { trait_, substs }));
                         }
                     }
diff --git a/crates/ra_hir_ty/src/infer/pat.rs b/crates/ra_hir_ty/src/infer/pat.rs
index 7a84e47f8..baed6225b 100644
--- a/crates/ra_hir_ty/src/infer/pat.rs
+++ b/crates/ra_hir_ty/src/infer/pat.rs
@@ -12,9 +12,9 @@ use hir_expand::name::Name;
 use test_utils::tested_by;
 
 use super::{BindingMode, InferenceContext};
-use crate::{db::HirDatabase, utils::variant_data, Substs, Ty, TypeCtor};
+use crate::{utils::variant_data, Substs, Ty, TypeCtor};
 
-impl<'a, D: HirDatabase> InferenceContext<'a, D> {
+impl<'a> InferenceContext<'a> {
     fn infer_tuple_struct_pat(
         &mut self,
         path: Option<&Path>,
@@ -23,7 +23,7 @@ impl<'a, D: HirDatabase> InferenceContext<'a, D> {
         default_bm: BindingMode,
     ) -> Ty {
         let (ty, def) = self.resolve_variant(path);
-        let var_data = def.map(|it| variant_data(self.db, it));
+        let var_data = def.map(|it| variant_data(self.db.upcast(), it));
         self.unify(&ty, expected);
 
         let substs = ty.substs().unwrap_or_else(Substs::empty);
@@ -51,7 +51,7 @@ impl<'a, D: HirDatabase> InferenceContext<'a, D> {
         id: PatId,
     ) -> Ty {
         let (ty, def) = self.resolve_variant(path);
-        let var_data = def.map(|it| variant_data(self.db, it));
+        let var_data = def.map(|it| variant_data(self.db.upcast(), it));
         if let Some(variant) = def {
             self.write_variant_resolution(id.into(), variant);
         }
diff --git a/crates/ra_hir_ty/src/infer/path.rs b/crates/ra_hir_ty/src/infer/path.rs
index c733b9e1d..318652c61 100644
--- a/crates/ra_hir_ty/src/infer/path.rs
+++ b/crates/ra_hir_ty/src/infer/path.rs
@@ -9,11 +9,11 @@ use hir_def::{
 };
 use hir_expand::name::Name;
 
-use crate::{db::HirDatabase, method_resolution, Substs, Ty, ValueTyDefId};
+use crate::{method_resolution, Substs, Ty, ValueTyDefId};
 
 use super::{ExprOrPatId, InferenceContext, TraitRef};
 
-impl<'a, D: HirDatabase> InferenceContext<'a, D> {
+impl<'a> InferenceContext<'a> {
     pub(super) fn infer_path(
         &mut self,
         resolver: &Resolver,
@@ -47,7 +47,8 @@ impl<'a, D: HirDatabase> InferenceContext<'a, D> {
                 id,
             )?
         } else {
-            let value_or_partial = resolver.resolve_path_in_value_ns(self.db, path.mod_path())?;
+            let value_or_partial =
+                resolver.resolve_path_in_value_ns(self.db.upcast(), path.mod_path())?;
 
             match value_or_partial {
                 ResolveValueResult::ValueNs(it) => (it, None),
@@ -192,7 +193,7 @@ impl<'a, D: HirDatabase> InferenceContext<'a, D> {
 
         let canonical_ty = self.canonicalizer().canonicalize_ty(ty.clone());
         let krate = self.resolver.krate()?;
-        let traits_in_scope = self.resolver.traits_in_scope(self.db);
+        let traits_in_scope = self.resolver.traits_in_scope(self.db.upcast());
 
         method_resolution::iterate_method_candidates(
             &canonical_ty.value,
@@ -205,9 +206,11 @@ impl<'a, D: HirDatabase> InferenceContext<'a, D> {
             move |_ty, item| {
                 let (def, container) = match item {
                     AssocItemId::FunctionId(f) => {
-                        (ValueNs::FunctionId(f), f.lookup(self.db).container)
+                        (ValueNs::FunctionId(f), f.lookup(self.db.upcast()).container)
+                    }
+                    AssocItemId::ConstId(c) => {
+                        (ValueNs::ConstId(c), c.lookup(self.db.upcast()).container)
                     }
-                    AssocItemId::ConstId(c) => (ValueNs::ConstId(c), c.lookup(self.db).container),
                     AssocItemId::TypeAliasId(_) => unreachable!(),
                 };
                 let substs = match container {
diff --git a/crates/ra_hir_ty/src/infer/unify.rs b/crates/ra_hir_ty/src/infer/unify.rs
index 82b85d570..0bf8fbd63 100644
--- a/crates/ra_hir_ty/src/infer/unify.rs
+++ b/crates/ra_hir_ty/src/infer/unify.rs
@@ -7,10 +7,10 @@ use ena::unify::{InPlaceUnificationTable, NoError, UnifyKey, UnifyValue};
 use test_utils::tested_by;
 
 use super::{InferenceContext, Obligation};
-use crate::{db::HirDatabase, Canonical, InEnvironment, InferTy, Substs, Ty, TypeCtor, TypeWalk};
+use crate::{Canonical, InEnvironment, InferTy, Substs, Ty, TypeCtor, TypeWalk};
 
-impl<'a, D: HirDatabase> InferenceContext<'a, D> {
-    pub(super) fn canonicalizer<'b>(&'b mut self) -> Canonicalizer<'a, 'b, D>
+impl<'a> InferenceContext<'a> {
+    pub(super) fn canonicalizer<'b>(&'b mut self) -> Canonicalizer<'a, 'b>
     where
         'a: 'b,
     {
@@ -18,11 +18,11 @@ impl<'a, D: HirDatabase> InferenceContext<'a, D> {
     }
 }
 
-pub(super) struct Canonicalizer<'a, 'b, D: HirDatabase>
+pub(super) struct Canonicalizer<'a, 'b>
 where
     'a: 'b,
 {
-    ctx: &'b mut InferenceContext<'a, D>,
+    ctx: &'b mut InferenceContext<'a>,
     free_vars: Vec<InferTy>,
     /// A stack of type variables that is used to detect recursive types (which
     /// are an error, but we need to protect against them to avoid stack
@@ -35,7 +35,7 @@ pub(super) struct Canonicalized<T> {
     free_vars: Vec<InferTy>,
 }
 
-impl<'a, 'b, D: HirDatabase> Canonicalizer<'a, 'b, D>
+impl<'a, 'b> Canonicalizer<'a, 'b>
 where
     'a: 'b,
 {
@@ -123,11 +123,7 @@ impl<T> Canonicalized<T> {
         ty
     }
 
-    pub fn apply_solution(
-        &self,
-        ctx: &mut InferenceContext<'_, impl HirDatabase>,
-        solution: Canonical<Vec<Ty>>,
-    ) {
+    pub fn apply_solution(&self, ctx: &mut InferenceContext<'_>, solution: Canonical<Vec<Ty>>) {
         // the solution may contain new variables, which we need to convert to new inference vars
         let new_vars = Substs((0..solution.num_vars).map(|_| ctx.table.new_type_var()).collect());
         for (i, ty) in solution.value.into_iter().enumerate() {
diff --git a/crates/ra_hir_ty/src/lib.rs b/crates/ra_hir_ty/src/lib.rs
index 4127f1a8d..6c5469ecd 100644
--- a/crates/ra_hir_ty/src/lib.rs
+++ b/crates/ra_hir_ty/src/lib.rs
@@ -152,7 +152,7 @@ pub struct TypeCtorId(salsa::InternId);
 impl_intern_key!(TypeCtorId);
 
 impl TypeCtor {
-    pub fn num_ty_params(self, db: &impl HirDatabase) -> usize {
+    pub fn num_ty_params(self, db: &dyn HirDatabase) -> usize {
         match self {
             TypeCtor::Bool
             | TypeCtor::Char
@@ -167,15 +167,15 @@ impl TypeCtor {
             | TypeCtor::Closure { .. } // 1 param representing the signature of the closure
             => 1,
             TypeCtor::Adt(adt) => {
-                let generic_params = generics(db, adt.into());
+                let generic_params = generics(db.upcast(), adt.into());
                 generic_params.len()
             }
             TypeCtor::FnDef(callable) => {
-                let generic_params = generics(db, callable.into());
+                let generic_params = generics(db.upcast(), callable.into());
                 generic_params.len()
             }
             TypeCtor::AssociatedType(type_alias) => {
-                let generic_params = generics(db, type_alias.into());
+                let generic_params = generics(db.upcast(), type_alias.into());
                 generic_params.len()
             }
             TypeCtor::FnPtr { num_args } => num_args as usize + 1,
@@ -183,7 +183,7 @@ impl TypeCtor {
         }
     }
 
-    pub fn krate(self, db: &impl HirDatabase) -> Option<CrateId> {
+    pub fn krate(self, db: &dyn HirDatabase) -> Option<CrateId> {
         match self {
             TypeCtor::Bool
             | TypeCtor::Char
@@ -199,9 +199,11 @@ impl TypeCtor {
             | TypeCtor::Tuple { .. } => None,
             // Closure's krate is irrelevant for coherence I would think?
             TypeCtor::Closure { .. } => None,
-            TypeCtor::Adt(adt) => Some(adt.module(db).krate),
+            TypeCtor::Adt(adt) => Some(adt.module(db.upcast()).krate),
             TypeCtor::FnDef(callable) => Some(callable.krate(db)),
-            TypeCtor::AssociatedType(type_alias) => Some(type_alias.lookup(db).module(db).krate),
+            TypeCtor::AssociatedType(type_alias) => {
+                Some(type_alias.lookup(db.upcast()).module(db.upcast()).krate)
+            }
         }
     }
 
@@ -246,12 +248,12 @@ pub struct ProjectionTy {
 }
 
 impl ProjectionTy {
-    pub fn trait_ref(&self, db: &impl HirDatabase) -> TraitRef {
+    pub fn trait_ref(&self, db: &dyn HirDatabase) -> TraitRef {
         TraitRef { trait_: self.trait_(db), substs: self.parameters.clone() }
     }
 
-    fn trait_(&self, db: &impl HirDatabase) -> TraitId {
-        match self.associated_ty.lookup(db).container {
+    fn trait_(&self, db: &dyn HirDatabase) -> TraitId {
+        match self.associated_ty.lookup(db.upcast()).container {
             AssocContainerId::TraitId(it) => it,
             _ => panic!("projection ty without parent trait"),
         }
@@ -372,8 +374,8 @@ impl Substs {
     }
 
     /// Return Substs that replace each parameter by itself (i.e. `Ty::Param`).
-    pub fn type_params(db: &impl HirDatabase, def: impl Into<GenericDefId>) -> Substs {
-        let params = generics(db, def.into());
+    pub fn type_params(db: &dyn HirDatabase, def: impl Into<GenericDefId>) -> Substs {
+        let params = generics(db.upcast(), def.into());
         Substs::type_params_for_generics(&params)
     }
 
@@ -382,9 +384,9 @@ impl Substs {
         Substs(generic_params.iter().enumerate().map(|(idx, _)| Ty::Bound(idx as u32)).collect())
     }
 
-    pub fn build_for_def(db: &impl HirDatabase, def: impl Into<GenericDefId>) -> SubstsBuilder {
+    pub fn build_for_def(db: &dyn HirDatabase, def: impl Into<GenericDefId>) -> SubstsBuilder {
         let def = def.into();
-        let params = generics(db, def);
+        let params = generics(db.upcast(), def);
         let param_count = params.len();
         Substs::builder(param_count)
     }
@@ -393,7 +395,7 @@ impl Substs {
         Substs::builder(generic_params.len())
     }
 
-    pub fn build_for_type_ctor(db: &impl HirDatabase, type_ctor: TypeCtor) -> SubstsBuilder {
+    pub fn build_for_type_ctor(db: &dyn HirDatabase, type_ctor: TypeCtor) -> SubstsBuilder {
         Substs::builder(type_ctor.num_ty_params(db))
     }
 
@@ -538,7 +540,7 @@ impl GenericPredicate {
         }
     }
 
-    pub fn trait_ref(&self, db: &impl HirDatabase) -> Option<TraitRef> {
+    pub fn trait_ref(&self, db: &dyn HirDatabase) -> Option<TraitRef> {
         match self {
             GenericPredicate::Implemented(tr) => Some(tr.clone()),
             GenericPredicate::Projection(proj) => Some(proj.projection_ty.trait_ref(db)),
@@ -693,7 +695,7 @@ impl Ty {
         }
     }
 
-    fn callable_sig(&self, db: &impl HirDatabase) -> Option<FnSig> {
+    fn callable_sig(&self, db: &dyn HirDatabase) -> Option<FnSig> {
         match self {
             Ty::Apply(a_ty) => match a_ty.ctor {
                 TypeCtor::FnPtr { .. } => Some(FnSig::from_fn_ptr_substs(&a_ty.parameters)),
diff --git a/crates/ra_hir_ty/src/lower.rs b/crates/ra_hir_ty/src/lower.rs
index b96dc126c..d7f250783 100644
--- a/crates/ra_hir_ty/src/lower.rs
+++ b/crates/ra_hir_ty/src/lower.rs
@@ -34,8 +34,8 @@ use crate::{
 };
 
 #[derive(Debug)]
-pub struct TyLoweringContext<'a, DB: HirDatabase> {
-    pub db: &'a DB,
+pub struct TyLoweringContext<'a> {
+    pub db: &'a dyn HirDatabase,
     pub resolver: &'a Resolver,
     /// Note: Conceptually, it's thinkable that we could be in a location where
     /// some type params should be represented as placeholders, and others
@@ -46,8 +46,8 @@ pub struct TyLoweringContext<'a, DB: HirDatabase> {
     pub impl_trait_counter: std::cell::Cell<u16>,
 }
 
-impl<'a, DB: HirDatabase> TyLoweringContext<'a, DB> {
-    pub fn new(db: &'a DB, resolver: &'a Resolver) -> Self {
+impl<'a> TyLoweringContext<'a> {
+    pub fn new(db: &'a dyn HirDatabase, resolver: &'a Resolver) -> Self {
         let impl_trait_counter = std::cell::Cell::new(0);
         let impl_trait_mode = ImplTraitLoweringMode::Disallowed;
         let type_param_mode = TypeParamLoweringMode::Placeholder;
@@ -90,13 +90,10 @@ pub enum TypeParamLoweringMode {
 }
 
 impl Ty {
-    pub fn from_hir(ctx: &TyLoweringContext<'_, impl HirDatabase>, type_ref: &TypeRef) -> Self {
+    pub fn from_hir(ctx: &TyLoweringContext<'_>, type_ref: &TypeRef) -> Self {
         Ty::from_hir_ext(ctx, type_ref).0
     }
-    pub fn from_hir_ext(
-        ctx: &TyLoweringContext<'_, impl HirDatabase>,
-        type_ref: &TypeRef,
-    ) -> (Self, Option<TypeNs>) {
+    pub fn from_hir_ext(ctx: &TyLoweringContext<'_>, type_ref: &TypeRef) -> (Self, Option<TypeNs>) {
         let mut res = None;
         let ty = match type_ref {
             TypeRef::Never => Ty::simple(TypeCtor::Never),
@@ -157,7 +154,7 @@ impl Ty {
                         let idx = ctx.impl_trait_counter.get();
                         ctx.impl_trait_counter.set(idx + 1);
                         if let Some(def) = ctx.resolver.generic_def() {
-                            let generics = generics(ctx.db, def);
+                            let generics = generics(ctx.db.upcast(), def);
                             let param = generics
                                 .iter()
                                 .filter(|(_, data)| {
@@ -175,7 +172,7 @@ impl Ty {
                         ctx.impl_trait_counter.set(idx + 1);
                         let (parent_params, self_params, list_params, _impl_trait_params) =
                             if let Some(def) = ctx.resolver.generic_def() {
-                                let generics = generics(ctx.db, def);
+                                let generics = generics(ctx.db.upcast(), def);
                                 generics.provenance_split()
                             } else {
                                 (0, 0, 0, 0)
@@ -201,10 +198,7 @@ impl Ty {
     /// This is only for `generic_predicates_for_param`, where we can't just
     /// lower the self types of the predicates since that could lead to cycles.
     /// So we just check here if the `type_ref` resolves to a generic param, and which.
-    fn from_hir_only_param(
-        ctx: &TyLoweringContext<'_, impl HirDatabase>,
-        type_ref: &TypeRef,
-    ) -> Option<TypeParamId> {
+    fn from_hir_only_param(ctx: &TyLoweringContext<'_>, type_ref: &TypeRef) -> Option<TypeParamId> {
         let path = match type_ref {
             TypeRef::Path(path) => path,
             _ => return None,
@@ -215,10 +209,11 @@ impl Ty {
         if path.segments().len() > 1 {
             return None;
         }
-        let resolution = match ctx.resolver.resolve_path_in_type_ns(ctx.db, path.mod_path()) {
-            Some((it, None)) => it,
-            _ => return None,
-        };
+        let resolution =
+            match ctx.resolver.resolve_path_in_type_ns(ctx.db.upcast(), path.mod_path()) {
+                Some((it, None)) => it,
+                _ => return None,
+            };
         if let TypeNs::GenericParam(param_id) = resolution {
             Some(param_id)
         } else {
@@ -227,7 +222,7 @@ impl Ty {
     }
 
     pub(crate) fn from_type_relative_path(
-        ctx: &TyLoweringContext<'_, impl HirDatabase>,
+        ctx: &TyLoweringContext<'_>,
         ty: Ty,
         // We need the original resolution to lower `Self::AssocTy` correctly
         res: Option<TypeNs>,
@@ -246,7 +241,7 @@ impl Ty {
     }
 
     pub(crate) fn from_partly_resolved_hir_path(
-        ctx: &TyLoweringContext<'_, impl HirDatabase>,
+        ctx: &TyLoweringContext<'_>,
         resolution: TypeNs,
         resolved_segment: PathSegment<'_>,
         remaining_segments: PathSegments<'_>,
@@ -260,7 +255,7 @@ impl Ty {
                 let ty = if remaining_segments.len() == 1 {
                     let segment = remaining_segments.first().unwrap();
                     let associated_ty = associated_type_by_name_including_super_traits(
-                        ctx.db,
+                        ctx.db.upcast(),
                         trait_ref.trait_,
                         &segment.name,
                     );
@@ -286,8 +281,10 @@ impl Ty {
                 return (ty, None);
             }
             TypeNs::GenericParam(param_id) => {
-                let generics =
-                    generics(ctx.db, ctx.resolver.generic_def().expect("generics in scope"));
+                let generics = generics(
+                    ctx.db.upcast(),
+                    ctx.resolver.generic_def().expect("generics in scope"),
+                );
                 match ctx.type_param_mode {
                     TypeParamLoweringMode::Placeholder => Ty::Placeholder(param_id),
                     TypeParamLoweringMode::Variable => {
@@ -297,7 +294,7 @@ impl Ty {
                 }
             }
             TypeNs::SelfType(impl_id) => {
-                let generics = generics(ctx.db, impl_id.into());
+                let generics = generics(ctx.db.upcast(), impl_id.into());
                 let substs = match ctx.type_param_mode {
                     TypeParamLoweringMode::Placeholder => {
                         Substs::type_params_for_generics(&generics)
@@ -307,7 +304,7 @@ impl Ty {
                 ctx.db.impl_self_ty(impl_id).subst(&substs)
             }
             TypeNs::AdtSelfType(adt) => {
-                let generics = generics(ctx.db, adt.into());
+                let generics = generics(ctx.db.upcast(), adt.into());
                 let substs = match ctx.type_param_mode {
                     TypeParamLoweringMode::Placeholder => {
                         Substs::type_params_for_generics(&generics)
@@ -327,17 +324,14 @@ impl Ty {
         Ty::from_type_relative_path(ctx, ty, Some(resolution), remaining_segments)
     }
 
-    pub(crate) fn from_hir_path(
-        ctx: &TyLoweringContext<'_, impl HirDatabase>,
-        path: &Path,
-    ) -> (Ty, Option<TypeNs>) {
+    pub(crate) fn from_hir_path(ctx: &TyLoweringContext<'_>, path: &Path) -> (Ty, Option<TypeNs>) {
         // Resolve the path (in type namespace)
         if let Some(type_ref) = path.type_anchor() {
             let (ty, res) = Ty::from_hir_ext(ctx, &type_ref);
             return Ty::from_type_relative_path(ctx, ty, res, path.segments());
         }
         let (resolution, remaining_index) =
-            match ctx.resolver.resolve_path_in_type_ns(ctx.db, path.mod_path()) {
+            match ctx.resolver.resolve_path_in_type_ns(ctx.db.upcast(), path.mod_path()) {
                 Some(it) => it,
                 None => return (Ty::Unknown, None),
             };
@@ -352,7 +346,7 @@ impl Ty {
     }
 
     fn select_associated_type(
-        ctx: &TyLoweringContext<'_, impl HirDatabase>,
+        ctx: &TyLoweringContext<'_>,
         self_ty: Ty,
         res: Option<TypeNs>,
         segment: PathSegment<'_>,
@@ -374,7 +368,7 @@ impl Ty {
             }
             _ => return Ty::Unknown,
         };
-        let traits = traits_from_env.into_iter().flat_map(|t| all_super_traits(ctx.db, t));
+        let traits = traits_from_env.into_iter().flat_map(|t| all_super_traits(ctx.db.upcast(), t));
         for t in traits {
             if let Some(associated_ty) = ctx.db.trait_data(t).associated_type_by_name(&segment.name)
             {
@@ -388,7 +382,7 @@ impl Ty {
     }
 
     fn from_hir_path_inner(
-        ctx: &TyLoweringContext<'_, impl HirDatabase>,
+        ctx: &TyLoweringContext<'_>,
         segment: PathSegment<'_>,
         typable: TyDefId,
     ) -> Ty {
@@ -404,7 +398,7 @@ impl Ty {
     /// Collect generic arguments from a path into a `Substs`. See also
     /// `create_substs_for_ast_path` and `def_to_ty` in rustc.
     pub(super) fn substs_from_path(
-        ctx: &TyLoweringContext<'_, impl HirDatabase>,
+        ctx: &TyLoweringContext<'_>,
         path: &Path,
         // Note that we don't call `db.value_type(resolved)` here,
         // `ValueTyDefId` is just a convenient way to pass generics and
@@ -437,13 +431,13 @@ impl Ty {
 }
 
 pub(super) fn substs_from_path_segment(
-    ctx: &TyLoweringContext<'_, impl HirDatabase>,
+    ctx: &TyLoweringContext<'_>,
     segment: PathSegment<'_>,
     def_generic: Option<GenericDefId>,
     _add_self_param: bool,
 ) -> Substs {
     let mut substs = Vec::new();
-    let def_generics = def_generic.map(|def| generics(ctx.db, def));
+    let def_generics = def_generic.map(|def| generics(ctx.db.upcast(), def));
 
     let (parent_params, self_params, type_params, impl_trait_params) =
         def_generics.map_or((0, 0, 0, 0), |g| g.provenance_split());
@@ -489,20 +483,21 @@ pub(super) fn substs_from_path_segment(
 
 impl TraitRef {
     fn from_path(
-        ctx: &TyLoweringContext<'_, impl HirDatabase>,
+        ctx: &TyLoweringContext<'_>,
         path: &Path,
         explicit_self_ty: Option<Ty>,
     ) -> Option<Self> {
-        let resolved = match ctx.resolver.resolve_path_in_type_ns_fully(ctx.db, path.mod_path())? {
-            TypeNs::TraitId(tr) => tr,
-            _ => return None,
-        };
+        let resolved =
+            match ctx.resolver.resolve_path_in_type_ns_fully(ctx.db.upcast(), path.mod_path())? {
+                TypeNs::TraitId(tr) => tr,
+                _ => return None,
+            };
         let segment = path.segments().last().expect("path should have at least one segment");
         Some(TraitRef::from_resolved_path(ctx, resolved, segment, explicit_self_ty))
     }
 
     pub(crate) fn from_resolved_path(
-        ctx: &TyLoweringContext<'_, impl HirDatabase>,
+        ctx: &TyLoweringContext<'_>,
         resolved: TraitId,
         segment: PathSegment<'_>,
         explicit_self_ty: Option<Ty>,
@@ -515,7 +510,7 @@ impl TraitRef {
     }
 
     fn from_hir(
-        ctx: &TyLoweringContext<'_, impl HirDatabase>,
+        ctx: &TyLoweringContext<'_>,
         type_ref: &TypeRef,
         explicit_self_ty: Option<Ty>,
     ) -> Option<Self> {
@@ -527,7 +522,7 @@ impl TraitRef {
     }
 
     fn substs_from_path(
-        ctx: &TyLoweringContext<'_, impl HirDatabase>,
+        ctx: &TyLoweringContext<'_>,
         segment: PathSegment<'_>,
         resolved: TraitId,
     ) -> Substs {
@@ -537,7 +532,7 @@ impl TraitRef {
     }
 
     pub(crate) fn from_type_bound(
-        ctx: &TyLoweringContext<'_, impl HirDatabase>,
+        ctx: &TyLoweringContext<'_>,
         bound: &TypeBound,
         self_ty: Ty,
     ) -> Option<TraitRef> {
@@ -550,14 +545,14 @@ impl TraitRef {
 
 impl GenericPredicate {
     pub(crate) fn from_where_predicate<'a>(
-        ctx: &'a TyLoweringContext<'a, impl HirDatabase>,
+        ctx: &'a TyLoweringContext<'a>,
         where_predicate: &'a WherePredicate,
     ) -> impl Iterator<Item = GenericPredicate> + 'a {
         let self_ty = match &where_predicate.target {
             WherePredicateTarget::TypeRef(type_ref) => Ty::from_hir(ctx, type_ref),
             WherePredicateTarget::TypeParam(param_id) => {
                 let generic_def = ctx.resolver.generic_def().expect("generics in scope");
-                let generics = generics(ctx.db, generic_def);
+                let generics = generics(ctx.db.upcast(), generic_def);
                 let param_id = hir_def::TypeParamId { parent: generic_def, local_id: *param_id };
                 match ctx.type_param_mode {
                     TypeParamLoweringMode::Placeholder => Ty::Placeholder(param_id),
@@ -572,7 +567,7 @@ impl GenericPredicate {
     }
 
     pub(crate) fn from_type_bound<'a>(
-        ctx: &'a TyLoweringContext<'a, impl HirDatabase>,
+        ctx: &'a TyLoweringContext<'a>,
         bound: &'a TypeBound,
         self_ty: Ty,
     ) -> impl Iterator<Item = GenericPredicate> + 'a {
@@ -587,7 +582,7 @@ impl GenericPredicate {
 }
 
 fn assoc_type_bindings_from_type_bound<'a>(
-    ctx: &'a TyLoweringContext<'a, impl HirDatabase>,
+    ctx: &'a TyLoweringContext<'a>,
     bound: &'a TypeBound,
     trait_ref: TraitRef,
 ) -> impl Iterator<Item = GenericPredicate> + 'a {
@@ -600,8 +595,11 @@ fn assoc_type_bindings_from_type_bound<'a>(
         .flat_map(|segment| segment.args_and_bindings.into_iter())
         .flat_map(|args_and_bindings| args_and_bindings.bindings.iter())
         .map(move |(name, type_ref)| {
-            let associated_ty =
-                associated_type_by_name_including_super_traits(ctx.db, trait_ref.trait_, &name);
+            let associated_ty = associated_type_by_name_including_super_traits(
+                ctx.db.upcast(),
+                trait_ref.trait_,
+                &name,
+            );
             let associated_ty = match associated_ty {
                 None => return GenericPredicate::Error,
                 Some(t) => t,
@@ -615,7 +613,7 @@ fn assoc_type_bindings_from_type_bound<'a>(
 }
 
 /// Build the signature of a callable item (function, struct or enum variant).
-pub fn callable_item_sig(db: &impl HirDatabase, def: CallableDef) -> PolyFnSig {
+pub fn callable_item_sig(db: &dyn HirDatabase, def: CallableDef) -> PolyFnSig {
     match def {
         CallableDef::FunctionId(f) => fn_sig_for_fn(db, f),
         CallableDef::StructId(s) => fn_sig_for_struct_constructor(db, s),
@@ -625,16 +623,16 @@ pub fn callable_item_sig(db: &impl HirDatabase, def: CallableDef) -> PolyFnSig {
 
 /// Build the type of all specific fields of a struct or enum variant.
 pub(crate) fn field_types_query(
-    db: &impl HirDatabase,
+    db: &dyn HirDatabase,
     variant_id: VariantId,
 ) -> Arc<ArenaMap<LocalStructFieldId, Binders<Ty>>> {
-    let var_data = variant_data(db, variant_id);
+    let var_data = variant_data(db.upcast(), variant_id);
     let (resolver, def): (_, GenericDefId) = match variant_id {
-        VariantId::StructId(it) => (it.resolver(db), it.into()),
-        VariantId::UnionId(it) => (it.resolver(db), it.into()),
-        VariantId::EnumVariantId(it) => (it.parent.resolver(db), it.parent.into()),
+        VariantId::StructId(it) => (it.resolver(db.upcast()), it.into()),
+        VariantId::UnionId(it) => (it.resolver(db.upcast()), it.into()),
+        VariantId::EnumVariantId(it) => (it.parent.resolver(db.upcast()), it.parent.into()),
     };
-    let generics = generics(db, def);
+    let generics = generics(db.upcast(), def);
     let mut res = ArenaMap::default();
     let ctx =
         TyLoweringContext::new(db, &resolver).with_type_param_mode(TypeParamLoweringMode::Variable);
@@ -653,13 +651,13 @@ pub(crate) fn field_types_query(
 /// following bounds are disallowed: `T: Foo<U::Item>, U: Foo<T::Item>`, but
 /// these are fine: `T: Foo<U::Item>, U: Foo<()>`.
 pub(crate) fn generic_predicates_for_param_query(
-    db: &impl HirDatabase,
+    db: &dyn HirDatabase,
     param_id: TypeParamId,
 ) -> Arc<[Binders<GenericPredicate>]> {
-    let resolver = param_id.parent.resolver(db);
+    let resolver = param_id.parent.resolver(db.upcast());
     let ctx =
         TyLoweringContext::new(db, &resolver).with_type_param_mode(TypeParamLoweringMode::Variable);
-    let generics = generics(db, param_id.parent);
+    let generics = generics(db.upcast(), param_id.parent);
     resolver
         .where_predicates_in_scope()
         // we have to filter out all other predicates *first*, before attempting to lower them
@@ -677,7 +675,7 @@ pub(crate) fn generic_predicates_for_param_query(
 }
 
 pub(crate) fn generic_predicates_for_param_recover(
-    _db: &impl HirDatabase,
+    _db: &dyn HirDatabase,
     _cycle: &[String],
     _param_id: &TypeParamId,
 ) -> Arc<[Binders<GenericPredicate>]> {
@@ -685,7 +683,7 @@ pub(crate) fn generic_predicates_for_param_recover(
 }
 
 impl TraitEnvironment {
-    pub fn lower(db: &impl HirDatabase, resolver: &Resolver) -> Arc<TraitEnvironment> {
+    pub fn lower(db: &dyn HirDatabase, resolver: &Resolver) -> Arc<TraitEnvironment> {
         let ctx = TyLoweringContext::new(db, &resolver)
             .with_type_param_mode(TypeParamLoweringMode::Placeholder);
         let mut predicates = resolver
@@ -696,13 +694,13 @@ impl TraitEnvironment {
         if let Some(def) = resolver.generic_def() {
             let container: Option<AssocContainerId> = match def {
                 // FIXME: is there a function for this?
-                GenericDefId::FunctionId(f) => Some(f.lookup(db).container),
+                GenericDefId::FunctionId(f) => Some(f.lookup(db.upcast()).container),
                 GenericDefId::AdtId(_) => None,
                 GenericDefId::TraitId(_) => None,
-                GenericDefId::TypeAliasId(t) => Some(t.lookup(db).container),
+                GenericDefId::TypeAliasId(t) => Some(t.lookup(db.upcast()).container),
                 GenericDefId::ImplId(_) => None,
                 GenericDefId::EnumVariantId(_) => None,
-                GenericDefId::ConstId(c) => Some(c.lookup(db).container),
+                GenericDefId::ConstId(c) => Some(c.lookup(db.upcast()).container),
             };
             if let Some(AssocContainerId::TraitId(trait_id)) = container {
                 // add `Self: Trait<T1, T2, ...>` to the environment in trait
@@ -723,13 +721,13 @@ impl TraitEnvironment {
 
 /// Resolve the where clause(s) of an item with generics.
 pub(crate) fn generic_predicates_query(
-    db: &impl HirDatabase,
+    db: &dyn HirDatabase,
     def: GenericDefId,
 ) -> Arc<[Binders<GenericPredicate>]> {
-    let resolver = def.resolver(db);
+    let resolver = def.resolver(db.upcast());
     let ctx =
         TyLoweringContext::new(db, &resolver).with_type_param_mode(TypeParamLoweringMode::Variable);
-    let generics = generics(db, def);
+    let generics = generics(db.upcast(), def);
     resolver
         .where_predicates_in_scope()
         .flat_map(|pred| {
@@ -740,10 +738,10 @@ pub(crate) fn generic_predicates_query(
 }
 
 /// Resolve the default type params from generics
-pub(crate) fn generic_defaults_query(db: &impl HirDatabase, def: GenericDefId) -> Substs {
-    let resolver = def.resolver(db);
+pub(crate) fn generic_defaults_query(db: &dyn HirDatabase, def: GenericDefId) -> Substs {
+    let resolver = def.resolver(db.upcast());
     let ctx = TyLoweringContext::new(db, &resolver);
-    let generic_params = generics(db, def);
+    let generic_params = generics(db.upcast(), def);
 
     let defaults = generic_params
         .iter()
@@ -753,33 +751,33 @@ pub(crate) fn generic_defaults_query(db: &impl HirDatabase, def: GenericDefId) -
     Substs(defaults)
 }
 
-fn fn_sig_for_fn(db: &impl HirDatabase, def: FunctionId) -> PolyFnSig {
+fn fn_sig_for_fn(db: &dyn HirDatabase, def: FunctionId) -> PolyFnSig {
     let data = db.function_data(def);
-    let resolver = def.resolver(db);
+    let resolver = def.resolver(db.upcast());
     let ctx_params = TyLoweringContext::new(db, &resolver)
         .with_impl_trait_mode(ImplTraitLoweringMode::Variable)
         .with_type_param_mode(TypeParamLoweringMode::Variable);
     let params = data.params.iter().map(|tr| Ty::from_hir(&ctx_params, tr)).collect::<Vec<_>>();
     let ctx_ret = ctx_params.with_impl_trait_mode(ImplTraitLoweringMode::Opaque);
     let ret = Ty::from_hir(&ctx_ret, &data.ret_type);
-    let generics = generics(db, def.into());
+    let generics = generics(db.upcast(), def.into());
     let num_binders = generics.len();
     Binders::new(num_binders, FnSig::from_params_and_return(params, ret))
 }
 
 /// Build the declared type of a function. This should not need to look at the
 /// function body.
-fn type_for_fn(db: &impl HirDatabase, def: FunctionId) -> Binders<Ty> {
-    let generics = generics(db, def.into());
+fn type_for_fn(db: &dyn HirDatabase, def: FunctionId) -> Binders<Ty> {
+    let generics = generics(db.upcast(), def.into());
     let substs = Substs::bound_vars(&generics);
     Binders::new(substs.len(), Ty::apply(TypeCtor::FnDef(def.into()), substs))
 }
 
 /// Build the declared type of a const.
-fn type_for_const(db: &impl HirDatabase, def: ConstId) -> Binders<Ty> {
+fn type_for_const(db: &dyn HirDatabase, def: ConstId) -> Binders<Ty> {
     let data = db.const_data(def);
-    let generics = generics(db, def.into());
-    let resolver = def.resolver(db);
+    let generics = generics(db.upcast(), def.into());
+    let resolver = def.resolver(db.upcast());
     let ctx =
         TyLoweringContext::new(db, &resolver).with_type_param_mode(TypeParamLoweringMode::Variable);
 
@@ -787,9 +785,9 @@ fn type_for_const(db: &impl HirDatabase, def: ConstId) -> Binders<Ty> {
 }
 
 /// Build the declared type of a static.
-fn type_for_static(db: &impl HirDatabase, def: StaticId) -> Binders<Ty> {
+fn type_for_static(db: &dyn HirDatabase, def: StaticId) -> Binders<Ty> {
     let data = db.static_data(def);
-    let resolver = def.resolver(db);
+    let resolver = def.resolver(db.upcast());
     let ctx = TyLoweringContext::new(db, &resolver);
 
     Binders::new(0, Ty::from_hir(&ctx, &data.type_ref))
@@ -806,10 +804,10 @@ fn type_for_builtin(def: BuiltinType) -> Ty {
     })
 }
 
-fn fn_sig_for_struct_constructor(db: &impl HirDatabase, def: StructId) -> PolyFnSig {
+fn fn_sig_for_struct_constructor(db: &dyn HirDatabase, def: StructId) -> PolyFnSig {
     let struct_data = db.struct_data(def);
     let fields = struct_data.variant_data.fields();
-    let resolver = def.resolver(db);
+    let resolver = def.resolver(db.upcast());
     let ctx =
         TyLoweringContext::new(db, &resolver).with_type_param_mode(TypeParamLoweringMode::Variable);
     let params =
@@ -819,21 +817,21 @@ fn fn_sig_for_struct_constructor(db: &impl HirDatabase, def: StructId) -> PolyFn
 }
 
 /// Build the type of a tuple struct constructor.
-fn type_for_struct_constructor(db: &impl HirDatabase, def: StructId) -> Binders<Ty> {
+fn type_for_struct_constructor(db: &dyn HirDatabase, def: StructId) -> Binders<Ty> {
     let struct_data = db.struct_data(def);
     if let StructKind::Unit = struct_data.variant_data.kind() {
         return type_for_adt(db, def.into());
     }
-    let generics = generics(db, def.into());
+    let generics = generics(db.upcast(), def.into());
     let substs = Substs::bound_vars(&generics);
     Binders::new(substs.len(), Ty::apply(TypeCtor::FnDef(def.into()), substs))
 }
 
-fn fn_sig_for_enum_variant_constructor(db: &impl HirDatabase, def: EnumVariantId) -> PolyFnSig {
+fn fn_sig_for_enum_variant_constructor(db: &dyn HirDatabase, def: EnumVariantId) -> PolyFnSig {
     let enum_data = db.enum_data(def.parent);
     let var_data = &enum_data.variants[def.local_id];
     let fields = var_data.variant_data.fields();
-    let resolver = def.parent.resolver(db);
+    let resolver = def.parent.resolver(db.upcast());
     let ctx =
         TyLoweringContext::new(db, &resolver).with_type_param_mode(TypeParamLoweringMode::Variable);
     let params =
@@ -843,26 +841,26 @@ fn fn_sig_for_enum_variant_constructor(db: &impl HirDatabase, def: EnumVariantId
 }
 
 /// Build the type of a tuple enum variant constructor.
-fn type_for_enum_variant_constructor(db: &impl HirDatabase, def: EnumVariantId) -> Binders<Ty> {
+fn type_for_enum_variant_constructor(db: &dyn HirDatabase, def: EnumVariantId) -> Binders<Ty> {
     let enum_data = db.enum_data(def.parent);
     let var_data = &enum_data.variants[def.local_id].variant_data;
     if let StructKind::Unit = var_data.kind() {
         return type_for_adt(db, def.parent.into());
     }
-    let generics = generics(db, def.parent.into());
+    let generics = generics(db.upcast(), def.parent.into());
     let substs = Substs::bound_vars(&generics);
     Binders::new(substs.len(), Ty::apply(TypeCtor::FnDef(def.into()), substs))
 }
 
-fn type_for_adt(db: &impl HirDatabase, adt: AdtId) -> Binders<Ty> {
-    let generics = generics(db, adt.into());
+fn type_for_adt(db: &dyn HirDatabase, adt: AdtId) -> Binders<Ty> {
+    let generics = generics(db.upcast(), adt.into());
     let substs = Substs::bound_vars(&generics);
     Binders::new(substs.len(), Ty::apply(TypeCtor::Adt(adt), substs))
 }
 
-fn type_for_type_alias(db: &impl HirDatabase, t: TypeAliasId) -> Binders<Ty> {
-    let generics = generics(db, t.into());
-    let resolver = t.resolver(db);
+fn type_for_type_alias(db: &dyn HirDatabase, t: TypeAliasId) -> Binders<Ty> {
+    let generics = generics(db.upcast(), t.into());
+    let resolver = t.resolver(db.upcast());
     let ctx =
         TyLoweringContext::new(db, &resolver).with_type_param_mode(TypeParamLoweringMode::Variable);
     let type_ref = &db.type_alias_data(t).type_ref;
@@ -880,7 +878,8 @@ pub enum CallableDef {
 impl_froms!(CallableDef: FunctionId, StructId, EnumVariantId);
 
 impl CallableDef {
-    pub fn krate(self, db: &impl HirDatabase) -> CrateId {
+    pub fn krate(self, db: &dyn HirDatabase) -> CrateId {
+        let db = db.upcast();
         match self {
             CallableDef::FunctionId(f) => f.lookup(db).module(db),
             CallableDef::StructId(s) => s.lookup(db).container.module(db),
@@ -922,7 +921,7 @@ impl_froms!(ValueTyDefId: FunctionId, StructId, EnumVariantId, ConstId, StaticId
 /// `struct Foo(usize)`, we have two types: The type of the struct itself, and
 /// the constructor function `(usize) -> Foo` which lives in the values
 /// namespace.
-pub(crate) fn ty_query(db: &impl HirDatabase, def: TyDefId) -> Binders<Ty> {
+pub(crate) fn ty_query(db: &dyn HirDatabase, def: TyDefId) -> Binders<Ty> {
     match def {
         TyDefId::BuiltinType(it) => Binders::new(0, type_for_builtin(it)),
         TyDefId::AdtId(it) => type_for_adt(db, it),
@@ -930,16 +929,16 @@ pub(crate) fn ty_query(db: &impl HirDatabase, def: TyDefId) -> Binders<Ty> {
     }
 }
 
-pub(crate) fn ty_recover(db: &impl HirDatabase, _cycle: &[String], def: &TyDefId) -> Binders<Ty> {
+pub(crate) fn ty_recover(db: &dyn HirDatabase, _cycle: &[String], def: &TyDefId) -> Binders<Ty> {
     let num_binders = match *def {
         TyDefId::BuiltinType(_) => 0,
-        TyDefId::AdtId(it) => generics(db, it.into()).len(),
-        TyDefId::TypeAliasId(it) => generics(db, it.into()).len(),
+        TyDefId::AdtId(it) => generics(db.upcast(), it.into()).len(),
+        TyDefId::TypeAliasId(it) => generics(db.upcast(), it.into()).len(),
     };
     Binders::new(num_binders, Ty::Unknown)
 }
 
-pub(crate) fn value_ty_query(db: &impl HirDatabase, def: ValueTyDefId) -> Binders<Ty> {
+pub(crate) fn value_ty_query(db: &dyn HirDatabase, def: ValueTyDefId) -> Binders<Ty> {
     match def {
         ValueTyDefId::FunctionId(it) => type_for_fn(db, it),
         ValueTyDefId::StructId(it) => type_for_struct_constructor(db, it),
@@ -949,30 +948,27 @@ pub(crate) fn value_ty_query(db: &impl HirDatabase, def: ValueTyDefId) -> Binder
     }
 }
 
-pub(crate) fn impl_self_ty_query(db: &impl HirDatabase, impl_id: ImplId) -> Binders<Ty> {
+pub(crate) fn impl_self_ty_query(db: &dyn HirDatabase, impl_id: ImplId) -> Binders<Ty> {
     let impl_data = db.impl_data(impl_id);
-    let resolver = impl_id.resolver(db);
-    let generics = generics(db, impl_id.into());
+    let resolver = impl_id.resolver(db.upcast());
+    let generics = generics(db.upcast(), impl_id.into());
     let ctx =
         TyLoweringContext::new(db, &resolver).with_type_param_mode(TypeParamLoweringMode::Variable);
     Binders::new(generics.len(), Ty::from_hir(&ctx, &impl_data.target_type))
 }
 
 pub(crate) fn impl_self_ty_recover(
-    db: &impl HirDatabase,
+    db: &dyn HirDatabase,
     _cycle: &[String],
     impl_id: &ImplId,
 ) -> Binders<Ty> {
-    let generics = generics(db, (*impl_id).into());
+    let generics = generics(db.upcast(), (*impl_id).into());
     Binders::new(generics.len(), Ty::Unknown)
 }
 
-pub(crate) fn impl_trait_query(
-    db: &impl HirDatabase,
-    impl_id: ImplId,
-) -> Option<Binders<TraitRef>> {
+pub(crate) fn impl_trait_query(db: &dyn HirDatabase, impl_id: ImplId) -> Option<Binders<TraitRef>> {
     let impl_data = db.impl_data(impl_id);
-    let resolver = impl_id.resolver(db);
+    let resolver = impl_id.resolver(db.upcast());
     let ctx =
         TyLoweringContext::new(db, &resolver).with_type_param_mode(TypeParamLoweringMode::Variable);
     let self_ty = db.impl_self_ty(impl_id);
diff --git a/crates/ra_hir_ty/src/method_resolution.rs b/crates/ra_hir_ty/src/method_resolution.rs
index 7f5e1469e..69c059ac8 100644
--- a/crates/ra_hir_ty/src/method_resolution.rs
+++ b/crates/ra_hir_ty/src/method_resolution.rs
@@ -48,10 +48,7 @@ pub struct CrateImplDefs {
 }
 
 impl CrateImplDefs {
-    pub(crate) fn impls_in_crate_query(
-        db: &impl HirDatabase,
-        krate: CrateId,
-    ) -> Arc<CrateImplDefs> {
+    pub(crate) fn impls_in_crate_query(db: &dyn HirDatabase, krate: CrateId) -> Arc<CrateImplDefs> {
         let _p = profile("impls_in_crate_query");
         let mut res =
             CrateImplDefs { impls: FxHashMap::default(), impls_by_trait: FxHashMap::default() };
@@ -92,7 +89,7 @@ impl CrateImplDefs {
 impl Ty {
     pub fn def_crates(
         &self,
-        db: &impl HirDatabase,
+        db: &dyn HirDatabase,
         cur_crate: CrateId,
     ) -> Option<ArrayVec<[CrateId; 2]>> {
         // Types like slice can have inherent impls in several crates, (core and alloc).
@@ -110,7 +107,7 @@ impl Ty {
         let lang_item_targets = match self {
             Ty::Apply(a_ty) => match a_ty.ctor {
                 TypeCtor::Adt(def_id) => {
-                    return Some(std::iter::once(def_id.module(db).krate).collect())
+                    return Some(std::iter::once(def_id.module(db.upcast()).krate).collect())
                 }
                 TypeCtor::Bool => lang_item_crate!("bool"),
                 TypeCtor::Char => lang_item_crate!("char"),
@@ -134,7 +131,7 @@ impl Ty {
                 LangItemTarget::ImplDefId(it) => Some(it),
                 _ => None,
             })
-            .map(|it| it.lookup(db).container.module(db).krate)
+            .map(|it| it.lookup(db.upcast()).container.module(db.upcast()).krate)
             .collect();
         Some(res)
     }
@@ -143,7 +140,7 @@ impl Ty {
 /// receiver type (but without autoref applied yet).
 pub(crate) fn lookup_method(
     ty: &Canonical<Ty>,
-    db: &impl HirDatabase,
+    db: &dyn HirDatabase,
     env: Arc<TraitEnvironment>,
     krate: CrateId,
     traits_in_scope: &FxHashSet<TraitId>,
@@ -181,7 +178,7 @@ pub enum LookupMode {
 // FIXME add a context type here?
 pub fn iterate_method_candidates<T>(
     ty: &Canonical<Ty>,
-    db: &impl HirDatabase,
+    db: &dyn HirDatabase,
     env: Arc<TraitEnvironment>,
     krate: CrateId,
     traits_in_scope: &FxHashSet<TraitId>,
@@ -247,7 +244,7 @@ pub fn iterate_method_candidates<T>(
 
 fn iterate_method_candidates_with_autoref<T>(
     deref_chain: &[Canonical<Ty>],
-    db: &impl HirDatabase,
+    db: &dyn HirDatabase,
     env: Arc<TraitEnvironment>,
     krate: CrateId,
     traits_in_scope: &FxHashSet<TraitId>,
@@ -304,7 +301,7 @@ fn iterate_method_candidates_with_autoref<T>(
 fn iterate_method_candidates_by_receiver<T>(
     receiver_ty: &Canonical<Ty>,
     rest_of_deref_chain: &[Canonical<Ty>],
-    db: &impl HirDatabase,
+    db: &dyn HirDatabase,
     env: Arc<TraitEnvironment>,
     krate: CrateId,
     traits_in_scope: &FxHashSet<TraitId>,
@@ -340,7 +337,7 @@ fn iterate_method_candidates_by_receiver<T>(
 
 fn iterate_method_candidates_for_self_ty<T>(
     self_ty: &Canonical<Ty>,
-    db: &impl HirDatabase,
+    db: &dyn HirDatabase,
     env: Arc<TraitEnvironment>,
     krate: CrateId,
     traits_in_scope: &FxHashSet<TraitId>,
@@ -367,7 +364,7 @@ fn iterate_method_candidates_for_self_ty<T>(
 
 fn iterate_trait_method_candidates<T>(
     self_ty: &Canonical<Ty>,
-    db: &impl HirDatabase,
+    db: &dyn HirDatabase,
     env: Arc<TraitEnvironment>,
     krate: CrateId,
     traits_in_scope: &FxHashSet<TraitId>,
@@ -381,7 +378,7 @@ fn iterate_trait_method_candidates<T>(
         // if we have `T: Trait` in the param env, the trait doesn't need to be in scope
         env.trait_predicates_for_self_ty(&self_ty.value)
             .map(|tr| tr.trait_)
-            .flat_map(|t| all_super_traits(db, t))
+            .flat_map(|t| all_super_traits(db.upcast(), t))
             .collect()
     } else {
         Vec::new()
@@ -416,7 +413,7 @@ fn iterate_trait_method_candidates<T>(
 
 fn iterate_inherent_methods<T>(
     self_ty: &Canonical<Ty>,
-    db: &impl HirDatabase,
+    db: &dyn HirDatabase,
     name: Option<&Name>,
     receiver_ty: Option<&Canonical<Ty>>,
     krate: CrateId,
@@ -449,7 +446,7 @@ fn iterate_inherent_methods<T>(
 
 /// Returns the self type for the index trait call.
 pub fn resolve_indexing_op(
-    db: &impl HirDatabase,
+    db: &dyn HirDatabase,
     ty: &Canonical<Ty>,
     env: Arc<TraitEnvironment>,
     krate: CrateId,
@@ -467,7 +464,7 @@ pub fn resolve_indexing_op(
 }
 
 fn is_valid_candidate(
-    db: &impl HirDatabase,
+    db: &dyn HirDatabase,
     name: Option<&Name>,
     receiver_ty: Option<&Canonical<Ty>>,
     item: AssocItemId,
@@ -504,7 +501,7 @@ fn is_valid_candidate(
 }
 
 pub(crate) fn inherent_impl_substs(
-    db: &impl HirDatabase,
+    db: &dyn HirDatabase,
     impl_id: ImplId,
     self_ty: &Canonical<Ty>,
 ) -> Option<Substs> {
@@ -544,11 +541,11 @@ fn fallback_bound_vars(s: Substs, num_vars_to_keep: usize) -> Substs {
 }
 
 fn transform_receiver_ty(
-    db: &impl HirDatabase,
+    db: &dyn HirDatabase,
     function_id: FunctionId,
     self_ty: &Canonical<Ty>,
 ) -> Option<Ty> {
-    let substs = match function_id.lookup(db).container {
+    let substs = match function_id.lookup(db.upcast()).container {
         AssocContainerId::TraitId(_) => Substs::build_for_def(db, function_id)
             .push(self_ty.value.clone())
             .fill_with_unknown()
@@ -562,7 +559,7 @@ fn transform_receiver_ty(
 
 pub fn implements_trait(
     ty: &Canonical<Ty>,
-    db: &impl HirDatabase,
+    db: &dyn HirDatabase,
     env: Arc<TraitEnvironment>,
     krate: CrateId,
     trait_: TraitId,
@@ -581,7 +578,7 @@ pub fn implements_trait(
 /// This creates Substs for a trait with the given Self type and type variables
 /// for all other parameters, to query Chalk with it.
 fn generic_implements_goal(
-    db: &impl HirDatabase,
+    db: &dyn HirDatabase,
     env: Arc<TraitEnvironment>,
     trait_: TraitId,
     self_ty: Canonical<Ty>,
@@ -598,7 +595,7 @@ fn generic_implements_goal(
 }
 
 fn autoderef_method_receiver(
-    db: &impl HirDatabase,
+    db: &dyn HirDatabase,
     krate: CrateId,
     ty: InEnvironment<Canonical<Ty>>,
 ) -> Vec<Canonical<Ty>> {
diff --git a/crates/ra_hir_ty/src/test_db.rs b/crates/ra_hir_ty/src/test_db.rs
index 0be2fea4b..5bbeabf51 100644
--- a/crates/ra_hir_ty/src/test_db.rs
+++ b/crates/ra_hir_ty/src/test_db.rs
@@ -6,8 +6,10 @@ use std::{
 };
 
 use hir_def::{db::DefDatabase, AssocItemId, ModuleDefId, ModuleId};
-use hir_expand::diagnostics::DiagnosticSink;
-use ra_db::{salsa, CrateId, FileId, FileLoader, FileLoaderDelegate, RelativePath, SourceDatabase};
+use hir_expand::{db::AstDatabase, diagnostics::DiagnosticSink};
+use ra_db::{
+    salsa, CrateId, FileId, FileLoader, FileLoaderDelegate, RelativePath, SourceDatabase, Upcast,
+};
 
 use crate::{db::HirDatabase, expr::ExprValidator};
 
@@ -25,6 +27,18 @@ pub struct TestDB {
     runtime: salsa::Runtime<TestDB>,
 }
 
+impl Upcast<dyn AstDatabase> for TestDB {
+    fn upcast(&self) -> &(dyn AstDatabase + 'static) {
+        &*self
+    }
+}
+
+impl Upcast<dyn DefDatabase> for TestDB {
+    fn upcast(&self) -> &(dyn DefDatabase + 'static) {
+        &*self
+    }
+}
+
 impl salsa::Database for TestDB {
     fn salsa_runtime(&self) -> &salsa::Runtime<TestDB> {
         &self.runtime
diff --git a/crates/ra_hir_ty/src/traits.rs b/crates/ra_hir_ty/src/traits.rs
index 6e1c8e42a..a1ca33c98 100644
--- a/crates/ra_hir_ty/src/traits.rs
+++ b/crates/ra_hir_ty/src/traits.rs
@@ -24,8 +24,8 @@ const CHALK_SOLVER_MAX_SIZE: usize = 10;
 const CHALK_SOLVER_FUEL: i32 = 100;
 
 #[derive(Debug, Copy, Clone)]
-struct ChalkContext<'a, DB> {
-    db: &'a DB,
+struct ChalkContext<'a> {
+    db: &'a dyn HirDatabase,
     krate: CrateId,
 }
 
@@ -37,7 +37,7 @@ fn create_chalk_solver() -> chalk_solve::Solver<Interner> {
 
 /// Collects impls for the given trait in the whole dependency tree of `krate`.
 pub(crate) fn impls_for_trait_query(
-    db: &impl HirDatabase,
+    db: &dyn HirDatabase,
     krate: CrateId,
     trait_: TraitId,
 ) -> Arc<[ImplId]> {
@@ -136,7 +136,7 @@ impl TypeWalk for ProjectionPredicate {
 
 /// Solve a trait goal using Chalk.
 pub(crate) fn trait_solve_query(
-    db: &impl HirDatabase,
+    db: &dyn HirDatabase,
     krate: CrateId,
     goal: Canonical<InEnvironment<Obligation>>,
 ) -> Option<Solution> {
@@ -163,7 +163,7 @@ pub(crate) fn trait_solve_query(
 }
 
 fn solve(
-    db: &impl HirDatabase,
+    db: &dyn HirDatabase,
     krate: CrateId,
     goal: &chalk_ir::UCanonical<chalk_ir::InEnvironment<chalk_ir::Goal<Interner>>>,
 ) -> Option<chalk_solve::Solution<Interner>> {
@@ -188,7 +188,7 @@ fn solve(
 }
 
 fn solution_from_chalk(
-    db: &impl HirDatabase,
+    db: &dyn HirDatabase,
     solution: chalk_solve::Solution<Interner>,
 ) -> Solution {
     let convert_subst = |subst: chalk_ir::Canonical<chalk_ir::Substitution<Interner>>| {
diff --git a/crates/ra_hir_ty/src/traits/builtin.rs b/crates/ra_hir_ty/src/traits/builtin.rs
index 03f9b4e27..73e3c5c78 100644
--- a/crates/ra_hir_ty/src/traits/builtin.rs
+++ b/crates/ra_hir_ty/src/traits/builtin.rs
@@ -26,7 +26,7 @@ pub(super) struct BuiltinImplAssocTyValueData {
 }
 
 pub(super) fn get_builtin_impls(
-    db: &impl HirDatabase,
+    db: &dyn HirDatabase,
     krate: CrateId,
     ty: &Ty,
     // The first argument for the trait, if present
@@ -59,7 +59,7 @@ pub(super) fn get_builtin_impls(
 }
 
 fn get_builtin_unsize_impls(
-    db: &impl HirDatabase,
+    db: &dyn HirDatabase,
     krate: CrateId,
     ty: &Ty,
     // The first argument for the trait, if present
@@ -79,7 +79,7 @@ fn get_builtin_unsize_impls(
         // FIXME what about more complicated dyn tys with marker traits?
         if let Some(trait_ref) = ty.dyn_trait_ref() {
             if trait_ref.trait_ != target_trait.trait_ {
-                let super_traits = all_super_traits(db, trait_ref.trait_);
+                let super_traits = all_super_traits(db.upcast(), trait_ref.trait_);
                 if super_traits.contains(&target_trait.trait_) {
                     callback(Impl::UnsizeToSuperTraitObject(UnsizeToSuperTraitObjectData {
                         trait_: trait_ref.trait_,
@@ -94,7 +94,7 @@ fn get_builtin_unsize_impls(
     }
 }
 
-pub(super) fn impl_datum(db: &impl HirDatabase, krate: CrateId, impl_: Impl) -> BuiltinImplData {
+pub(super) fn impl_datum(db: &dyn HirDatabase, krate: CrateId, impl_: Impl) -> BuiltinImplData {
     match impl_ {
         Impl::ImplDef(_) => unreachable!(),
         Impl::ClosureFnTraitImpl(data) => closure_fn_trait_impl_datum(db, krate, data),
@@ -107,7 +107,7 @@ pub(super) fn impl_datum(db: &impl HirDatabase, krate: CrateId, impl_: Impl) ->
 }
 
 pub(super) fn associated_ty_value(
-    db: &impl HirDatabase,
+    db: &dyn HirDatabase,
     krate: CrateId,
     data: AssocTyValue,
 ) -> BuiltinImplAssocTyValueData {
@@ -122,7 +122,7 @@ pub(super) fn associated_ty_value(
 // Closure Fn trait impls
 
 fn check_closure_fn_trait_impl_prerequisites(
-    db: &impl HirDatabase,
+    db: &dyn HirDatabase,
     krate: CrateId,
     data: super::ClosureFnTraitImplData,
 ) -> bool {
@@ -143,7 +143,7 @@ fn check_closure_fn_trait_impl_prerequisites(
 }
 
 fn closure_fn_trait_impl_datum(
-    db: &impl HirDatabase,
+    db: &dyn HirDatabase,
     krate: CrateId,
     data: super::ClosureFnTraitImplData,
 ) -> BuiltinImplData {
@@ -189,7 +189,7 @@ fn closure_fn_trait_impl_datum(
 }
 
 fn closure_fn_trait_output_assoc_ty_value(
-    db: &impl HirDatabase,
+    db: &dyn HirDatabase,
     krate: CrateId,
     data: super::ClosureFnTraitImplData,
 ) -> BuiltinImplAssocTyValueData {
@@ -223,17 +223,17 @@ fn closure_fn_trait_output_assoc_ty_value(
 
 // Array unsizing
 
-fn check_unsize_impl_prerequisites(db: &impl HirDatabase, krate: CrateId) -> bool {
+fn check_unsize_impl_prerequisites(db: &dyn HirDatabase, krate: CrateId) -> bool {
     // the Unsize trait needs to exist and have two type parameters (Self and T)
     let unsize_trait = match get_unsize_trait(db, krate) {
         Some(t) => t,
         None => return false,
     };
-    let generic_params = generics(db, unsize_trait.into());
+    let generic_params = generics(db.upcast(), unsize_trait.into());
     generic_params.len() == 2
 }
 
-fn array_unsize_impl_datum(db: &impl HirDatabase, krate: CrateId) -> BuiltinImplData {
+fn array_unsize_impl_datum(db: &dyn HirDatabase, krate: CrateId) -> BuiltinImplData {
     // impl<T> Unsize<[T]> for [T; _]
     // (this can be a single impl because we don't distinguish array sizes currently)
 
@@ -260,7 +260,7 @@ fn array_unsize_impl_datum(db: &impl HirDatabase, krate: CrateId) -> BuiltinImpl
 // Trait object unsizing
 
 fn trait_object_unsize_impl_datum(
-    db: &impl HirDatabase,
+    db: &dyn HirDatabase,
     krate: CrateId,
     trait_: TraitId,
 ) -> BuiltinImplData {
@@ -295,7 +295,7 @@ fn trait_object_unsize_impl_datum(
 }
 
 fn super_trait_object_unsize_impl_datum(
-    db: &impl HirDatabase,
+    db: &dyn HirDatabase,
     krate: CrateId,
     data: UnsizeToSuperTraitObjectData,
 ) -> BuiltinImplData {
@@ -313,7 +313,7 @@ fn super_trait_object_unsize_impl_datum(
     let self_bounds = vec![GenericPredicate::Implemented(self_trait_ref.clone())];
 
     // we need to go from our trait to the super trait, substituting type parameters
-    let path = crate::utils::find_super_trait_path(db, data.trait_, data.super_trait);
+    let path = crate::utils::find_super_trait_path(db.upcast(), data.trait_, data.super_trait);
 
     let mut current_trait_ref = self_trait_ref;
     for t in path.into_iter().skip(1) {
@@ -344,11 +344,7 @@ fn super_trait_object_unsize_impl_datum(
     BuiltinImplData { num_vars, trait_ref, where_clauses: Vec::new(), assoc_ty_values: Vec::new() }
 }
 
-fn get_fn_trait(
-    db: &impl HirDatabase,
-    krate: CrateId,
-    fn_trait: super::FnTrait,
-) -> Option<TraitId> {
+fn get_fn_trait(db: &dyn HirDatabase, krate: CrateId, fn_trait: super::FnTrait) -> Option<TraitId> {
     let target = db.lang_item(krate, fn_trait.lang_item_name().into())?;
     match target {
         LangItemTarget::TraitId(t) => Some(t),
@@ -356,7 +352,7 @@ fn get_fn_trait(
     }
 }
 
-fn get_unsize_trait(db: &impl HirDatabase, krate: CrateId) -> Option<TraitId> {
+fn get_unsize_trait(db: &dyn HirDatabase, krate: CrateId) -> Option<TraitId> {
     let target = db.lang_item(krate, "unsize".into())?;
     match target {
         LangItemTarget::TraitId(t) => Some(t),
diff --git a/crates/ra_hir_ty/src/traits/chalk.rs b/crates/ra_hir_ty/src/traits/chalk.rs
index 62509bc29..943d5f125 100644
--- a/crates/ra_hir_ty/src/traits/chalk.rs
+++ b/crates/ra_hir_ty/src/traits/chalk.rs
@@ -127,11 +127,11 @@ pub type AssociatedTyValue = chalk_rust_ir::AssociatedTyValue<Interner>;
 
 pub(super) trait ToChalk {
     type Chalk;
-    fn to_chalk(self, db: &impl HirDatabase) -> Self::Chalk;
-    fn from_chalk(db: &impl HirDatabase, chalk: Self::Chalk) -> Self;
+    fn to_chalk(self, db: &dyn HirDatabase) -> Self::Chalk;
+    fn from_chalk(db: &dyn HirDatabase, chalk: Self::Chalk) -> Self;
 }
 
-pub(super) fn from_chalk<T, ChalkT>(db: &impl HirDatabase, chalk: ChalkT) -> T
+pub(super) fn from_chalk<T, ChalkT>(db: &dyn HirDatabase, chalk: ChalkT) -> T
 where
     T: ToChalk<Chalk = ChalkT>,
 {
@@ -140,7 +140,7 @@ where
 
 impl ToChalk for Ty {
     type Chalk = chalk_ir::Ty<Interner>;
-    fn to_chalk(self, db: &impl HirDatabase) -> chalk_ir::Ty<Interner> {
+    fn to_chalk(self, db: &dyn HirDatabase) -> chalk_ir::Ty<Interner> {
         match self {
             Ty::Apply(apply_ty) => {
                 let name = apply_ty.ctor.to_chalk(db);
@@ -179,7 +179,7 @@ impl ToChalk for Ty {
             }
         }
     }
-    fn from_chalk(db: &impl HirDatabase, chalk: chalk_ir::Ty<Interner>) -> Self {
+    fn from_chalk(db: &dyn HirDatabase, chalk: chalk_ir::Ty<Interner>) -> Self {
         match chalk.data().clone() {
             chalk_ir::TyData::Apply(apply_ty) => match apply_ty.name {
                 TypeName::Error => Ty::Unknown,
@@ -217,11 +217,11 @@ impl ToChalk for Ty {
 impl ToChalk for Substs {
     type Chalk = chalk_ir::Substitution<Interner>;
 
-    fn to_chalk(self, db: &impl HirDatabase) -> chalk_ir::Substitution<Interner> {
+    fn to_chalk(self, db: &dyn HirDatabase) -> chalk_ir::Substitution<Interner> {
         chalk_ir::Substitution::from(self.iter().map(|ty| ty.clone().to_chalk(db)))
     }
 
-    fn from_chalk(db: &impl HirDatabase, parameters: chalk_ir::Substitution<Interner>) -> Substs {
+    fn from_chalk(db: &dyn HirDatabase, parameters: chalk_ir::Substitution<Interner>) -> Substs {
         let tys = parameters
             .into_iter()
             .map(|p| match p.ty() {
@@ -236,13 +236,13 @@ impl ToChalk for Substs {
 impl ToChalk for TraitRef {
     type Chalk = chalk_ir::TraitRef<Interner>;
 
-    fn to_chalk(self: TraitRef, db: &impl HirDatabase) -> chalk_ir::TraitRef<Interner> {
+    fn to_chalk(self: TraitRef, db: &dyn HirDatabase) -> chalk_ir::TraitRef<Interner> {
         let trait_id = self.trait_.to_chalk(db);
         let substitution = self.substs.to_chalk(db);
         chalk_ir::TraitRef { trait_id, substitution }
     }
 
-    fn from_chalk(db: &impl HirDatabase, trait_ref: chalk_ir::TraitRef<Interner>) -> Self {
+    fn from_chalk(db: &dyn HirDatabase, trait_ref: chalk_ir::TraitRef<Interner>) -> Self {
         let trait_ = from_chalk(db, trait_ref.trait_id);
         let substs = from_chalk(db, trait_ref.substitution);
         TraitRef { trait_, substs }
@@ -252,11 +252,11 @@ impl ToChalk for TraitRef {
 impl ToChalk for hir_def::TraitId {
     type Chalk = TraitId;
 
-    fn to_chalk(self, _db: &impl HirDatabase) -> TraitId {
+    fn to_chalk(self, _db: &dyn HirDatabase) -> TraitId {
         chalk_ir::TraitId(self.as_intern_id())
     }
 
-    fn from_chalk(_db: &impl HirDatabase, trait_id: TraitId) -> hir_def::TraitId {
+    fn from_chalk(_db: &dyn HirDatabase, trait_id: TraitId) -> hir_def::TraitId {
         InternKey::from_intern_id(trait_id.0)
     }
 }
@@ -264,7 +264,7 @@ impl ToChalk for hir_def::TraitId {
 impl ToChalk for TypeCtor {
     type Chalk = TypeName<Interner>;
 
-    fn to_chalk(self, db: &impl HirDatabase) -> TypeName<Interner> {
+    fn to_chalk(self, db: &dyn HirDatabase) -> TypeName<Interner> {
         match self {
             TypeCtor::AssociatedType(type_alias) => {
                 let type_id = type_alias.to_chalk(db);
@@ -278,7 +278,7 @@ impl ToChalk for TypeCtor {
         }
     }
 
-    fn from_chalk(db: &impl HirDatabase, type_name: TypeName<Interner>) -> TypeCtor {
+    fn from_chalk(db: &dyn HirDatabase, type_name: TypeName<Interner>) -> TypeCtor {
         match type_name {
             TypeName::Struct(struct_id) => db.lookup_intern_type_ctor(struct_id.into()),
             TypeName::AssociatedType(type_id) => TypeCtor::AssociatedType(from_chalk(db, type_id)),
@@ -293,11 +293,11 @@ impl ToChalk for TypeCtor {
 impl ToChalk for Impl {
     type Chalk = ImplId;
 
-    fn to_chalk(self, db: &impl HirDatabase) -> ImplId {
+    fn to_chalk(self, db: &dyn HirDatabase) -> ImplId {
         db.intern_chalk_impl(self).into()
     }
 
-    fn from_chalk(db: &impl HirDatabase, impl_id: ImplId) -> Impl {
+    fn from_chalk(db: &dyn HirDatabase, impl_id: ImplId) -> Impl {
         db.lookup_intern_chalk_impl(impl_id.into())
     }
 }
@@ -305,11 +305,11 @@ impl ToChalk for Impl {
 impl ToChalk for TypeAliasId {
     type Chalk = AssocTypeId;
 
-    fn to_chalk(self, _db: &impl HirDatabase) -> AssocTypeId {
+    fn to_chalk(self, _db: &dyn HirDatabase) -> AssocTypeId {
         chalk_ir::AssocTypeId(self.as_intern_id())
     }
 
-    fn from_chalk(_db: &impl HirDatabase, type_alias_id: AssocTypeId) -> TypeAliasId {
+    fn from_chalk(_db: &dyn HirDatabase, type_alias_id: AssocTypeId) -> TypeAliasId {
         InternKey::from_intern_id(type_alias_id.0)
     }
 }
@@ -317,11 +317,11 @@ impl ToChalk for TypeAliasId {
 impl ToChalk for AssocTyValue {
     type Chalk = AssociatedTyValueId;
 
-    fn to_chalk(self, db: &impl HirDatabase) -> AssociatedTyValueId {
+    fn to_chalk(self, db: &dyn HirDatabase) -> AssociatedTyValueId {
         db.intern_assoc_ty_value(self).into()
     }
 
-    fn from_chalk(db: &impl HirDatabase, assoc_ty_value_id: AssociatedTyValueId) -> AssocTyValue {
+    fn from_chalk(db: &dyn HirDatabase, assoc_ty_value_id: AssociatedTyValueId) -> AssocTyValue {
         db.lookup_intern_assoc_ty_value(assoc_ty_value_id.into())
     }
 }
@@ -329,7 +329,7 @@ impl ToChalk for AssocTyValue {
 impl ToChalk for GenericPredicate {
     type Chalk = chalk_ir::QuantifiedWhereClause<Interner>;
 
-    fn to_chalk(self, db: &impl HirDatabase) -> chalk_ir::QuantifiedWhereClause<Interner> {
+    fn to_chalk(self, db: &dyn HirDatabase) -> chalk_ir::QuantifiedWhereClause<Interner> {
         match self {
             GenericPredicate::Implemented(trait_ref) => {
                 make_binders(chalk_ir::WhereClause::Implemented(trait_ref.to_chalk(db)), 0)
@@ -346,7 +346,7 @@ impl ToChalk for GenericPredicate {
     }
 
     fn from_chalk(
-        db: &impl HirDatabase,
+        db: &dyn HirDatabase,
         where_clause: chalk_ir::QuantifiedWhereClause<Interner>,
     ) -> GenericPredicate {
         match where_clause.value {
@@ -365,7 +365,7 @@ impl ToChalk for GenericPredicate {
 impl ToChalk for ProjectionTy {
     type Chalk = chalk_ir::AliasTy<Interner>;
 
-    fn to_chalk(self, db: &impl HirDatabase) -> chalk_ir::AliasTy<Interner> {
+    fn to_chalk(self, db: &dyn HirDatabase) -> chalk_ir::AliasTy<Interner> {
         chalk_ir::AliasTy {
             associated_ty_id: self.associated_ty.to_chalk(db),
             substitution: self.parameters.to_chalk(db),
@@ -373,7 +373,7 @@ impl ToChalk for ProjectionTy {
     }
 
     fn from_chalk(
-        db: &impl HirDatabase,
+        db: &dyn HirDatabase,
         projection_ty: chalk_ir::AliasTy<Interner>,
     ) -> ProjectionTy {
         ProjectionTy {
@@ -386,11 +386,11 @@ impl ToChalk for ProjectionTy {
 impl ToChalk for super::ProjectionPredicate {
     type Chalk = chalk_ir::Normalize<Interner>;
 
-    fn to_chalk(self, db: &impl HirDatabase) -> chalk_ir::Normalize<Interner> {
+    fn to_chalk(self, db: &dyn HirDatabase) -> chalk_ir::Normalize<Interner> {
         chalk_ir::Normalize { alias: self.projection_ty.to_chalk(db), ty: self.ty.to_chalk(db) }
     }
 
-    fn from_chalk(_db: &impl HirDatabase, _normalize: chalk_ir::Normalize<Interner>) -> Self {
+    fn from_chalk(_db: &dyn HirDatabase, _normalize: chalk_ir::Normalize<Interner>) -> Self {
         unimplemented!()
     }
 }
@@ -398,14 +398,14 @@ impl ToChalk for super::ProjectionPredicate {
 impl ToChalk for Obligation {
     type Chalk = chalk_ir::DomainGoal<Interner>;
 
-    fn to_chalk(self, db: &impl HirDatabase) -> chalk_ir::DomainGoal<Interner> {
+    fn to_chalk(self, db: &dyn HirDatabase) -> chalk_ir::DomainGoal<Interner> {
         match self {
             Obligation::Trait(tr) => tr.to_chalk(db).cast(),
             Obligation::Projection(pr) => pr.to_chalk(db).cast(),
         }
     }
 
-    fn from_chalk(_db: &impl HirDatabase, _goal: chalk_ir::DomainGoal<Interner>) -> Self {
+    fn from_chalk(_db: &dyn HirDatabase, _goal: chalk_ir::DomainGoal<Interner>) -> Self {
         unimplemented!()
     }
 }
@@ -416,13 +416,13 @@ where
 {
     type Chalk = chalk_ir::Canonical<T::Chalk>;
 
-    fn to_chalk(self, db: &impl HirDatabase) -> chalk_ir::Canonical<T::Chalk> {
+    fn to_chalk(self, db: &dyn HirDatabase) -> chalk_ir::Canonical<T::Chalk> {
         let parameter = chalk_ir::ParameterKind::Ty(chalk_ir::UniverseIndex::ROOT);
         let value = self.value.to_chalk(db);
         chalk_ir::Canonical { value, binders: vec![parameter; self.num_vars] }
     }
 
-    fn from_chalk(db: &impl HirDatabase, canonical: chalk_ir::Canonical<T::Chalk>) -> Canonical<T> {
+    fn from_chalk(db: &dyn HirDatabase, canonical: chalk_ir::Canonical<T::Chalk>) -> Canonical<T> {
         Canonical { num_vars: canonical.binders.len(), value: from_chalk(db, canonical.value) }
     }
 }
@@ -430,7 +430,7 @@ where
 impl ToChalk for Arc<super::TraitEnvironment> {
     type Chalk = chalk_ir::Environment<Interner>;
 
-    fn to_chalk(self, db: &impl HirDatabase) -> chalk_ir::Environment<Interner> {
+    fn to_chalk(self, db: &dyn HirDatabase) -> chalk_ir::Environment<Interner> {
         let mut clauses = Vec::new();
         for pred in &self.predicates {
             if pred.is_error() {
@@ -445,7 +445,7 @@ impl ToChalk for Arc<super::TraitEnvironment> {
     }
 
     fn from_chalk(
-        _db: &impl HirDatabase,
+        _db: &dyn HirDatabase,
         _env: chalk_ir::Environment<Interner>,
     ) -> Arc<super::TraitEnvironment> {
         unimplemented!()
@@ -458,7 +458,7 @@ where
 {
     type Chalk = chalk_ir::InEnvironment<T::Chalk>;
 
-    fn to_chalk(self, db: &impl HirDatabase) -> chalk_ir::InEnvironment<T::Chalk> {
+    fn to_chalk(self, db: &dyn HirDatabase) -> chalk_ir::InEnvironment<T::Chalk> {
         chalk_ir::InEnvironment {
             environment: self.environment.to_chalk(db),
             goal: self.value.to_chalk(db),
@@ -466,7 +466,7 @@ where
     }
 
     fn from_chalk(
-        db: &impl HirDatabase,
+        db: &dyn HirDatabase,
         in_env: chalk_ir::InEnvironment<T::Chalk>,
     ) -> super::InEnvironment<T> {
         super::InEnvironment {
@@ -479,7 +479,7 @@ where
 impl ToChalk for builtin::BuiltinImplData {
     type Chalk = ImplDatum;
 
-    fn to_chalk(self, db: &impl HirDatabase) -> ImplDatum {
+    fn to_chalk(self, db: &dyn HirDatabase) -> ImplDatum {
         let impl_type = chalk_rust_ir::ImplType::External;
         let where_clauses = self.where_clauses.into_iter().map(|w| w.to_chalk(db)).collect();
 
@@ -495,7 +495,7 @@ impl ToChalk for builtin::BuiltinImplData {
         }
     }
 
-    fn from_chalk(_db: &impl HirDatabase, _data: ImplDatum) -> Self {
+    fn from_chalk(_db: &dyn HirDatabase, _data: ImplDatum) -> Self {
         unimplemented!()
     }
 }
@@ -503,7 +503,7 @@ impl ToChalk for builtin::BuiltinImplData {
 impl ToChalk for builtin::BuiltinImplAssocTyValueData {
     type Chalk = AssociatedTyValue;
 
-    fn to_chalk(self, db: &impl HirDatabase) -> AssociatedTyValue {
+    fn to_chalk(self, db: &dyn HirDatabase) -> AssociatedTyValue {
         let value_bound = chalk_rust_ir::AssociatedTyValueBound { ty: self.value.to_chalk(db) };
 
         chalk_rust_ir::AssociatedTyValue {
@@ -514,7 +514,7 @@ impl ToChalk for builtin::BuiltinImplAssocTyValueData {
     }
 
     fn from_chalk(
-        _db: &impl HirDatabase,
+        _db: &dyn HirDatabase,
         _data: AssociatedTyValue,
     ) -> builtin::BuiltinImplAssocTyValueData {
         unimplemented!()
@@ -529,7 +529,7 @@ fn make_binders<T>(value: T, num_vars: usize) -> chalk_ir::Binders<T> {
 }
 
 fn convert_where_clauses(
-    db: &impl HirDatabase,
+    db: &dyn HirDatabase,
     def: GenericDefId,
     substs: &Substs,
 ) -> Vec<chalk_ir::QuantifiedWhereClause<Interner>> {
@@ -545,10 +545,7 @@ fn convert_where_clauses(
     result
 }
 
-impl<'a, DB> chalk_solve::RustIrDatabase<Interner> for ChalkContext<'a, DB>
-where
-    DB: HirDatabase,
-{
+impl<'a> chalk_solve::RustIrDatabase<Interner> for ChalkContext<'a> {
     fn associated_ty_data(&self, id: AssocTypeId) -> Arc<AssociatedTyDatum> {
         self.db.associated_ty_data(id)
     }
@@ -618,16 +615,16 @@ where
 }
 
 pub(crate) fn associated_ty_data_query(
-    db: &impl HirDatabase,
+    db: &dyn HirDatabase,
     id: AssocTypeId,
 ) -> Arc<AssociatedTyDatum> {
     debug!("associated_ty_data {:?}", id);
     let type_alias: TypeAliasId = from_chalk(db, id);
-    let trait_ = match type_alias.lookup(db).container {
+    let trait_ = match type_alias.lookup(db.upcast()).container {
         AssocContainerId::TraitId(t) => t,
         _ => panic!("associated type not in trait"),
     };
-    let generic_params = generics(db, type_alias.into());
+    let generic_params = generics(db.upcast(), type_alias.into());
     let bound_data = chalk_rust_ir::AssociatedTyDatumBound {
         // FIXME add bounds and where clauses
         bounds: vec![],
@@ -643,7 +640,7 @@ pub(crate) fn associated_ty_data_query(
 }
 
 pub(crate) fn trait_datum_query(
-    db: &impl HirDatabase,
+    db: &dyn HirDatabase,
     krate: CrateId,
     trait_id: TraitId,
 ) -> Arc<TraitDatum> {
@@ -651,11 +648,11 @@ pub(crate) fn trait_datum_query(
     let trait_: hir_def::TraitId = from_chalk(db, trait_id);
     let trait_data = db.trait_data(trait_);
     debug!("trait {:?} = {:?}", trait_id, trait_data.name);
-    let generic_params = generics(db, trait_.into());
+    let generic_params = generics(db.upcast(), trait_.into());
     let bound_vars = Substs::bound_vars(&generic_params);
     let flags = chalk_rust_ir::TraitFlags {
         auto: trait_data.auto,
-        upstream: trait_.lookup(db).container.module(db).krate != krate,
+        upstream: trait_.lookup(db.upcast()).container.module(db.upcast()).krate != krate,
         non_enumerable: true,
         coinductive: false, // only relevant for Chalk testing
         // FIXME set these flags correctly
@@ -676,7 +673,7 @@ pub(crate) fn trait_datum_query(
 }
 
 pub(crate) fn struct_datum_query(
-    db: &impl HirDatabase,
+    db: &dyn HirDatabase,
     krate: CrateId,
     struct_id: StructId,
 ) -> Arc<StructDatum> {
@@ -688,7 +685,7 @@ pub(crate) fn struct_datum_query(
     let where_clauses = type_ctor
         .as_generic_def()
         .map(|generic_def| {
-            let generic_params = generics(db, generic_def);
+            let generic_params = generics(db.upcast(), generic_def);
             let bound_vars = Substs::bound_vars(&generic_params);
             convert_where_clauses(db, generic_def, &bound_vars)
         })
@@ -708,7 +705,7 @@ pub(crate) fn struct_datum_query(
 }
 
 pub(crate) fn impl_datum_query(
-    db: &impl HirDatabase,
+    db: &dyn HirDatabase,
     krate: CrateId,
     impl_id: ImplId,
 ) -> Arc<ImplDatum> {
@@ -722,7 +719,7 @@ pub(crate) fn impl_datum_query(
 }
 
 fn impl_def_datum(
-    db: &impl HirDatabase,
+    db: &dyn HirDatabase,
     krate: CrateId,
     chalk_id: ImplId,
     impl_id: hir_def::ImplId,
@@ -734,10 +731,10 @@ fn impl_def_datum(
         .value;
     let impl_data = db.impl_data(impl_id);
 
-    let generic_params = generics(db, impl_id.into());
+    let generic_params = generics(db.upcast(), impl_id.into());
     let bound_vars = Substs::bound_vars(&generic_params);
     let trait_ = trait_ref.trait_;
-    let impl_type = if impl_id.lookup(db).container.module(db).krate == krate {
+    let impl_type = if impl_id.lookup(db.upcast()).container.module(db.upcast()).krate == krate {
         chalk_rust_ir::ImplType::Local
     } else {
         chalk_rust_ir::ImplType::External
@@ -786,7 +783,7 @@ fn impl_def_datum(
 }
 
 pub(crate) fn associated_ty_value_query(
-    db: &impl HirDatabase,
+    db: &dyn HirDatabase,
     krate: CrateId,
     id: AssociatedTyValueId,
 ) -> Arc<AssociatedTyValue> {
@@ -800,12 +797,12 @@ pub(crate) fn associated_ty_value_query(
 }
 
 fn type_alias_associated_ty_value(
-    db: &impl HirDatabase,
+    db: &dyn HirDatabase,
     _krate: CrateId,
     type_alias: TypeAliasId,
 ) -> Arc<AssociatedTyValue> {
     let type_alias_data = db.type_alias_data(type_alias);
-    let impl_id = match type_alias.lookup(db).container {
+    let impl_id = match type_alias.lookup(db.upcast()).container {
         AssocContainerId::ImplId(it) => it,
         _ => panic!("assoc ty value should be in impl"),
     };
diff --git a/crates/ra_hir_ty/src/utils.rs b/crates/ra_hir_ty/src/utils.rs
index 463fd65b4..b40d4eb73 100644
--- a/crates/ra_hir_ty/src/utils.rs
+++ b/crates/ra_hir_ty/src/utils.rs
@@ -14,7 +14,7 @@ use hir_def::{
 };
 use hir_expand::name::{name, Name};
 
-fn direct_super_traits(db: &impl DefDatabase, trait_: TraitId) -> Vec<TraitId> {
+fn direct_super_traits(db: &dyn DefDatabase, trait_: TraitId) -> Vec<TraitId> {
     let resolver = trait_.resolver(db);
     // returning the iterator directly doesn't easily work because of
     // lifetime problems, but since there usually shouldn't be more than a
@@ -43,7 +43,7 @@ fn direct_super_traits(db: &impl DefDatabase, trait_: TraitId) -> Vec<TraitId> {
 
 /// Returns an iterator over the whole super trait hierarchy (including the
 /// trait itself).
-pub(super) fn all_super_traits(db: &impl DefDatabase, trait_: TraitId) -> Vec<TraitId> {
+pub(super) fn all_super_traits(db: &dyn DefDatabase, trait_: TraitId) -> Vec<TraitId> {
     // we need to take care a bit here to avoid infinite loops in case of cycles
     // (i.e. if we have `trait A: B; trait B: A;`)
     let mut result = vec![trait_];
@@ -65,7 +65,7 @@ pub(super) fn all_super_traits(db: &impl DefDatabase, trait_: TraitId) -> Vec<Tr
 /// Finds a path from a trait to one of its super traits. Returns an empty
 /// vector if there is no path.
 pub(super) fn find_super_trait_path(
-    db: &impl DefDatabase,
+    db: &dyn DefDatabase,
     trait_: TraitId,
     super_trait: TraitId,
 ) -> Vec<TraitId> {
@@ -73,7 +73,7 @@ pub(super) fn find_super_trait_path(
     result.push(trait_);
     return if go(db, super_trait, &mut result) { result } else { Vec::new() };
 
-    fn go(db: &impl DefDatabase, super_trait: TraitId, path: &mut Vec<TraitId>) -> bool {
+    fn go(db: &dyn DefDatabase, super_trait: TraitId, path: &mut Vec<TraitId>) -> bool {
         let trait_ = *path.last().unwrap();
         if trait_ == super_trait {
             return true;
@@ -95,7 +95,7 @@ pub(super) fn find_super_trait_path(
 }
 
 pub(super) fn associated_type_by_name_including_super_traits(
-    db: &impl DefDatabase,
+    db: &dyn DefDatabase,
     trait_: TraitId,
     name: &Name,
 ) -> Option<TypeAliasId> {
@@ -104,7 +104,7 @@ pub(super) fn associated_type_by_name_including_super_traits(
         .find_map(|t| db.trait_data(t).associated_type_by_name(name))
 }
 
-pub(super) fn variant_data(db: &impl DefDatabase, var: VariantId) -> Arc<VariantData> {
+pub(super) fn variant_data(db: &dyn DefDatabase, var: VariantId) -> Arc<VariantData> {
     match var {
         VariantId::StructId(it) => db.struct_data(it).variant_data.clone(),
         VariantId::UnionId(it) => db.union_data(it).variant_data.clone(),
@@ -123,7 +123,7 @@ pub(crate) fn make_mut_slice<T: Clone>(a: &mut Arc<[T]>) -> &mut [T] {
     Arc::get_mut(a).unwrap()
 }
 
-pub(crate) fn generics(db: &impl DefDatabase, def: GenericDefId) -> Generics {
+pub(crate) fn generics(db: &dyn DefDatabase, def: GenericDefId) -> Generics {
     let parent_generics = parent_generic_def(db, def).map(|def| Box::new(generics(db, def)));
     Generics { def, params: db.generic_params(def), parent_generics }
 }
@@ -222,7 +222,7 @@ impl Generics {
     }
 }
 
-fn parent_generic_def(db: &impl DefDatabase, def: GenericDefId) -> Option<GenericDefId> {
+fn parent_generic_def(db: &dyn DefDatabase, def: GenericDefId) -> Option<GenericDefId> {
     let container = match def {
         GenericDefId::FunctionId(it) => it.lookup(db).container,
         GenericDefId::TypeAliasId(it) => it.lookup(db).container,