5 files changed, 48 insertions, 22 deletions

diff --git a/crates/hir/src/attrs.rs b/crates/hir/src/attrs.rs
index 505fc05e7..dab8da7bb 100644
--- a/crates/hir/src/attrs.rs
+++ b/crates/hir/src/attrs.rs
@@ -125,5 +125,5 @@ fn resolve_doc_path(
         Some(Namespace::Macros) => return None,
         None => resolved.iter_items().find_map(|it| it.as_module_def_id())?,
     };
-    Some(def.into())
+    Some(def)
 }
diff --git a/crates/hir/src/display.rs b/crates/hir/src/display.rs
index 44cdcc296..9f6d7be48 100644
--- a/crates/hir/src/display.rs
+++ b/crates/hir/src/display.rs
@@ -12,8 +12,8 @@ use hir_ty::display::{
 use syntax::ast::{self, NameOwner};
 
 use crate::{
-    Const, ConstParam, Enum, Field, Function, HasVisibility, Module, Static, Struct, Substs, Trait,
-    Type, TypeAlias, TypeParam, Union, Variant,
+    Adt, Const, ConstParam, Enum, Field, Function, GenericParam, HasVisibility, LifetimeParam,
+    Module, Static, Struct, Substitution, Trait, Type, TypeAlias, TypeParam, Union, Variant,
 };
 
 impl HirDisplay for Function {
@@ -120,6 +120,16 @@ impl HirDisplay for Function {
     }
 }
 
+impl HirDisplay for Adt {
+    fn hir_fmt(&self, f: &mut HirFormatter) -> Result<(), HirDisplayError> {
+        match self {
+            Adt::Struct(it) => it.hir_fmt(f),
+            Adt::Union(it) => it.hir_fmt(f),
+            Adt::Enum(it) => it.hir_fmt(f),
+        }
+    }
+}
+
 impl HirDisplay for Struct {
     fn hir_fmt(&self, f: &mut HirFormatter) -> Result<(), HirDisplayError> {
         write_visibility(self.module(f.db).id, self.visibility(f.db), f)?;
@@ -211,11 +221,21 @@ impl HirDisplay for Type {
     }
 }
 
+impl HirDisplay for GenericParam {
+    fn hir_fmt(&self, f: &mut HirFormatter) -> Result<(), HirDisplayError> {
+        match self {
+            GenericParam::TypeParam(it) => it.hir_fmt(f),
+            GenericParam::LifetimeParam(it) => it.hir_fmt(f),
+            GenericParam::ConstParam(it) => it.hir_fmt(f),
+        }
+    }
+}
+
 impl HirDisplay for TypeParam {
     fn hir_fmt(&self, f: &mut HirFormatter) -> Result<(), HirDisplayError> {
         write!(f, "{}", self.name(f.db))?;
         let bounds = f.db.generic_predicates_for_param(self.id);
-        let substs = Substs::type_params(f.db, self.id.parent);
+        let substs = Substitution::type_params(f.db, self.id.parent);
         let predicates = bounds.iter().cloned().map(|b| b.subst(&substs)).collect::<Vec<_>>();
         if !(predicates.is_empty() || f.omit_verbose_types()) {
             write_bounds_like_dyn_trait_with_prefix(":", &predicates, f)?;
@@ -224,6 +244,12 @@ impl HirDisplay for TypeParam {
     }
 }
 
+impl HirDisplay for LifetimeParam {
+    fn hir_fmt(&self, f: &mut HirFormatter) -> Result<(), HirDisplayError> {
+        write!(f, "{}", self.name(f.db))
+    }
+}
+
 impl HirDisplay for ConstParam {
     fn hir_fmt(&self, f: &mut HirFormatter) -> Result<(), HirDisplayError> {
         write!(f, "const {}: ", self.name(f.db))?;
diff --git a/crates/hir/src/lib.rs b/crates/hir/src/lib.rs
index 265a084f3..b41a36a78 100644
--- a/crates/hir/src/lib.rs
+++ b/crates/hir/src/lib.rs
@@ -57,8 +57,8 @@ use hir_ty::{
     to_assoc_type_id,
     traits::{FnTrait, Solution, SolutionVariables},
     AliasTy, BoundVar, CallableDefId, CallableSig, Canonical, DebruijnIndex, GenericPredicate,
-    InEnvironment, Interner, Obligation, ProjectionPredicate, ProjectionTy, Scalar, Substs, Ty,
-    TyDefId, TyKind, TyVariableKind,
+    InEnvironment, Interner, Obligation, ProjectionPredicate, ProjectionTy, Scalar, Substitution,
+    Ty, TyDefId, TyKind, TyVariableKind,
 };
 use itertools::Itertools;
 use rustc_hash::FxHashSet;
@@ -518,7 +518,7 @@ impl Field {
             VariantDef::Union(it) => it.id.into(),
             VariantDef::Variant(it) => it.parent.id.into(),
         };
-        let substs = Substs::type_params(db, generic_def_id);
+        let substs = Substitution::type_params(db, generic_def_id);
         let ty = db.field_types(var_id)[self.id].clone().subst(&substs);
         Type::new(db, self.parent.module(db).id.krate(), var_id, ty)
     }
@@ -1335,7 +1335,7 @@ impl Local {
 
     // FIXME: why is this an option? It shouldn't be?
     pub fn name(self, db: &dyn HirDatabase) -> Option<Name> {
-        let body = db.body(self.parent.into());
+        let body = db.body(self.parent);
         match &body[self.pat_id] {
             Pat::Bind { name, .. } => Some(name.clone()),
             _ => None,
@@ -1347,7 +1347,7 @@ impl Local {
     }
 
     pub fn is_mut(self, db: &dyn HirDatabase) -> bool {
-        let body = db.body(self.parent.into());
+        let body = db.body(self.parent);
         matches!(&body[self.pat_id], Pat::Bind { mode: BindingAnnotation::Mutable, .. })
     }
 
@@ -1360,7 +1360,7 @@ impl Local {
     }
 
     pub fn ty(self, db: &dyn HirDatabase) -> Type {
-        let def = DefWithBodyId::from(self.parent);
+        let def = self.parent;
         let infer = db.infer(def);
         let ty = infer[self.pat_id].clone();
         let krate = def.module(db.upcast()).krate();
@@ -1368,7 +1368,7 @@ impl Local {
     }
 
     pub fn source(self, db: &dyn HirDatabase) -> InFile<Either<ast::IdentPat, ast::SelfParam>> {
-        let (_body, source_map) = db.body_with_source_map(self.parent.into());
+        let (_body, source_map) = db.body_with_source_map(self.parent);
         let src = source_map.pat_syntax(self.pat_id).unwrap(); // Hmm...
         let root = src.file_syntax(db.upcast());
         src.map(|ast| {
@@ -1393,12 +1393,12 @@ impl Label {
     }
 
     pub fn name(self, db: &dyn HirDatabase) -> Name {
-        let body = db.body(self.parent.into());
+        let body = db.body(self.parent);
         body[self.label_id].name.clone()
     }
 
     pub fn source(self, db: &dyn HirDatabase) -> InFile<ast::Label> {
-        let (_body, source_map) = db.body_with_source_map(self.parent.into());
+        let (_body, source_map) = db.body_with_source_map(self.parent);
         let src = source_map.label_syntax(self.label_id);
         let root = src.file_syntax(db.upcast());
         src.map(|ast| ast.to_node(&root))
@@ -1471,7 +1471,7 @@ impl TypeParam {
         let resolver = self.id.parent.resolver(db.upcast());
         let krate = self.id.parent.module(db.upcast()).krate();
         let ty = params.get(local_idx)?.clone();
-        let subst = Substs::type_params(db, self.id.parent);
+        let subst = Substitution::type_params(db, self.id.parent);
         let ty = ty.subst(&subst.prefix(local_idx));
         Some(Type::new_with_resolver_inner(db, krate, &resolver, ty))
     }
@@ -1674,7 +1674,7 @@ impl Type {
         krate: CrateId,
         def: impl HasResolver + Into<TyDefId> + Into<GenericDefId>,
     ) -> Type {
-        let substs = Substs::build_for_def(db, def).fill_with_unknown().build();
+        let substs = Substitution::build_for_def(db, def).fill_with_unknown().build();
         let ty = db.ty(def.into()).subst(&substs);
         Type::new(db, krate, def, ty)
     }
@@ -1754,7 +1754,7 @@ impl Type {
     pub fn impls_trait(&self, db: &dyn HirDatabase, trait_: Trait, args: &[Type]) -> bool {
         let trait_ref = hir_ty::TraitRef {
             trait_: trait_.id,
-            substs: Substs::build_for_def(db, trait_.id)
+            substs: Substitution::build_for_def(db, trait_.id)
                 .push(self.ty.value.clone())
                 .fill(args.iter().map(|t| t.ty.value.clone()))
                 .build(),
@@ -1778,7 +1778,7 @@ impl Type {
         args: &[Type],
         alias: TypeAlias,
     ) -> Option<Type> {
-        let subst = Substs::build_for_def(db, trait_.id)
+        let subst = Substitution::build_for_def(db, trait_.id)
             .push(self.ty.value.clone())
             .fill(args.iter().map(|t| t.ty.value.clone()))
             .build();
@@ -2045,7 +2045,7 @@ impl Type {
         fn walk_substs(
             db: &dyn HirDatabase,
             type_: &Type,
-            substs: &Substs,
+            substs: &Substitution,
             cb: &mut impl FnMut(Type),
         ) {
             for ty in substs.iter() {
diff --git a/crates/hir/src/semantics.rs b/crates/hir/src/semantics.rs
index c7e0d0be3..e0eb2a66d 100644
--- a/crates/hir/src/semantics.rs
+++ b/crates/hir/src/semantics.rs
@@ -836,7 +836,7 @@ impl<'a> SemanticsScope<'a> {
                 resolver::ScopeDef::AdtSelfType(it) => ScopeDef::AdtSelfType(it.into()),
                 resolver::ScopeDef::GenericParam(id) => ScopeDef::GenericParam(id.into()),
                 resolver::ScopeDef::Local(pat_id) => {
-                    let parent = resolver.body_owner().unwrap().into();
+                    let parent = resolver.body_owner().unwrap();
                     ScopeDef::Local(Local { parent, pat_id })
                 }
             };
diff --git a/crates/hir/src/source_analyzer.rs b/crates/hir/src/source_analyzer.rs
index 4d59293e9..37d162b32 100644
--- a/crates/hir/src/source_analyzer.rs
+++ b/crates/hir/src/source_analyzer.rs
@@ -20,7 +20,7 @@ use hir_def::{
 use hir_expand::{hygiene::Hygiene, name::AsName, HirFileId, InFile};
 use hir_ty::{
     diagnostics::{record_literal_missing_fields, record_pattern_missing_fields},
-    InferenceResult, Substs,
+    InferenceResult, Substitution,
 };
 use syntax::{
     ast::{self, AstNode},
@@ -329,7 +329,7 @@ impl SourceAnalyzer {
         &self,
         db: &dyn HirDatabase,
         krate: CrateId,
-        substs: &Substs,
+        substs: &Substitution,
         variant: VariantId,
         missing_fields: Vec<LocalFieldId>,
     ) -> Vec<(Field, Type)> {
@@ -484,7 +484,7 @@ fn resolve_hir_path_(
         resolver.resolve_path_in_value_ns_fully(db.upcast(), path.mod_path()).and_then(|val| {
             let res = match val {
                 ValueNs::LocalBinding(pat_id) => {
-                    let var = Local { parent: body_owner?.into(), pat_id };
+                    let var = Local { parent: body_owner?, pat_id };
                     PathResolution::Local(var)
                 }
                 ValueNs::FunctionId(it) => PathResolution::Def(Function::from(it).into()),