3 files changed, 25 insertions, 14 deletions

diff --git a/crates/ra_hir/src/code_model.rs b/crates/ra_hir/src/code_model.rs
index 817c27410..63c85ca34 100644
--- a/crates/ra_hir/src/code_model.rs
+++ b/crates/ra_hir/src/code_model.rs
@@ -13,6 +13,7 @@ use hir_def::{
     AdtId, ConstId, DefWithBodyId, EnumId, FunctionId, HasModule, ImplId, LocalEnumVariantId,
     LocalModuleId, LocalStructFieldId, Lookup, ModuleId, StaticId, StructId, TraitId, TypeAliasId,
     TypeParamId, UnionId,
+    GenericDefId
 };
 use hir_expand::{
     diagnostics::DiagnosticSink,
@@ -21,7 +22,8 @@ use hir_expand::{
 };
 use hir_ty::{
     autoderef, display::HirFormatter, expr::ExprValidator, method_resolution, ApplicationTy,
-    Canonical, InEnvironment, TraitEnvironment, Ty, TyDefId, TypeCtor, TypeWalk,
+    Canonical, InEnvironment, TraitEnvironment, Ty, TyDefId, TypeCtor,
+    Substs
 };
 use ra_db::{CrateId, Edition, FileId};
 use ra_prof::profile;
@@ -270,7 +272,13 @@ impl StructField {
 
     pub fn ty(&self, db: &impl HirDatabase) -> Type {
         let var_id = self.parent.into();
-        let ty = db.field_types(var_id)[self.id].clone();
+        let generic_def_id: GenericDefId = match self.parent {
+            VariantDef::Struct(it) => it.id.into(),
+            VariantDef::Union(it) => it.id.into(),
+            VariantDef::EnumVariant(it) => it.parent.id.into(),
+        };
+        let substs = Substs::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.into(), var_id, ty)
     }
 
@@ -789,11 +797,7 @@ impl ImplBlock {
     pub fn target_ty(&self, db: &impl HirDatabase) -> Type {
         let impl_data = db.impl_data(self.id);
         let resolver = self.id.resolver(db);
-        let ctx = hir_ty::TyLoweringContext {
-            db,
-            resolver: &resolver,
-            impl_trait_mode: hir_ty::ImplTraitLoweringMode::Disallowed,
-        };
+        let ctx = hir_ty::TyLoweringContext::new(db, &resolver);
         let environment = TraitEnvironment::lower(db, &resolver);
         let ty = Ty::from_hir(&ctx, &impl_data.target_type);
         Type {
@@ -856,9 +860,10 @@ impl Type {
     fn from_def(
         db: &impl HirDatabase,
         krate: CrateId,
-        def: impl HasResolver + Into<TyDefId>,
+        def: impl HasResolver + Into<TyDefId> + Into<GenericDefId>,
     ) -> Type {
-        let ty = db.ty(def.into());
+        let substs = Substs::type_params(db, def);
+        let ty = db.ty(def.into()).subst(&substs);
         Type::new(db, krate, def, ty)
     }
 
@@ -955,7 +960,7 @@ impl Type {
             match a_ty.ctor {
                 TypeCtor::Tuple { .. } => {
                     for ty in a_ty.parameters.iter() {
-                        let ty = ty.clone().subst(&a_ty.parameters);
+                        let ty = ty.clone();
                         res.push(self.derived(ty));
                     }
                 }
diff --git a/crates/ra_hir_ty/src/lib.rs b/crates/ra_hir_ty/src/lib.rs
index a685e70c2..314be17b8 100644
--- a/crates/ra_hir_ty/src/lib.rs
+++ b/crates/ra_hir_ty/src/lib.rs
@@ -361,10 +361,16 @@ impl Substs {
     }
 
     /// Return Substs that replace each parameter by itself (i.e. `Ty::Param`).
-    pub(crate) fn type_params(generic_params: &Generics) -> Substs {
+    pub(crate) fn type_params_for_generics(generic_params: &Generics) -> Substs {
         Substs(generic_params.iter().map(|(id, _)| Ty::Param(id)).collect())
     }
 
+    /// 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());
+        Substs::type_params_for_generics(&params)
+    }
+
     /// Return Substs that replace each parameter by a bound variable.
     pub(crate) fn bound_vars(generic_params: &Generics) -> Substs {
         Substs(generic_params.iter().enumerate().map(|(idx, _)| Ty::Bound(idx as u32)).collect())
@@ -1026,7 +1032,7 @@ impl HirDisplay for Ty {
                     TypeParamProvenance::ArgumentImplTrait => {
                         write!(f, "impl ")?;
                         let bounds = f.db.generic_predicates_for_param(*id);
-                        let substs = Substs::type_params(&generics);
+                        let substs = Substs::type_params_for_generics(&generics);
                         write_bounds_like_dyn_trait(&bounds.iter().map(|b| b.clone().subst(&substs)).collect::<Vec<_>>(), f)?;
                     }
                 }
diff --git a/crates/ra_hir_ty/src/lower.rs b/crates/ra_hir_ty/src/lower.rs
index 847111748..0d4c075af 100644
--- a/crates/ra_hir_ty/src/lower.rs
+++ b/crates/ra_hir_ty/src/lower.rs
@@ -276,7 +276,7 @@ impl Ty {
             TypeNs::SelfType(impl_id) => {
                 let generics = generics(ctx.db, impl_id.into());
                 let substs = match ctx.type_param_mode {
-                    TypeParamLoweringMode::Placeholder => Substs::type_params(&generics),
+                    TypeParamLoweringMode::Placeholder => Substs::type_params_for_generics(&generics),
                     TypeParamLoweringMode::Variable => Substs::bound_vars(&generics),
                 };
                 ctx.db.impl_self_ty(impl_id).subst(&substs)
@@ -284,7 +284,7 @@ impl Ty {
             TypeNs::AdtSelfType(adt) => {
                 let generics = generics(ctx.db, adt.into());
                 let substs = match ctx.type_param_mode {
-                    TypeParamLoweringMode::Placeholder => Substs::type_params(&generics),
+                    TypeParamLoweringMode::Placeholder => Substs::type_params_for_generics(&generics),
                     TypeParamLoweringMode::Variable => Substs::bound_vars(&generics),
                 };
                 ctx.db.ty(adt.into()).subst(&substs)