4 files changed, 41 insertions, 22 deletions

diff --git a/crates/ra_hir/src/ty/infer/coerce.rs b/crates/ra_hir/src/ty/infer/coerce.rs
index 4ea038d99..54765da35 100644
--- a/crates/ra_hir/src/ty/infer/coerce.rs
+++ b/crates/ra_hir/src/ty/infer/coerce.rs
@@ -245,14 +245,17 @@ impl<'a, D: HirDatabase> InferenceContext<'a, D> {
                 ty_app!(TypeCtor::Adt(Adt::Struct(struct1)), st1),
                 ty_app!(TypeCtor::Adt(Adt::Struct(struct2)), st2),
             ) if struct1 == struct2 => {
-                let fields = struct1.fields(self.db);
-                let (last_field, prev_fields) = fields.split_last()?;
+                let field_tys = self.db.field_types(struct1.id.into());
+                let struct_data = self.db.struct_data(struct1.id.0);
+
+                let mut fields = struct_data.variant_data.fields().iter();
+                let (last_field_id, _data) = fields.next_back()?;
 
                 // Get the generic parameter involved in the last field.
                 let unsize_generic_index = {
                     let mut index = None;
                     let mut multiple_param = false;
-                    last_field.ty(self.db).walk(&mut |ty| match ty {
+                    field_tys[last_field_id].walk(&mut |ty| match ty {
                         &Ty::Param { idx, .. } => {
                             if index.is_none() {
                                 index = Some(idx);
@@ -271,8 +274,8 @@ impl<'a, D: HirDatabase> InferenceContext<'a, D> {
 
                 // Check other fields do not involve it.
                 let mut multiple_used = false;
-                prev_fields.iter().for_each(|field| {
-                    field.ty(self.db).walk(&mut |ty| match ty {
+                fields.for_each(|(field_id, _data)| {
+                    field_tys[field_id].walk(&mut |ty| match ty {
                         &Ty::Param { idx, .. } if idx == unsize_generic_index => {
                             multiple_used = true
                         }
diff --git a/crates/ra_hir/src/ty/infer/expr.rs b/crates/ra_hir/src/ty/infer/expr.rs
index 2996920c6..663ff9435 100644
--- a/crates/ra_hir/src/ty/infer/expr.rs
+++ b/crates/ra_hir/src/ty/infer/expr.rs
@@ -214,6 +214,8 @@ impl<'a, D: HirDatabase> InferenceContext<'a, D> {
                 self.unify(&ty, &expected.ty);
 
                 let substs = ty.substs().unwrap_or_else(Substs::empty);
+                let field_types =
+                    def_id.map(|it| self.db.field_types(it.into())).unwrap_or_default();
                 for (field_idx, field) in fields.iter().enumerate() {
                     let field_def = def_id.and_then(|it| match it.field(self.db, &field.name) {
                         Some(field) => Some(field),
@@ -228,8 +230,9 @@ impl<'a, D: HirDatabase> InferenceContext<'a, D> {
                     if let Some(field_def) = field_def {
                         self.result.record_field_resolutions.insert(field.expr, field_def);
                     }
-                    let field_ty =
-                        field_def.map_or(Ty::Unknown, |field| field.ty(self.db)).subst(&substs);
+                    let field_ty = field_def
+                        .map_or(Ty::Unknown, |it| field_types[it.id].clone())
+                        .subst(&substs);
                     self.infer_expr_coerce(field.expr, &Expectation::has_type(field_ty));
                 }
                 if let Some(expr) = spread {
@@ -252,7 +255,9 @@ impl<'a, D: HirDatabase> InferenceContext<'a, D> {
                             .and_then(|idx| a_ty.parameters.0.get(idx).cloned()),
                         TypeCtor::Adt(Adt::Struct(s)) => s.field(self.db, name).map(|field| {
                             self.write_field_resolution(tgt_expr, field);
-                            field.ty(self.db).subst(&a_ty.parameters)
+                            self.db.field_types(s.id.into())[field.id]
+                                .clone()
+                                .subst(&a_ty.parameters)
                         }),
                         _ => None,
                     },
diff --git a/crates/ra_hir/src/ty/infer/pat.rs b/crates/ra_hir/src/ty/infer/pat.rs
index c125ddfbc..641d61e87 100644
--- a/crates/ra_hir/src/ty/infer/pat.rs
+++ b/crates/ra_hir/src/ty/infer/pat.rs
@@ -27,10 +27,11 @@ impl<'a, D: HirDatabase> InferenceContext<'a, D> {
 
         let substs = ty.substs().unwrap_or_else(Substs::empty);
 
+        let field_tys = def.map(|it| self.db.field_types(it.into())).unwrap_or_default();
         for (i, &subpat) in subpats.iter().enumerate() {
             let expected_ty = def
                 .and_then(|d| d.field(self.db, &Name::new_tuple_field(i)))
-                .map_or(Ty::Unknown, |field| field.ty(self.db))
+                .map_or(Ty::Unknown, |field| field_tys[field.id].clone())
                 .subst(&substs);
             let expected_ty = self.normalize_associated_types_in(expected_ty);
             self.infer_pat(subpat, &expected_ty, default_bm);
@@ -56,10 +57,12 @@ impl<'a, D: HirDatabase> InferenceContext<'a, D> {
 
         let substs = ty.substs().unwrap_or_else(Substs::empty);
 
+        let field_tys = def.map(|it| self.db.field_types(it.into())).unwrap_or_default();
         for subpat in subpats {
             let matching_field = def.and_then(|it| it.field(self.db, &subpat.name));
-            let expected_ty =
-                matching_field.map_or(Ty::Unknown, |field| field.ty(self.db)).subst(&substs);
+            let expected_ty = matching_field
+                .map_or(Ty::Unknown, |field| field_tys[field.id].clone())
+                .subst(&substs);
             let expected_ty = self.normalize_associated_types_in(expected_ty);
             self.infer_pat(subpat.pat, &expected_ty, default_bm);
         }
diff --git a/crates/ra_hir/src/ty/lower.rs b/crates/ra_hir/src/ty/lower.rs
index 2b40cb07d..a39beb2a0 100644
--- a/crates/ra_hir/src/ty/lower.rs
+++ b/crates/ra_hir/src/ty/lower.rs
@@ -14,8 +14,9 @@ use hir_def::{
     path::{GenericArg, PathSegment},
     resolver::{HasResolver, Resolver, TypeNs},
     type_ref::{TypeBound, TypeRef},
-    AdtId, GenericDefId,
+    AdtId, GenericDefId, LocalStructFieldId, VariantId,
 };
+use ra_arena::map::ArenaMap;
 
 use super::{
     FnSig, GenericPredicate, ProjectionPredicate, ProjectionTy, Substs, TraitRef, Ty, TypeCtor,
@@ -29,7 +30,7 @@ use crate::{
     },
     util::make_mut_slice,
     Const, Enum, EnumVariant, Function, GenericDef, ImplBlock, ModuleDef, Path, Static, Struct,
-    StructField, Trait, TypeAlias, Union, VariantDef,
+    Trait, TypeAlias, Union,
 };
 
 // FIXME: this is only really used in `type_for_def`, which contains a bunch of
@@ -549,16 +550,23 @@ pub(crate) fn callable_item_sig(db: &impl HirDatabase, def: CallableDef) -> FnSi
     }
 }
 
-/// Build the type of a specific field of a struct or enum variant.
-pub(crate) fn type_for_field(db: &impl HirDatabase, field: StructField) -> Ty {
-    let parent_def = field.parent_def(db);
-    let resolver = match parent_def {
-        VariantDef::Struct(it) => it.id.resolver(db),
-        VariantDef::EnumVariant(it) => it.parent.id.resolver(db),
+/// Build the type of all specific fields of a struct or enum variant.
+pub(crate) fn field_types_query(
+    db: &impl HirDatabase,
+    variant_id: VariantId,
+) -> Arc<ArenaMap<LocalStructFieldId, Ty>> {
+    let (resolver, var_data) = match variant_id {
+        VariantId::StructId(it) => (it.resolver(db), db.struct_data(it.0).variant_data.clone()),
+        VariantId::EnumVariantId(it) => (
+            it.parent.resolver(db),
+            db.enum_data(it.parent).variants[it.local_id].variant_data.clone(),
+        ),
     };
-    let var_data = parent_def.variant_data(db);
-    let type_ref = &var_data.fields()[field.id].type_ref;
-    Ty::from_hir(db, &resolver, type_ref)
+    let mut res = ArenaMap::default();
+    for (field_id, field_data) in var_data.fields().iter() {
+        res.insert(field_id, Ty::from_hir(db, &resolver, &field_data.type_ref))
+    }
+    Arc::new(res)
 }
 
 /// This query exists only to be used when resolving short-hand associated types