5 files changed, 29 insertions, 26 deletions

diff --git a/crates/ra_arena/src/lib.rs b/crates/ra_arena/src/lib.rs
index 3ec8d3b60..984e1eec3 100644
--- a/crates/ra_arena/src/lib.rs
+++ b/crates/ra_arena/src/lib.rs
@@ -37,7 +37,7 @@ impl fmt::Display for RawId {
 }
 
 #[derive(Clone, PartialEq, Eq)]
-pub struct Arena<ID: ArenaId, T> {
+pub struct Arena<ID, T> {
     data: Vec<T>,
     _ty: PhantomData<ID>,
 }
@@ -67,6 +67,12 @@ pub trait ArenaId {
     fn into_raw(self) -> RawId;
 }
 
+impl<ID, T> Arena<ID, T> {
+    pub const fn new() -> Arena<ID, T> {
+        Arena { data: Vec::new(), _ty: PhantomData }
+    }
+}
+
 impl<ID: ArenaId, T> Arena<ID, T> {
     pub fn len(&self) -> usize {
         self.data.len()
diff --git a/crates/ra_hir/src/code_model.rs b/crates/ra_hir/src/code_model.rs
index 96a5cc857..ab0544a4c 100644
--- a/crates/ra_hir/src/code_model.rs
+++ b/crates/ra_hir/src/code_model.rs
@@ -301,7 +301,7 @@ pub enum FieldSource {
 
 impl StructField {
     pub fn name(&self, db: &impl HirDatabase) -> Name {
-        self.parent.variant_data(db).fields().unwrap()[self.id].name.clone()
+        self.parent.variant_data(db).fields()[self.id].name.clone()
     }
 
     pub fn ty(&self, db: &impl HirDatabase) -> Ty {
@@ -335,8 +335,7 @@ impl Struct {
         db.struct_data(self.id.into())
             .variant_data
             .fields()
-            .into_iter()
-            .flat_map(|it| it.iter())
+            .iter()
             .map(|(id, _)| StructField { parent: self.into(), id })
             .collect()
     }
@@ -345,8 +344,7 @@ impl Struct {
         db.struct_data(self.id.into())
             .variant_data
             .fields()
-            .into_iter()
-            .flat_map(|it| it.iter())
+            .iter()
             .find(|(_id, data)| data.name == *name)
             .map(|(id, _)| StructField { parent: self.into(), id })
     }
@@ -443,8 +441,7 @@ impl EnumVariant {
     pub fn fields(self, db: &impl HirDatabase) -> Vec<StructField> {
         self.variant_data(db)
             .fields()
-            .into_iter()
-            .flat_map(|it| it.iter())
+            .iter()
             .map(|(id, _)| StructField { parent: self.into(), id })
             .collect()
     }
@@ -452,8 +449,7 @@ impl EnumVariant {
     pub fn field(self, db: &impl HirDatabase, name: &Name) -> Option<StructField> {
         self.variant_data(db)
             .fields()
-            .into_iter()
-            .flat_map(|it| it.iter())
+            .iter()
             .find(|(_id, data)| data.name == *name)
             .map(|(id, _)| StructField { parent: self.into(), id })
     }
diff --git a/crates/ra_hir/src/from_source.rs b/crates/ra_hir/src/from_source.rs
index 72d059a27..1e7c22774 100644
--- a/crates/ra_hir/src/from_source.rs
+++ b/crates/ra_hir/src/from_source.rs
@@ -200,8 +200,7 @@ impl FromSource for StructField {
         variant_def
             .variant_data(db)
             .fields()
-            .into_iter()
-            .flat_map(|it| it.iter())
+            .iter()
             .map(|(id, _)| StructField { parent: variant_def, id })
             .find(|f| f.source(db) == src)
     }
diff --git a/crates/ra_hir/src/ty/lower.rs b/crates/ra_hir/src/ty/lower.rs
index 2272510e8..2b40cb07d 100644
--- a/crates/ra_hir/src/ty/lower.rs
+++ b/crates/ra_hir/src/ty/lower.rs
@@ -557,7 +557,7 @@ pub(crate) fn type_for_field(db: &impl HirDatabase, field: StructField) -> Ty {
         VariantDef::EnumVariant(it) => it.parent.id.resolver(db),
     };
     let var_data = parent_def.variant_data(db);
-    let type_ref = &var_data.fields().unwrap()[field.id].type_ref;
+    let type_ref = &var_data.fields()[field.id].type_ref;
     Ty::from_hir(db, &resolver, type_ref)
 }
 
@@ -696,10 +696,7 @@ impl From<Option<BuiltinFloat>> for Uncertain<FloatTy> {
 
 fn fn_sig_for_struct_constructor(db: &impl HirDatabase, def: Struct) -> FnSig {
     let struct_data = db.struct_data(def.id.into());
-    let fields = match struct_data.variant_data.fields() {
-        Some(fields) => fields,
-        None => panic!("fn_sig_for_struct_constructor called on unit struct"),
-    };
+    let fields = struct_data.variant_data.fields();
     let resolver = def.id.resolver(db);
     let params = fields
         .iter()
@@ -712,7 +709,7 @@ fn fn_sig_for_struct_constructor(db: &impl HirDatabase, def: Struct) -> FnSig {
 /// Build the type of a tuple struct constructor.
 fn type_for_struct_constructor(db: &impl HirDatabase, def: Struct) -> Ty {
     let struct_data = db.struct_data(def.id.into());
-    if struct_data.variant_data.fields().is_none() {
+    if struct_data.variant_data.is_unit() {
         return type_for_adt(db, def); // Unit struct
     }
     let generics = db.generic_params(def.id.into());
@@ -722,10 +719,7 @@ fn type_for_struct_constructor(db: &impl HirDatabase, def: Struct) -> Ty {
 
 fn fn_sig_for_enum_variant_constructor(db: &impl HirDatabase, def: EnumVariant) -> FnSig {
     let var_data = def.variant_data(db);
-    let fields = match var_data.fields() {
-        Some(fields) => fields,
-        None => panic!("fn_sig_for_enum_variant_constructor called for unit variant"),
-    };
+    let fields = var_data.fields();
     let resolver = def.parent.id.resolver(db);
     let params = fields
         .iter()
@@ -740,7 +734,7 @@ fn fn_sig_for_enum_variant_constructor(db: &impl HirDatabase, def: EnumVariant)
 /// Build the type of a tuple enum variant constructor.
 fn type_for_enum_variant_constructor(db: &impl HirDatabase, def: EnumVariant) -> Ty {
     let var_data = def.variant_data(db);
-    if var_data.fields().is_none() {
+    if var_data.is_unit() {
         return type_for_adt(db, def.parent_enum(db)); // Unit variant
     }
     let generics = db.generic_params(def.parent_enum(db).id.into());
diff --git a/crates/ra_hir_def/src/adt.rs b/crates/ra_hir_def/src/adt.rs
index a43f553aa..c9f30923e 100644
--- a/crates/ra_hir_def/src/adt.rs
+++ b/crates/ra_hir_def/src/adt.rs
@@ -109,10 +109,18 @@ impl VariantData {
         }
     }
 
-    pub fn fields(&self) -> Option<&Arena<LocalStructFieldId, StructFieldData>> {
+    pub fn fields(&self) -> &Arena<LocalStructFieldId, StructFieldData> {
+        const EMPTY: &Arena<LocalStructFieldId, StructFieldData> = &Arena::new();
         match &self {
-            VariantData::Record(fields) | VariantData::Tuple(fields) => Some(fields),
-            _ => None,
+            VariantData::Record(fields) | VariantData::Tuple(fields) => fields,
+            _ => EMPTY,
+        }
+    }
+
+    pub fn is_unit(&self) -> bool {
+        match self {
+            VariantData::Unit => true,
+            _ => false,
         }
     }
 }