Merge #3656

3656: Simplify arenas r=matklad a=matklad

At the moment, Arena is paranetrized by two types: index and data. The original motivation was to allow index to be defined in the downstream crate, so that you can add inherent impls to the index. 

However, it seems like we've never actually used that capability, so perhaps we should switch to a generic Index impl? This PR tries this out, switching only `raw.rs` and parts of `hir_def`. 

wdyt?

Co-authored-by: Aleksey Kladov <aleksey.kladov@gmail.com>

Author: bors[bot]

crates/ra_arena/src/lib.rs

@@ -2,6 +2,7 @@
 
 use std::{
     fmt,
+    hash::{Hash, Hasher},
     iter::FromIterator,
     marker::PhantomData,
     ops::{Index, IndexMut},
@@ -36,86 +37,110 @@ impl fmt::Display for RawId {
     }
 }
 
-#[derive(Clone, PartialEq, Eq)]
-pub struct Arena<ID, T> {
-    data: Vec<T>,
-    _ty: PhantomData<ID>,
+pub struct Idx<T> {
+    raw: RawId,
+    _ty: PhantomData<fn() -> T>,
 }
 
-impl<ID: ArenaId, T: fmt::Debug> fmt::Debug for Arena<ID, T> {
-    fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
-        fmt.debug_struct("Arena").field("len", &self.len()).field("data", &self.data).finish()
+impl<T> Clone for Idx<T> {
+    fn clone(&self) -> Self {
+        *self
     }
 }
+impl<T> Copy for Idx<T> {}
 
-#[macro_export]
-macro_rules! impl_arena_id {
-    ($name:ident) => {
-        impl $crate::ArenaId for $name {
-            fn from_raw(raw: $crate::RawId) -> Self {
-                $name(raw)
-            }
-            fn into_raw(self) -> $crate::RawId {
-                self.0
-            }
+impl<T> PartialEq for Idx<T> {
+    fn eq(&self, other: &Idx<T>) -> bool {
+        self.raw == other.raw
+    }
+}
+impl<T> Eq for Idx<T> {}
+
+impl<T> Hash for Idx<T> {
+    fn hash<H: Hasher>(&self, state: &mut H) {
+        self.raw.hash(state)
+    }
+}
+
+impl<T> fmt::Debug for Idx<T> {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        let mut type_name = std::any::type_name::<T>();
+        if let Some(idx) = type_name.rfind(':') {
+            type_name = &type_name[idx + 1..]
         }
-    };
+        write!(f, "Idx::<{}>({})", type_name, self.raw)
+    }
 }
 
-pub trait ArenaId {
-    fn from_raw(raw: RawId) -> Self;
-    fn into_raw(self) -> RawId;
+impl<T> Idx<T> {
+    pub fn from_raw(raw: RawId) -> Self {
+        Idx { raw, _ty: PhantomData }
+    }
+    pub fn into_raw(self) -> RawId {
+        self.raw
+    }
+}
+
+#[derive(Clone, PartialEq, Eq)]
+pub struct Arena<T> {
+    data: Vec<T>,
 }
 
-impl<ID, T> Arena<ID, T> {
-    pub const fn new() -> Arena<ID, T> {
-        Arena { data: Vec::new(), _ty: PhantomData }
+impl<T: fmt::Debug> fmt::Debug for Arena<T> {
+    fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
+        fmt.debug_struct("Arena").field("len", &self.len()).field("data", &self.data).finish()
     }
 }
 
-impl<ID: ArenaId, T> Arena<ID, T> {
+impl<T> Arena<T> {
+    pub const fn new() -> Arena<T> {
+        Arena { data: Vec::new() }
+    }
+
     pub fn len(&self) -> usize {
         self.data.len()
     }
     pub fn is_empty(&self) -> bool {
         self.data.is_empty()
     }
-    pub fn alloc(&mut self, value: T) -> ID {
+    pub fn alloc(&mut self, value: T) -> Idx<T> {
         let id = RawId(self.data.len() as u32);
         self.data.push(value);
-        ID::from_raw(id)
+        Idx::from_raw(id)
     }
-    pub fn iter(&self) -> impl Iterator<Item = (ID, &T)> + ExactSizeIterator + DoubleEndedIterator {
-        self.data.iter().enumerate().map(|(idx, value)| (ID::from_raw(RawId(idx as u32)), value))
+    pub fn iter(
+        &self,
+    ) -> impl Iterator<Item = (Idx<T>, &T)> + ExactSizeIterator + DoubleEndedIterator {
+        self.data.iter().enumerate().map(|(idx, value)| (Idx::from_raw(RawId(idx as u32)), value))
     }
 }
 
-impl<ID: ArenaId, T> Default for Arena<ID, T> {
-    fn default() -> Arena<ID, T> {
-        Arena { data: Vec::new(), _ty: PhantomData }
+impl<T> Default for Arena<T> {
+    fn default() -> Arena<T> {
+        Arena { data: Vec::new() }
     }
 }
 
-impl<ID: ArenaId, T> Index<ID> for Arena<ID, T> {
+impl<T> Index<Idx<T>> for Arena<T> {
     type Output = T;
-    fn index(&self, idx: ID) -> &T {
+    fn index(&self, idx: Idx<T>) -> &T {
         let idx = idx.into_raw().0 as usize;
         &self.data[idx]
     }
 }
 
-impl<ID: ArenaId, T> IndexMut<ID> for Arena<ID, T> {
-    fn index_mut(&mut self, idx: ID) -> &mut T {
+impl<T> IndexMut<Idx<T>> for Arena<T> {
+    fn index_mut(&mut self, idx: Idx<T>) -> &mut T {
         let idx = idx.into_raw().0 as usize;
         &mut self.data[idx]
     }
 }
 
-impl<ID: ArenaId, T> FromIterator<T> for Arena<ID, T> {
+impl<T> FromIterator<T> for Arena<T> {
     fn from_iter<I>(iter: I) -> Self
     where
         I: IntoIterator<Item = T>,
     {
-        Arena { data: Vec::from_iter(iter), _ty: PhantomData }
+        Arena { data: Vec::from_iter(iter) }
     }
 }

crates/ra_arena/src/map.rs

@@ -2,17 +2,17 @@
 
 use std::marker::PhantomData;
 
-use super::ArenaId;
+use crate::Idx;
 
 /// A map from arena IDs to some other type. Space requirement is O(highest ID).
 #[derive(Debug, Clone, PartialEq, Eq, PartialOrd, Ord, Hash)]
-pub struct ArenaMap<ID, T> {
-    v: Vec<Option<T>>,
+pub struct ArenaMap<ID, V> {
+    v: Vec<Option<V>>,
     _ty: PhantomData<ID>,
 }
 
-impl<ID: ArenaId, T> ArenaMap<ID, T> {
-    pub fn insert(&mut self, id: ID, t: T) {
+impl<T, V> ArenaMap<Idx<T>, V> {
+    pub fn insert(&mut self, id: Idx<T>, t: V) {
         let idx = Self::to_idx(id);
         if self.v.capacity() <= idx {
             self.v.reserve(idx + 1 - self.v.capacity());
@@ -25,43 +25,43 @@ impl<ID: ArenaId, T> ArenaMap<ID, T> {
         self.v[idx] = Some(t);
     }
 
-    pub fn get(&self, id: ID) -> Option<&T> {
+    pub fn get(&self, id: Idx<T>) -> Option<&V> {
         self.v.get(Self::to_idx(id)).and_then(|it| it.as_ref())
     }
 
-    pub fn get_mut(&mut self, id: ID) -> Option<&mut T> {
+    pub fn get_mut(&mut self, id: Idx<T>) -> Option<&mut V> {
         self.v.get_mut(Self::to_idx(id)).and_then(|it| it.as_mut())
     }
 
-    pub fn values(&self) -> impl Iterator<Item = &T> {
+    pub fn values(&self) -> impl Iterator<Item = &V> {
         self.v.iter().filter_map(|o| o.as_ref())
     }
 
-    pub fn values_mut(&mut self) -> impl Iterator<Item = &mut T> {
+    pub fn values_mut(&mut self) -> impl Iterator<Item = &mut V> {
         self.v.iter_mut().filter_map(|o| o.as_mut())
     }
 
-    pub fn iter(&self) -> impl Iterator<Item = (ID, &T)> {
+    pub fn iter(&self) -> impl Iterator<Item = (Idx<T>, &V)> {
         self.v.iter().enumerate().filter_map(|(idx, o)| Some((Self::from_idx(idx), o.as_ref()?)))
     }
 
-    fn to_idx(id: ID) -> usize {
+    fn to_idx(id: Idx<T>) -> usize {
         u32::from(id.into_raw()) as usize
     }
 
-    fn from_idx(idx: usize) -> ID {
-        ID::from_raw((idx as u32).into())
+    fn from_idx(idx: usize) -> Idx<T> {
+        Idx::from_raw((idx as u32).into())
     }
 }
 
-impl<ID: ArenaId, T> std::ops::Index<ID> for ArenaMap<ID, T> {
+impl<T, V> std::ops::Index<Idx<V>> for ArenaMap<Idx<V>, T> {
     type Output = T;
-    fn index(&self, id: ID) -> &T {
+    fn index(&self, id: Idx<V>) -> &T {
         self.v[Self::to_idx(id)].as_ref().unwrap()
     }
 }
 
-impl<ID, T> Default for ArenaMap<ID, T> {
+impl<T, V> Default for ArenaMap<Idx<V>, T> {
     fn default() -> Self {
         ArenaMap { v: Vec::new(), _ty: PhantomData }
     }

crates/ra_hir_def/src/adt.rs

@@ -27,7 +27,7 @@ pub struct StructData {
 #[derive(Debug, Clone, PartialEq, Eq)]
 pub struct EnumData {
     pub name: Name,
-    pub variants: Arena<LocalEnumVariantId, EnumVariantData>,
+    pub variants: Arena<EnumVariantData>,
 }
 
 #[derive(Debug, Clone, PartialEq, Eq)]
@@ -38,8 +38,8 @@ pub struct EnumVariantData {
 
 #[derive(Debug, Clone, PartialEq, Eq)]
 pub enum VariantData {
-    Record(Arena<LocalStructFieldId, StructFieldData>),
-    Tuple(Arena<LocalStructFieldId, StructFieldData>),
+    Record(Arena<StructFieldData>),
+    Tuple(Arena<StructFieldData>),
     Unit,
 }
 
@@ -104,7 +104,7 @@ impl HasChildSource for EnumId {
 
 fn lower_enum(
     db: &dyn DefDatabase,
-    trace: &mut Trace<LocalEnumVariantId, EnumVariantData, ast::EnumVariant>,
+    trace: &mut Trace<EnumVariantData, ast::EnumVariant>,
     ast: &InFile<ast::EnumDef>,
 ) {
     for var in ast.value.variant_list().into_iter().flat_map(|it| it.variants()) {
@@ -128,8 +128,8 @@ impl VariantData {
         }
     }
 
-    pub fn fields(&self) -> &Arena<LocalStructFieldId, StructFieldData> {
-        const EMPTY: &Arena<LocalStructFieldId, StructFieldData> = &Arena::new();
+    pub fn fields(&self) -> &Arena<StructFieldData> {
+        const EMPTY: &Arena<StructFieldData> = &Arena::new();
         match &self {
             VariantData::Record(fields) | VariantData::Tuple(fields) => fields,
             _ => EMPTY,
@@ -183,11 +183,7 @@ pub enum StructKind {
 
 fn lower_struct(
     db: &dyn DefDatabase,
-    trace: &mut Trace<
-        LocalStructFieldId,
-        StructFieldData,
-        Either<ast::TupleFieldDef, ast::RecordFieldDef>,
-    >,
+    trace: &mut Trace<StructFieldData, Either<ast::TupleFieldDef, ast::RecordFieldDef>>,
     ast: &InFile<ast::StructKind>,
 ) -> StructKind {
     match &ast.value {

crates/ra_hir_def/src/body.rs

@@ -121,8 +121,8 @@ pub(crate) struct Mark {
 /// The body of an item (function, const etc.).
 #[derive(Debug, Eq, PartialEq)]
 pub struct Body {
-    pub exprs: Arena<ExprId, Expr>,
-    pub pats: Arena<PatId, Pat>,
+    pub exprs: Arena<Expr>,
+    pub pats: Arena<Pat>,
     /// The patterns for the function's parameters. While the parameter types are
     /// part of the function signature, the patterns are not (they don't change
     /// the external type of the function).

crates/ra_hir_def/src/body/lower.rs

@@ -24,8 +24,8 @@ use crate::{
     builtin_type::{BuiltinFloat, BuiltinInt},
     db::DefDatabase,
     expr::{
-        ArithOp, Array, BinaryOp, BindingAnnotation, CmpOp, Expr, ExprId, Literal, LogicOp,
-        MatchArm, Ordering, Pat, PatId, RecordFieldPat, RecordLitField, Statement,
+        dummy_expr_id, ArithOp, Array, BinaryOp, BindingAnnotation, CmpOp, Expr, ExprId, Literal,
+        LogicOp, MatchArm, Ordering, Pat, PatId, RecordFieldPat, RecordLitField, Statement,
     },
     item_scope::BuiltinShadowMode,
     path::GenericArgs,
@@ -51,7 +51,7 @@ pub(super) fn lower(
             exprs: Arena::default(),
             pats: Arena::default(),
             params: Vec::new(),
-            body_expr: ExprId::dummy(),
+            body_expr: dummy_expr_id(),
             item_scope: Default::default(),
         },
     }

crates/ra_hir_def/src/body/scope.rs

@@ -2,7 +2,7 @@
 use std::sync::Arc;
 
 use hir_expand::name::Name;
-use ra_arena::{impl_arena_id, Arena, RawId};
+use ra_arena::{Arena, Idx};
 use rustc_hash::FxHashMap;
 
 use crate::{
@@ -12,13 +12,11 @@ use crate::{
     DefWithBodyId,
 };
 
-#[derive(Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash)]
-pub struct ScopeId(RawId);
-impl_arena_id!(ScopeId);
+pub type ScopeId = Idx<ScopeData>;
 
 #[derive(Debug, PartialEq, Eq)]
 pub struct ExprScopes {
-    scopes: Arena<ScopeId, ScopeData>,
+    scopes: Arena<ScopeData>,
     scope_by_expr: FxHashMap<ExprId, ScopeId>,
 }
 

crates/ra_hir_def/src/expr.rs

@@ -13,7 +13,7 @@
 //! See also a neighboring `body` module.
 
 use hir_expand::name::Name;
-use ra_arena::{impl_arena_id, RawId};
+use ra_arena::{Idx, RawId};
 use ra_syntax::ast::RangeOp;
 
 use crate::{
@@ -22,19 +22,12 @@ use crate::{
     type_ref::{Mutability, TypeRef},
 };
 
-#[derive(Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash)]
-pub struct ExprId(RawId);
-impl_arena_id!(ExprId);
-
-impl ExprId {
-    pub fn dummy() -> ExprId {
-        ExprId((!0).into())
-    }
+pub type ExprId = Idx<Expr>;
+pub(crate) fn dummy_expr_id() -> ExprId {
+    ExprId::from_raw(RawId::from(!0))
 }
 
-#[derive(Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash)]
-pub struct PatId(RawId);
-impl_arena_id!(PatId);
+pub type PatId = Idx<Pat>;
 
 #[derive(Debug, Clone, Eq, PartialEq)]
 pub enum Literal {

crates/ra_hir_def/src/generics.rs

@@ -43,7 +43,7 @@ pub enum TypeParamProvenance {
 /// Data about the generic parameters of a function, struct, impl, etc.
 #[derive(Clone, PartialEq, Eq, Debug)]
 pub struct GenericParams {
-    pub types: Arena<LocalTypeParamId, TypeParamData>,
+    pub types: Arena<TypeParamData>,
     // lifetimes: Arena<LocalLifetimeParamId, LifetimeParamData>,
     pub where_predicates: Vec<WherePredicate>,
 }