15 files changed, 167 insertions, 187 deletions

diff --git a/Cargo.lock b/Cargo.lock
index 5f35f2872..b06058688 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -371,11 +371,6 @@ version = "1.1.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 
 [[package]]
-name = "id-arena"
-version = "2.0.0"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-
-[[package]]
 name = "idna"
 version = "0.1.5"
 source = "registry+https://github.com/rust-lang/crates.io-index"
@@ -684,6 +679,10 @@ dependencies = [
 ]
 
 [[package]]
+name = "ra_arena"
+version = "0.1.0"
+
+[[package]]
 name = "ra_cli"
 version = "0.1.0"
 dependencies = [
@@ -729,9 +728,9 @@ dependencies = [
  "arrayvec 0.4.10 (registry+https://github.com/rust-lang/crates.io-index)",
  "ena 0.11.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "flexi_logger 0.10.3 (registry+https://github.com/rust-lang/crates.io-index)",
- "id-arena 2.0.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "log 0.4.6 (registry+https://github.com/rust-lang/crates.io-index)",
  "parking_lot 0.7.0 (registry+https://github.com/rust-lang/crates.io-index)",
+ "ra_arena 0.1.0",
  "ra_db 0.1.0",
  "ra_editor 0.1.0",
  "ra_syntax 0.1.0",
@@ -808,6 +807,7 @@ version = "0.1.0"
 dependencies = [
  "crossbeam-channel 0.3.6 (registry+https://github.com/rust-lang/crates.io-index)",
  "log 0.4.6 (registry+https://github.com/rust-lang/crates.io-index)",
+ "ra_arena 0.1.0",
  "relative-path 0.4.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "rustc-hash 1.0.1 (registry+https://github.com/rust-lang/crates.io-index)",
  "tempfile 3.0.5 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -1529,7 +1529,6 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 "checksum glob 0.2.11 (registry+https://github.com/rust-lang/crates.io-index)" = "8be18de09a56b60ed0edf84bc9df007e30040691af7acd1c41874faac5895bfb"
 "checksum heck 0.3.1 (registry+https://github.com/rust-lang/crates.io-index)" = "20564e78d53d2bb135c343b3f47714a56af2061f1c928fdb541dc7b9fdd94205"
 "checksum humansize 1.1.0 (registry+https://github.com/rust-lang/crates.io-index)" = "b6cab2627acfc432780848602f3f558f7e9dd427352224b0d9324025796d2a5e"
-"checksum id-arena 2.0.0 (registry+https://github.com/rust-lang/crates.io-index)" = "3a7250033feafee46a1cecd2c2616a64aec1d064f38c9ae2bdd297728542843e"
 "checksum idna 0.1.5 (registry+https://github.com/rust-lang/crates.io-index)" = "38f09e0f0b1fb55fdee1f17470ad800da77af5186a1a76c026b679358b7e844e"
 "checksum im 12.2.0 (registry+https://github.com/rust-lang/crates.io-index)" = "ae9c7f9bb8aee47fc16d535a705f7867a9fc83bb822e5e1043bb98e77ffeed3c"
 "checksum indexmap 1.0.2 (registry+https://github.com/rust-lang/crates.io-index)" = "7e81a7c05f79578dbc15793d8b619db9ba32b4577003ef3af1a91c416798c58d"
diff --git a/crates/ra_arena/Cargo.toml b/crates/ra_arena/Cargo.toml
new file mode 100644
index 000000000..9594e2d0f
--- /dev/null
+++ b/crates/ra_arena/Cargo.toml
@@ -0,0 +1,5 @@
+[package]
+edition = "2018"
+name = "ra_arena"
+version = "0.1.0"
+authors = ["Aleksey Kladov <[email protected]>"]
diff --git a/crates/ra_arena/src/lib.rs b/crates/ra_arena/src/lib.rs
new file mode 100644
index 000000000..a5eeb4118
--- /dev/null
+++ b/crates/ra_arena/src/lib.rs
@@ -0,0 +1,97 @@
+//! Yet another index-based arena.
+
+use std::{
+    fmt,
+    marker::PhantomData,
+    ops::{Index, IndexMut},
+};
+
+#[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash)]
+pub struct RawId(u32);
+
+impl From<RawId> for u32 {
+    fn from(raw: RawId) -> u32 {
+        raw.0
+    }
+}
+
+impl From<u32> for RawId {
+    fn from(id: u32) -> RawId {
+        RawId(id)
+    }
+}
+
+impl fmt::Debug for RawId {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        self.0.fmt(f)
+    }
+}
+
+impl fmt::Display for RawId {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        self.0.fmt(f)
+    }
+}
+
+#[derive(Clone, Debug, PartialEq, Eq)]
+pub struct Arena<ID: ArenaId, T> {
+    data: Vec<T>,
+    _ty: PhantomData<ID>,
+}
+
+#[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
+            }
+        }
+    };
+}
+
+pub trait ArenaId {
+    fn from_raw(raw: RawId) -> Self;
+    fn into_raw(self) -> RawId;
+}
+
+impl<ID: ArenaId, T> Arena<ID, T> {
+    pub fn alloc(&mut self, value: T) -> ID {
+        let id = RawId(self.data.len() as u32);
+        self.data.push(value);
+        ID::from_raw(id)
+    }
+    pub fn iter<'a>(&'a self) -> impl Iterator<Item = (ID, &'a T)> {
+        self.data
+            .iter()
+            .enumerate()
+            .map(|(idx, value)| (ID::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<ID: ArenaId, T> Index<ID> for Arena<ID, T> {
+    type Output = T;
+    fn index(&self, idx: ID) -> &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 {
+        let idx = idx.into_raw().0 as usize;
+        &mut self.data[idx]
+    }
+}
diff --git a/crates/ra_hir/Cargo.toml b/crates/ra_hir/Cargo.toml
index c3fbd327d..8c0cf4b86 100644
--- a/crates/ra_hir/Cargo.toml
+++ b/crates/ra_hir/Cargo.toml
@@ -11,9 +11,9 @@ relative-path = "0.4.0"
 salsa = "0.9.0"
 rustc-hash = "1.0"
 parking_lot = "0.7.0"
-id-arena = "2.0"
 ena = "0.11"
 ra_syntax = { path = "../ra_syntax" }
+ra_arena = { path = "../ra_arena" }
 ra_editor = { path = "../ra_editor" }
 ra_db = { path = "../ra_db" }
 test_utils = { path = "../test_utils" }
diff --git a/crates/ra_hir/src/arena.rs b/crates/ra_hir/src/arena.rs
deleted file mode 100644
index d4f9d9cb9..000000000
--- a/crates/ra_hir/src/arena.rs
+++ /dev/null
@@ -1,66 +0,0 @@
-//! A simple id-based arena, similar to https://github.com/fitzgen/id-arena.
-//! We use our own version for more compact id's and to allow inherent impls
-//! on Ids.
-
-use std::{
-    fmt,
-    hash::{Hash, Hasher},
-    marker::PhantomData,
-};
-
-pub struct Id<T> {
-    idx: u32,
-    _ty: PhantomData<fn() -> T>,
-}
-
-impl<T> fmt::Debug for Id<T> {
-    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
-        f.debug_tuple("Id").field(&self.idx).finish()
-    }
-}
-impl<T> Copy for Id<T> {}
-impl<T> Clone for Id<T> {
-    fn clone(&self) -> Id<T> {
-        *self
-    }
-}
-
-impl<T> PartialEq for Id<T> {
-    fn eq(&self, other: &Id<T>) -> bool {
-        self.idx == other.idx
-    }
-}
-
-impl<T> Eq for Id<T> {}
-
-impl<T> Hash for Id<T> {
-    fn hash<H: Hasher>(&self, h: &mut H) {
-        self.idx.hash(h);
-    }
-}
-
-#[derive(Debug, PartialEq, Eq)]
-pub(crate) struct ArenaBehavior<T> {
-    _ty: PhantomData<T>,
-}
-
-impl<T> id_arena::ArenaBehavior for ArenaBehavior<T> {
-    type Id = Id<T>;
-    fn new_arena_id() -> u32 {
-        0
-    }
-    fn new_id(_arena_id: u32, index: usize) -> Id<T> {
-        Id {
-            idx: index as u32,
-            _ty: PhantomData,
-        }
-    }
-    fn index(id: Id<T>) -> usize {
-        id.idx as usize
-    }
-    fn arena_id(_id: Id<T>) -> u32 {
-        0
-    }
-}
-
-pub(crate) type Arena<T> = id_arena::Arena<T, ArenaBehavior<T>>;
diff --git a/crates/ra_hir/src/function/scope.rs b/crates/ra_hir/src/function/scope.rs
index 3e4cfad0c..42bfe4f32 100644
--- a/crates/ra_hir/src/function/scope.rs
+++ b/crates/ra_hir/src/function/scope.rs
@@ -5,19 +5,19 @@ use ra_syntax::{
     algo::generate,
     ast::{self, ArgListOwner, LoopBodyOwner, NameOwner},
 };
+use ra_arena::{Arena, RawId, impl_arena_id};
 use ra_db::LocalSyntaxPtr;
 
-use crate::{
-    arena::{Arena, Id},
-    Name, AsName,
-};
+use crate::{Name, AsName};
 
-pub(crate) type ScopeId = Id<ScopeData>;
+#[derive(Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash)]
+pub struct ScopeId(RawId);
+impl_arena_id!(ScopeId);
 
 #[derive(Debug, PartialEq, Eq)]
 pub struct FnScopes {
     pub self_param: Option<LocalSyntaxPtr>,
-    scopes: Arena<ScopeData>,
+    scopes: Arena<ScopeId, ScopeData>,
     scope_for: FxHashMap<LocalSyntaxPtr, ScopeId>,
 }
 
diff --git a/crates/ra_hir/src/ids.rs b/crates/ra_hir/src/ids.rs
index 4c7ebe3ea..66adacc7d 100644
--- a/crates/ra_hir/src/ids.rs
+++ b/crates/ra_hir/src/ids.rs
@@ -1,10 +1,8 @@
 use ra_db::{SourceRootId, LocationIntener, Cancelable, FileId};
 use ra_syntax::{SourceFileNode, SyntaxKind, SyntaxNode, SyntaxNodeRef, SourceFile, AstNode, ast};
+use ra_arena::{Arena, RawId, impl_arena_id};
 
-use crate::{
-    HirDatabase, PerNs, ModuleId, Module, Def, Function, Struct, Enum,
-    arena::{Arena, Id},
-};
+use crate::{HirDatabase, PerNs, ModuleId, Module, Def, Function, Struct, Enum};
 
 /// hir makes a heavy use of ids: integer (u32) handlers to various things. You
 /// can think of id as a pointer (but without a lifetime) or a file descriptor
@@ -206,7 +204,9 @@ impl DefKind {
 
 /// Identifier of item within a specific file. This is stable over reparses, so
 /// it's OK to use it as a salsa key/value.
-pub(crate) type SourceFileItemId = Id<SyntaxNode>;
+#[derive(Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash)]
+pub struct SourceFileItemId(RawId);
+impl_arena_id!(SourceFileItemId);
 
 #[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
 pub struct SourceItemId {
@@ -219,7 +219,7 @@ pub struct SourceItemId {
 #[derive(Debug, PartialEq, Eq)]
 pub struct SourceFileItems {
     file_id: HirFileId,
-    arena: Arena<SyntaxNode>,
+    arena: Arena<SourceFileItemId, SyntaxNode>,
 }
 
 impl SourceFileItems {
diff --git a/crates/ra_hir/src/lib.rs b/crates/ra_hir/src/lib.rs
index 8ee52a466..344b543b6 100644
--- a/crates/ra_hir/src/lib.rs
+++ b/crates/ra_hir/src/lib.rs
@@ -19,7 +19,6 @@ pub mod db;
 mod mock;
 mod query_definitions;
 mod path;
-mod arena;
 pub mod source_binder;
 
 mod ids;
diff --git a/crates/ra_hir/src/module.rs b/crates/ra_hir/src/module.rs
index a53b69d20..c70dc54dd 100644
--- a/crates/ra_hir/src/module.rs
+++ b/crates/ra_hir/src/module.rs
@@ -9,6 +9,7 @@ use ra_syntax::{
     ast::{self, AstNode, NameOwner},
     SyntaxNode,
 };
+use ra_arena::{Arena, RawId, impl_arena_id};
 use ra_db::{SourceRootId, FileId, Cancelable};
 use relative_path::RelativePathBuf;
 
@@ -16,7 +17,6 @@ use crate::{
     Def, DefKind, DefLoc, DefId,
     Name, Path, PathKind, HirDatabase, SourceItemId, SourceFileItemId, Crate,
     HirFileId,
-    arena::{Arena, Id},
 };
 
 pub use self::nameres::{ModuleScope, Resolution, Namespace, PerNs};
@@ -173,6 +173,14 @@ impl Module {
     }
 }
 
+#[derive(Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash)]
+pub struct ModuleId(RawId);
+impl_arena_id!(ModuleId);
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash)]
+pub struct LinkId(RawId);
+impl_arena_id!(LinkId);
+
 /// Physically, rust source is organized as a set of files, but logically it is
 /// organized as a tree of modules. Usually, a single file corresponds to a
 /// single module, but it is not nessary the case.
@@ -182,8 +190,8 @@ impl Module {
 /// always have one parent).
 #[derive(Default, Debug, PartialEq, Eq)]
 pub struct ModuleTree {
-    mods: Arena<ModuleData>,
-    links: Arena<LinkData>,
+    mods: Arena<ModuleId, ModuleData>,
+    links: Arena<LinkId, LinkData>,
 }
 
 impl ModuleTree {
@@ -210,9 +218,6 @@ pub(crate) enum ModuleSourceNode {
     Module(ast::ModuleNode),
 }
 
-pub type ModuleId = Id<ModuleData>;
-type LinkId = Id<LinkData>;
-
 #[derive(Clone, Debug, Hash, PartialEq, Eq)]
 pub enum Problem {
     UnresolvedModule {
diff --git a/crates/ra_lsp_server/src/main_loop.rs b/crates/ra_lsp_server/src/main_loop.rs
index 06dd373c0..60d9671de 100644
--- a/crates/ra_lsp_server/src/main_loop.rs
+++ b/crates/ra_lsp_server/src/main_loop.rs
@@ -350,7 +350,7 @@ fn on_notification(
                 .write()
                 .add_file_overlay(&path, params.text_document.text)
             {
-                subs.add_sub(FileId(file_id.0));
+                subs.add_sub(FileId(file_id.0.into()));
             }
             return Ok(());
         }
@@ -379,7 +379,7 @@ fn on_notification(
                 .to_file_path()
                 .map_err(|()| format_err!("invalid uri: {}", uri))?;
             if let Some(file_id) = state.vfs.write().remove_file_overlay(path.as_path()) {
-                subs.remove_sub(FileId(file_id.0));
+                subs.remove_sub(FileId(file_id.0.into()));
             }
             let params = req::PublishDiagnosticsParams {
                 uri,
diff --git a/crates/ra_lsp_server/src/main_loop/handlers.rs b/crates/ra_lsp_server/src/main_loop/handlers.rs
index b5792f3b8..4e895a9a9 100644
--- a/crates/ra_lsp_server/src/main_loop/handlers.rs
+++ b/crates/ra_lsp_server/src/main_loop/handlers.rs
@@ -337,7 +337,10 @@ pub fn handle_runnables(
                 None => return Ok(None),
             };
             let file_id = world.analysis().crate_root(crate_id)?;
-            let path = world.vfs.read().file2path(ra_vfs::VfsFile(file_id.0));
+            let path = world
+                .vfs
+                .read()
+                .file2path(ra_vfs::VfsFile(file_id.0.into()));
             let res = world.workspaces.iter().find_map(|ws| {
                 let tgt = ws.target_by_root(&path)?;
                 let res = CargoTargetSpec {
diff --git a/crates/ra_lsp_server/src/server_world.rs b/crates/ra_lsp_server/src/server_world.rs
index c183c25af..ebf2b15cc 100644
--- a/crates/ra_lsp_server/src/server_world.rs
+++ b/crates/ra_lsp_server/src/server_world.rs
@@ -49,7 +49,7 @@ impl ServerWorldState {
         let (mut vfs, roots) = Vfs::new(roots);
         for r in roots {
             let is_local = vfs.root2path(r).starts_with(&root);
-            change.add_root(SourceRootId(r.0), is_local);
+            change.add_root(SourceRootId(r.0.into()), is_local);
         }
 
         let mut crate_graph = CrateGraph::default();
@@ -60,7 +60,7 @@ impl ServerWorldState {
                 for tgt in pkg.targets(ws) {
                     let root = tgt.root(ws);
                     if let Some(file_id) = vfs.load(root) {
-                        let file_id = FileId(file_id.0);
+                        let file_id = FileId(file_id.0.into());
                         let crate_id = crate_graph.add_crate_root(file_id);
                         if tgt.kind(ws) == TargetKind::Lib {
                             pkg_to_lib_crate.insert(pkg, crate_id);
@@ -113,14 +113,19 @@ impl ServerWorldState {
                     if root_path.starts_with(&self.root) {
                         self.roots_to_scan -= 1;
                         for (file, path, text) in files {
-                            change.add_file(SourceRootId(root.0), FileId(file.0), path, text);
+                            change.add_file(
+                                SourceRootId(root.0.into()),
+                                FileId(file.0.into()),
+                                path,
+                                text,
+                            );
                         }
                     } else {
                         let files = files
                             .into_iter()
-                            .map(|(vfsfile, path, text)| (FileId(vfsfile.0), path, text))
+                            .map(|(vfsfile, path, text)| (FileId(vfsfile.0.into()), path, text))
                             .collect();
-                        libs.push((SourceRootId(root.0), files));
+                        libs.push((SourceRootId(root.0.into()), files));
                     }
                 }
                 VfsChange::AddFile {
@@ -129,13 +134,18 @@ impl ServerWorldState {
                     path,
                     text,
                 } => {
-                    change.add_file(SourceRootId(root.0), FileId(file.0), path, text);
+                    change.add_file(
+                        SourceRootId(root.0.into()),
+                        FileId(file.0.into()),
+                        path,
+                        text,
+                    );
                 }
                 VfsChange::RemoveFile { root, file, path } => {
-                    change.remove_file(SourceRootId(root.0), FileId(file.0), path)
+                    change.remove_file(SourceRootId(root.0.into()), FileId(file.0.into()), path)
                 }
                 VfsChange::ChangeFile { file, text } => {
-                    change.change_file(FileId(file.0), text);
+                    change.change_file(FileId(file.0.into()), text);
                 }
             }
         }
@@ -173,18 +183,18 @@ impl ServerWorld {
             .read()
             .path2file(&path)
             .ok_or_else(|| format_err!("unknown file: {}", path.display()))?;
-        Ok(FileId(file.0))
+        Ok(FileId(file.0.into()))
     }
 
     pub fn file_id_to_uri(&self, id: FileId) -> Result<Url> {
-        let path = self.vfs.read().file2path(VfsFile(id.0));
+        let path = self.vfs.read().file2path(VfsFile(id.0.into()));
         let url = Url::from_file_path(&path)
             .map_err(|_| format_err!("can't convert path to url: {}", path.display()))?;
         Ok(url)
     }
 
     pub fn path_to_uri(&self, root: SourceRootId, path: &RelativePathBuf) -> Result<Url> {
-        let base = self.vfs.read().root2path(VfsRoot(root.0));
+        let base = self.vfs.read().root2path(VfsRoot(root.0.into()));
         let path = path.to_path(base);
         let url = Url::from_file_path(&path)
             .map_err(|_| format_err!("can't convert path to url: {}", path.display()))?;
diff --git a/crates/ra_vfs/Cargo.toml b/crates/ra_vfs/Cargo.toml
index 7c170cdfc..e637063c9 100644
--- a/crates/ra_vfs/Cargo.toml
+++ b/crates/ra_vfs/Cargo.toml
@@ -12,6 +12,7 @@ crossbeam-channel = "0.3.5"
 log = "0.4.6"
 
 thread_worker = { path = "../thread_worker" }
+ra_arena = { path = "../ra_arena" }
 
 [dev-dependencies]
 tempfile = "3"
diff --git a/crates/ra_vfs/src/arena.rs b/crates/ra_vfs/src/arena.rs
deleted file mode 100644
index 6b42ae26d..000000000
--- a/crates/ra_vfs/src/arena.rs
+++ /dev/null
@@ -1,53 +0,0 @@
-use std::{
-    marker::PhantomData,
-    ops::{Index, IndexMut},
-};
-
-#[derive(Clone, Debug)]
-pub(crate) struct Arena<ID: ArenaId, T> {
-    data: Vec<T>,
-    _ty: PhantomData<ID>,
-}
-
-pub(crate) trait ArenaId {
-    fn from_u32(id: u32) -> Self;
-    fn to_u32(self) -> u32;
-}
-
-impl<ID: ArenaId, T> Arena<ID, T> {
-    pub fn alloc(&mut self, value: T) -> ID {
-        let id = self.data.len() as u32;
-        self.data.push(value);
-        ID::from_u32(id)
-    }
-    pub fn iter<'a>(&'a self) -> impl Iterator<Item = (ID, &'a T)> {
-        self.data
-            .iter()
-            .enumerate()
-            .map(|(idx, value)| (ID::from_u32(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<ID: ArenaId, T> Index<ID> for Arena<ID, T> {
-    type Output = T;
-    fn index(&self, idx: ID) -> &T {
-        let idx = idx.to_u32() as usize;
-        &self.data[idx]
-    }
-}
-
-impl<ID: ArenaId, T> IndexMut<ID> for Arena<ID, T> {
-    fn index_mut(&mut self, idx: ID) -> &mut T {
-        let idx = idx.to_u32() as usize;
-        &mut self.data[idx]
-    }
-}
diff --git a/crates/ra_vfs/src/lib.rs b/crates/ra_vfs/src/lib.rs
index 5bbc3e993..cdea18d73 100644
--- a/crates/ra_vfs/src/lib.rs
+++ b/crates/ra_vfs/src/lib.rs
@@ -13,7 +13,6 @@
 //! VFS is based on a concept of roots: a set of directories on the file system
 //! which are watched for changes. Typically, there will be a root for each
 //! Cargo package.
-mod arena;
 mod io;
 
 use std::{
@@ -32,10 +31,7 @@ use relative_path::RelativePathBuf;
 use crossbeam_channel::Receiver;
 use walkdir::DirEntry;
 use thread_worker::WorkerHandle;
-
-use crate::{
-    arena::{ArenaId, Arena},
-};
+use ra_arena::{Arena, RawId, impl_arena_id};
 
 pub use crate::io::TaskResult as VfsTask;
 
@@ -68,29 +64,13 @@ fn has_rs_extension(p: &Path) -> bool {
     p.extension() == Some(OsStr::new("rs"))
 }
 
-#[derive(Clone, Copy, PartialEq, Eq, Debug, Hash)]
-pub struct VfsRoot(pub u32);
-
-impl ArenaId for VfsRoot {
-    fn from_u32(idx: u32) -> VfsRoot {
-        VfsRoot(idx)
-    }
-    fn to_u32(self) -> u32 {
-        self.0
-    }
-}
-
-#[derive(Clone, Copy, PartialEq, Eq, Debug, Hash)]
-pub struct VfsFile(pub u32);
+#[derive(Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash)]
+pub struct VfsRoot(pub RawId);
+impl_arena_id!(VfsRoot);
 
-impl ArenaId for VfsFile {
-    fn from_u32(idx: u32) -> VfsFile {
-        VfsFile(idx)
-    }
-    fn to_u32(self) -> u32 {
-        self.0
-    }
-}
+#[derive(Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash)]
+pub struct VfsFile(pub RawId);
+impl_arena_id!(VfsFile);
 
 struct VfsFileData {
     root: VfsRoot,