From f27b439786a4650bf8d1732187cccb8b7cd9d102 Mon Sep 17 00:00:00 2001
From: "Michael J. Klein" <lambdamichael@gmail.com>
Date: Tue, 30 Jan 2024 11:04:40 -0500
Subject: [PATCH 01/16] wip: remove dependency on generational-arena, add
 minimal vec-based arena class

---
 Cargo.lock                                    | 12 ----
 .../noirc_frontend/src/hir/def_map/mod.rs     |  2 +-
 .../noirc_frontend/src/hir/type_check/mod.rs  |  4 +-
 compiler/noirc_frontend/src/node_interner.rs  | 10 ++--
 compiler/utils/arena/Cargo.toml               |  5 --
 compiler/utils/arena/src/lib.rs               | 55 ++++++++++++++++++-
 6 files changed, 60 insertions(+), 28 deletions(-)

diff --git a/Cargo.lock b/Cargo.lock
index 93f1d25fc76..1dd62525954 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -213,9 +213,6 @@ checksum = "a4668cab20f66d8d020e1fbc0ebe47217433c1b6c8f2040faf858554e394ace6"
 [[package]]
 name = "arena"
 version = "0.23.0"
-dependencies = [
- "generational-arena",
-]
 
 [[package]]
 name = "ark-bls12-381"
@@ -1818,15 +1815,6 @@ dependencies = [
  "byteorder",
 ]
 
-[[package]]
-name = "generational-arena"
-version = "0.2.9"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "877e94aff08e743b651baaea359664321055749b398adff8740a7399af7796e7"
-dependencies = [
- "cfg-if 1.0.0",
-]
-
 [[package]]
 name = "generic-array"
 version = "0.14.7"
diff --git a/compiler/noirc_frontend/src/hir/def_map/mod.rs b/compiler/noirc_frontend/src/hir/def_map/mod.rs
index 8c985e88e0b..5fcc3101043 100644
--- a/compiler/noirc_frontend/src/hir/def_map/mod.rs
+++ b/compiler/noirc_frontend/src/hir/def_map/mod.rs
@@ -31,7 +31,7 @@ pub struct LocalModuleId(pub Index);
 
 impl LocalModuleId {
     pub fn dummy_id() -> LocalModuleId {
-        LocalModuleId(Index::from_raw_parts(std::usize::MAX, std::u64::MAX))
+        LocalModuleId(Index { ix: std::usize::MAX })
     }
 }
 
diff --git a/compiler/noirc_frontend/src/hir/type_check/mod.rs b/compiler/noirc_frontend/src/hir/type_check/mod.rs
index 3c2a970ee84..392f9222bd1 100644
--- a/compiler/noirc_frontend/src/hir/type_check/mod.rs
+++ b/compiler/noirc_frontend/src/hir/type_check/mod.rs
@@ -454,7 +454,7 @@ mod test {
         }
 
         fn local_module_id(&self) -> LocalModuleId {
-            LocalModuleId(arena::Index::from_raw_parts(0, 0))
+            LocalModuleId(arena::Index { ix: 0 })
         }
 
         fn module_id(&self) -> ModuleId {
@@ -505,7 +505,7 @@ mod test {
         let mut def_maps = BTreeMap::new();
         let file = FileId::default();
 
-        let mut modules = arena::Arena::new();
+        let mut modules = arena::Arena::default();
         let location = Location::new(Default::default(), file);
         modules.insert(ModuleData::new(None, location, false));
 
diff --git a/compiler/noirc_frontend/src/node_interner.rs b/compiler/noirc_frontend/src/node_interner.rs
index b856b54f6ca..d2e6134fd29 100644
--- a/compiler/noirc_frontend/src/node_interner.rs
+++ b/compiler/noirc_frontend/src/node_interner.rs
@@ -242,7 +242,7 @@ impl DefinitionId {
 
 impl From<DefinitionId> for Index {
     fn from(id: DefinitionId) -> Self {
-        Index::from_raw_parts(id.0, u64::MAX)
+        Index { ix: id.0 }
     }
 }
 
@@ -254,7 +254,7 @@ impl StmtId {
     // This can be anything, as the program will ultimately fail
     // after resolution
     pub fn dummy_id() -> StmtId {
-        StmtId(Index::from_raw_parts(std::usize::MAX, 0))
+        StmtId(Index { ix: std::usize::MAX })
     }
 }
 
@@ -263,7 +263,7 @@ pub struct ExprId(Index);
 
 impl ExprId {
     pub fn empty_block_id() -> ExprId {
-        ExprId(Index::from_raw_parts(0, 0))
+        ExprId(Index { ix: 0 })
     }
 }
 #[derive(Debug, Eq, PartialEq, Hash, Copy, Clone)]
@@ -274,7 +274,7 @@ impl FuncId {
     // This can be anything, as the program will ultimately fail
     // after resolution
     pub fn dummy_id() -> FuncId {
-        FuncId(Index::from_raw_parts(std::usize::MAX, 0))
+        FuncId(Index { ix: std::usize::MAX })
     }
 }
 
@@ -352,7 +352,7 @@ macro_rules! partialeq {
     ($id_type:ty) => {
         impl PartialEq<usize> for &$id_type {
             fn eq(&self, other: &usize) -> bool {
-                let (index, _) = self.0.into_raw_parts();
+                let index = self.0.ix;
                 index == *other
             }
         }
diff --git a/compiler/utils/arena/Cargo.toml b/compiler/utils/arena/Cargo.toml
index e82201a2cf4..41c6ebc9a8b 100644
--- a/compiler/utils/arena/Cargo.toml
+++ b/compiler/utils/arena/Cargo.toml
@@ -4,8 +4,3 @@ version.workspace = true
 authors.workspace = true
 edition.workspace = true
 license.workspace = true
-
-# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
-
-[dependencies]
-generational-arena = "0.2.8"
diff --git a/compiler/utils/arena/src/lib.rs b/compiler/utils/arena/src/lib.rs
index fc19f44ab6e..f15191639a9 100644
--- a/compiler/utils/arena/src/lib.rs
+++ b/compiler/utils/arena/src/lib.rs
@@ -1,7 +1,56 @@
 #![forbid(unsafe_code)]
-#![warn(unused_crate_dependencies, unused_extern_crates)]
 #![warn(unreachable_pub)]
 #![warn(clippy::semicolon_if_nothing_returned)]
 
-// For now we use a wrapper around generational-arena
-pub use generational_arena::{Arena, Index};
+#[derive(Clone, Copy, Debug, Eq, Ord, PartialEq, PartialOrd, Hash)]
+pub struct Index {
+    pub ix: usize,
+}
+
+#[derive(Debug, Eq, PartialEq, Hash, Clone)]
+pub struct Arena<T> {
+    vec: Vec<T>
+}
+
+impl<T> core::ops::Index<Index> for Arena<T> {
+    type Output = T;
+
+    fn index(&self, index: Index) -> &Self::Output {
+        self.vec.index(index.ix)
+    }
+}
+
+impl<T> core::ops::IndexMut<Index> for Arena<T> {
+    fn index_mut(&mut self, index: Index) -> &mut Self::Output {
+        self.vec.index_mut(index.ix)
+    }
+}
+
+impl<T> Arena<T> {
+    pub fn default() -> Self {
+        Self {
+            vec: Vec::new()
+        }
+    }
+
+    pub fn insert(&mut self, item: T) -> Index {
+        let ix = self.vec.len();
+        self.vec.push(item);
+        Index { ix }
+    }
+
+    pub fn get(&self, index: Index) -> Option<&T> {
+        self.vec.get(index.ix)
+    }
+
+    pub fn get_mut(&mut self, index: Index) -> Option<&mut T> {
+        self.vec.get_mut(index.ix)
+    }
+
+    pub fn iter(&self) -> impl Iterator<Item = (Index, &T)> {
+        self.vec.iter().enumerate().map(|(ix, item)| {
+            (Index { ix: ix }, item)
+        })
+    }
+}
+

From 7f95c26908d3beb533e55332413a5ac7e77b7392 Mon Sep 17 00:00:00 2001
From: "Michael J. Klein" <lambdamichael@gmail.com>
Date: Tue, 30 Jan 2024 11:06:38 -0500
Subject: [PATCH 02/16] cargo fmt

---
 compiler/utils/arena/src/lib.rs | 11 +++--------
 1 file changed, 3 insertions(+), 8 deletions(-)

diff --git a/compiler/utils/arena/src/lib.rs b/compiler/utils/arena/src/lib.rs
index f15191639a9..1336ce75384 100644
--- a/compiler/utils/arena/src/lib.rs
+++ b/compiler/utils/arena/src/lib.rs
@@ -9,7 +9,7 @@ pub struct Index {
 
 #[derive(Debug, Eq, PartialEq, Hash, Clone)]
 pub struct Arena<T> {
-    vec: Vec<T>
+    vec: Vec<T>,
 }
 
 impl<T> core::ops::Index<Index> for Arena<T> {
@@ -28,9 +28,7 @@ impl<T> core::ops::IndexMut<Index> for Arena<T> {
 
 impl<T> Arena<T> {
     pub fn default() -> Self {
-        Self {
-            vec: Vec::new()
-        }
+        Self { vec: Vec::new() }
     }
 
     pub fn insert(&mut self, item: T) -> Index {
@@ -48,9 +46,6 @@ impl<T> Arena<T> {
     }
 
     pub fn iter(&self) -> impl Iterator<Item = (Index, &T)> {
-        self.vec.iter().enumerate().map(|(ix, item)| {
-            (Index { ix: ix }, item)
-        })
+        self.vec.iter().enumerate().map(|(ix, item)| (Index { ix: ix }, item))
     }
 }
-

From da7e21999caf5648d568f833b874e05603ff6c6e Mon Sep 17 00:00:00 2001
From: "Michael J. Klein" <lambdamichael@gmail.com>
Date: Tue, 30 Jan 2024 11:21:04 -0500
Subject: [PATCH 03/16] cargo clippy

---
 compiler/utils/arena/src/lib.rs | 12 +++++++-----
 1 file changed, 7 insertions(+), 5 deletions(-)

diff --git a/compiler/utils/arena/src/lib.rs b/compiler/utils/arena/src/lib.rs
index 1336ce75384..910a7723fbe 100644
--- a/compiler/utils/arena/src/lib.rs
+++ b/compiler/utils/arena/src/lib.rs
@@ -12,6 +12,12 @@ pub struct Arena<T> {
     vec: Vec<T>,
 }
 
+impl<T> Default for Arena<T> {
+    fn default() -> Self {
+        Self { vec: Vec::new() }
+    }
+}
+
 impl<T> core::ops::Index<Index> for Arena<T> {
     type Output = T;
 
@@ -27,10 +33,6 @@ impl<T> core::ops::IndexMut<Index> for Arena<T> {
 }
 
 impl<T> Arena<T> {
-    pub fn default() -> Self {
-        Self { vec: Vec::new() }
-    }
-
     pub fn insert(&mut self, item: T) -> Index {
         let ix = self.vec.len();
         self.vec.push(item);
@@ -46,6 +48,6 @@ impl<T> Arena<T> {
     }
 
     pub fn iter(&self) -> impl Iterator<Item = (Index, &T)> {
-        self.vec.iter().enumerate().map(|(ix, item)| (Index { ix: ix }, item))
+        self.vec.iter().enumerate().map(|(ix, item)| (Index { ix }, item))
     }
 }

From f83698162e3c9284512fd098cd63a0c50ddf2e7b Mon Sep 17 00:00:00 2001
From: "Michael J. Klein" <lambdamichael@gmail.com>
Date: Tue, 30 Jan 2024 12:54:51 -0500
Subject: [PATCH 04/16] revert warnings for unused crates

---
 compiler/utils/arena/src/lib.rs | 1 +
 1 file changed, 1 insertion(+)

diff --git a/compiler/utils/arena/src/lib.rs b/compiler/utils/arena/src/lib.rs
index 910a7723fbe..615d9b59b14 100644
--- a/compiler/utils/arena/src/lib.rs
+++ b/compiler/utils/arena/src/lib.rs
@@ -1,4 +1,5 @@
 #![forbid(unsafe_code)]
+#![warn(unused_crate_dependencies, unused_extern_crates)]
 #![warn(unreachable_pub)]
 #![warn(clippy::semicolon_if_nothing_returned)]
 

From 9203fe5bf4186c4534b689a0ffc8af5809e65719 Mon Sep 17 00:00:00 2001
From: "Michael J. Klein" <lambdamichael@gmail.com>
Date: Tue, 30 Jan 2024 16:22:30 -0500
Subject: [PATCH 05/16] rename ix -> index

---
 compiler/noirc_frontend/src/hir/def_map/mod.rs |  2 +-
 compiler/noirc_frontend/src/node_interner.rs   | 10 +++++-----
 compiler/utils/arena/src/lib.rs                | 16 ++++++++--------
 3 files changed, 14 insertions(+), 14 deletions(-)

diff --git a/compiler/noirc_frontend/src/hir/def_map/mod.rs b/compiler/noirc_frontend/src/hir/def_map/mod.rs
index 5fcc3101043..3a4fca41d79 100644
--- a/compiler/noirc_frontend/src/hir/def_map/mod.rs
+++ b/compiler/noirc_frontend/src/hir/def_map/mod.rs
@@ -31,7 +31,7 @@ pub struct LocalModuleId(pub Index);
 
 impl LocalModuleId {
     pub fn dummy_id() -> LocalModuleId {
-        LocalModuleId(Index { ix: std::usize::MAX })
+        LocalModuleId(Index { index: std::usize::MAX })
     }
 }
 
diff --git a/compiler/noirc_frontend/src/node_interner.rs b/compiler/noirc_frontend/src/node_interner.rs
index d2e6134fd29..f990c330ed4 100644
--- a/compiler/noirc_frontend/src/node_interner.rs
+++ b/compiler/noirc_frontend/src/node_interner.rs
@@ -242,7 +242,7 @@ impl DefinitionId {
 
 impl From<DefinitionId> for Index {
     fn from(id: DefinitionId) -> Self {
-        Index { ix: id.0 }
+        Index { index: id.0 }
     }
 }
 
@@ -254,7 +254,7 @@ impl StmtId {
     // This can be anything, as the program will ultimately fail
     // after resolution
     pub fn dummy_id() -> StmtId {
-        StmtId(Index { ix: std::usize::MAX })
+        StmtId(Index { index: std::usize::MAX })
     }
 }
 
@@ -263,7 +263,7 @@ pub struct ExprId(Index);
 
 impl ExprId {
     pub fn empty_block_id() -> ExprId {
-        ExprId(Index { ix: 0 })
+        ExprId(Index { index: 0 })
     }
 }
 #[derive(Debug, Eq, PartialEq, Hash, Copy, Clone)]
@@ -274,7 +274,7 @@ impl FuncId {
     // This can be anything, as the program will ultimately fail
     // after resolution
     pub fn dummy_id() -> FuncId {
-        FuncId(Index { ix: std::usize::MAX })
+        FuncId(Index { index: std::usize::MAX })
     }
 }
 
@@ -352,7 +352,7 @@ macro_rules! partialeq {
     ($id_type:ty) => {
         impl PartialEq<usize> for &$id_type {
             fn eq(&self, other: &usize) -> bool {
-                let index = self.0.ix;
+                let index = self.0.index;
                 index == *other
             }
         }
diff --git a/compiler/utils/arena/src/lib.rs b/compiler/utils/arena/src/lib.rs
index 615d9b59b14..bfea3f11431 100644
--- a/compiler/utils/arena/src/lib.rs
+++ b/compiler/utils/arena/src/lib.rs
@@ -5,7 +5,7 @@
 
 #[derive(Clone, Copy, Debug, Eq, Ord, PartialEq, PartialOrd, Hash)]
 pub struct Index {
-    pub ix: usize,
+    pub index: usize,
 }
 
 #[derive(Debug, Eq, PartialEq, Hash, Clone)]
@@ -23,32 +23,32 @@ impl<T> core::ops::Index<Index> for Arena<T> {
     type Output = T;
 
     fn index(&self, index: Index) -> &Self::Output {
-        self.vec.index(index.ix)
+        self.vec.index(index.index)
     }
 }
 
 impl<T> core::ops::IndexMut<Index> for Arena<T> {
     fn index_mut(&mut self, index: Index) -> &mut Self::Output {
-        self.vec.index_mut(index.ix)
+        self.vec.index_mut(index.index)
     }
 }
 
 impl<T> Arena<T> {
     pub fn insert(&mut self, item: T) -> Index {
-        let ix = self.vec.len();
+        let index = self.vec.len();
         self.vec.push(item);
-        Index { ix }
+        Index { index }
     }
 
     pub fn get(&self, index: Index) -> Option<&T> {
-        self.vec.get(index.ix)
+        self.vec.get(index.index)
     }
 
     pub fn get_mut(&mut self, index: Index) -> Option<&mut T> {
-        self.vec.get_mut(index.ix)
+        self.vec.get_mut(index.index)
     }
 
     pub fn iter(&self) -> impl Iterator<Item = (Index, &T)> {
-        self.vec.iter().enumerate().map(|(ix, item)| (Index { ix }, item))
+        self.vec.iter().enumerate().map(|(index, item)| (Index { index }, item))
     }
 }

From 00531d218756e9f98748b904e373fa8b151f1d84 Mon Sep 17 00:00:00 2001
From: "Michael J. Klein" <lambdamichael@gmail.com>
Date: Wed, 31 Jan 2024 13:46:56 -0500
Subject: [PATCH 06/16] make Index a tuple struct

---
 compiler/noirc_frontend/src/hir/def_map/mod.rs |  2 +-
 compiler/noirc_frontend/src/node_interner.rs   | 10 +++++-----
 compiler/utils/arena/src/lib.rs                | 16 +++++++---------
 3 files changed, 13 insertions(+), 15 deletions(-)

diff --git a/compiler/noirc_frontend/src/hir/def_map/mod.rs b/compiler/noirc_frontend/src/hir/def_map/mod.rs
index 3a4fca41d79..5a22214095b 100644
--- a/compiler/noirc_frontend/src/hir/def_map/mod.rs
+++ b/compiler/noirc_frontend/src/hir/def_map/mod.rs
@@ -31,7 +31,7 @@ pub struct LocalModuleId(pub Index);
 
 impl LocalModuleId {
     pub fn dummy_id() -> LocalModuleId {
-        LocalModuleId(Index { index: std::usize::MAX })
+        LocalModuleId(Index(std::usize::MAX))
     }
 }
 
diff --git a/compiler/noirc_frontend/src/node_interner.rs b/compiler/noirc_frontend/src/node_interner.rs
index f990c330ed4..013cc04c2cd 100644
--- a/compiler/noirc_frontend/src/node_interner.rs
+++ b/compiler/noirc_frontend/src/node_interner.rs
@@ -242,7 +242,7 @@ impl DefinitionId {
 
 impl From<DefinitionId> for Index {
     fn from(id: DefinitionId) -> Self {
-        Index { index: id.0 }
+        Index(id.0)
     }
 }
 
@@ -254,7 +254,7 @@ impl StmtId {
     // This can be anything, as the program will ultimately fail
     // after resolution
     pub fn dummy_id() -> StmtId {
-        StmtId(Index { index: std::usize::MAX })
+        StmtId(Index(std::usize::MAX))
     }
 }
 
@@ -263,7 +263,7 @@ pub struct ExprId(Index);
 
 impl ExprId {
     pub fn empty_block_id() -> ExprId {
-        ExprId(Index { index: 0 })
+        ExprId(Index(0))
     }
 }
 #[derive(Debug, Eq, PartialEq, Hash, Copy, Clone)]
@@ -274,7 +274,7 @@ impl FuncId {
     // This can be anything, as the program will ultimately fail
     // after resolution
     pub fn dummy_id() -> FuncId {
-        FuncId(Index { index: std::usize::MAX })
+        FuncId(Index(std::usize::MAX))
     }
 }
 
@@ -352,7 +352,7 @@ macro_rules! partialeq {
     ($id_type:ty) => {
         impl PartialEq<usize> for &$id_type {
             fn eq(&self, other: &usize) -> bool {
-                let index = self.0.index;
+                let index = self.0 .0;
                 index == *other
             }
         }
diff --git a/compiler/utils/arena/src/lib.rs b/compiler/utils/arena/src/lib.rs
index bfea3f11431..a999e98c1c6 100644
--- a/compiler/utils/arena/src/lib.rs
+++ b/compiler/utils/arena/src/lib.rs
@@ -4,9 +4,7 @@
 #![warn(clippy::semicolon_if_nothing_returned)]
 
 #[derive(Clone, Copy, Debug, Eq, Ord, PartialEq, PartialOrd, Hash)]
-pub struct Index {
-    pub index: usize,
-}
+pub struct Index(pub usize);
 
 #[derive(Debug, Eq, PartialEq, Hash, Clone)]
 pub struct Arena<T> {
@@ -23,13 +21,13 @@ impl<T> core::ops::Index<Index> for Arena<T> {
     type Output = T;
 
     fn index(&self, index: Index) -> &Self::Output {
-        self.vec.index(index.index)
+        self.vec.index(index.0)
     }
 }
 
 impl<T> core::ops::IndexMut<Index> for Arena<T> {
     fn index_mut(&mut self, index: Index) -> &mut Self::Output {
-        self.vec.index_mut(index.index)
+        self.vec.index_mut(index.0)
     }
 }
 
@@ -37,18 +35,18 @@ impl<T> Arena<T> {
     pub fn insert(&mut self, item: T) -> Index {
         let index = self.vec.len();
         self.vec.push(item);
-        Index { index }
+        Index(index)
     }
 
     pub fn get(&self, index: Index) -> Option<&T> {
-        self.vec.get(index.index)
+        self.vec.get(index.0)
     }
 
     pub fn get_mut(&mut self, index: Index) -> Option<&mut T> {
-        self.vec.get_mut(index.index)
+        self.vec.get_mut(index.0)
     }
 
     pub fn iter(&self) -> impl Iterator<Item = (Index, &T)> {
-        self.vec.iter().enumerate().map(|(index, item)| (Index { index }, item))
+        self.vec.iter().enumerate().map(|(index, item)| (Index(index), item))
     }
 }

From b8098c8f4bdb471d248a4b8f96b6ec1fc651ffa6 Mon Sep 17 00:00:00 2001
From: kevaundray <kevtheappdev@gmail.com>
Date: Thu, 1 Feb 2024 12:29:31 +0000
Subject: [PATCH 07/16] Update
 compiler/noirc_frontend/src/hir/type_check/mod.rs

---
 compiler/noirc_frontend/src/hir/type_check/mod.rs | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/compiler/noirc_frontend/src/hir/type_check/mod.rs b/compiler/noirc_frontend/src/hir/type_check/mod.rs
index 392f9222bd1..d84ae304af4 100644
--- a/compiler/noirc_frontend/src/hir/type_check/mod.rs
+++ b/compiler/noirc_frontend/src/hir/type_check/mod.rs
@@ -454,7 +454,7 @@ mod test {
         }
 
         fn local_module_id(&self) -> LocalModuleId {
-            LocalModuleId(arena::Index { ix: 0 })
+            LocalModuleId(arena::Index(0))
         }
 
         fn module_id(&self) -> ModuleId {

From 151a23c15083618ce2c9d23380d825d12f97cde3 Mon Sep 17 00:00:00 2001
From: "Michael J. Klein" <lambdamichael@gmail.com>
Date: Mon, 5 Feb 2024 17:30:40 -0500
Subject: [PATCH 08/16] added back generational_arena, added copy of
 generational_arena::{Arena, Index} to {Arena, Index}, added tests for parity
 between arenas to class, added missing instances, found inconsistency, wip
 debugging

---
 Cargo.lock                                    |  13 ++
 compiler/noirc_frontend/Cargo.toml            |   1 +
 .../src/hir/def_collector/dc_mod.rs           |   6 +
 .../src/hir/def_map/item_scope.rs             |   2 +-
 .../noirc_frontend/src/hir/def_map/mod.rs     |   2 +-
 .../src/hir/def_map/module_data.rs            |   2 +-
 compiler/noirc_frontend/src/hir_def/expr.rs   |  30 ++---
 .../noirc_frontend/src/hir_def/function.rs    |   2 +-
 compiler/noirc_frontend/src/hir_def/stmt.rs   |  12 +-
 compiler/noirc_frontend/src/node_interner.rs  |  10 +-
 compiler/utils/arena/Cargo.toml               |   3 +
 compiler/utils/arena/src/lib.rs               | 119 +++++++++++++++---
 12 files changed, 155 insertions(+), 47 deletions(-)

diff --git a/Cargo.lock b/Cargo.lock
index e7f757776be..09cf969a686 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -213,6 +213,9 @@ checksum = "a4668cab20f66d8d020e1fbc0ebe47217433c1b6c8f2040faf858554e394ace6"
 [[package]]
 name = "arena"
 version = "0.23.0"
+dependencies = [
+ "generational-arena",
+]
 
 [[package]]
 name = "ark-bls12-381"
@@ -1815,6 +1818,15 @@ dependencies = [
  "byteorder",
 ]
 
+[[package]]
+name = "generational-arena"
+version = "0.2.9"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "877e94aff08e743b651baaea359664321055749b398adff8740a7399af7796e7"
+dependencies = [
+ "cfg-if 1.0.0",
+]
+
 [[package]]
 name = "generic-array"
 version = "0.14.7"
@@ -2969,6 +2981,7 @@ dependencies = [
  "arena",
  "chumsky",
  "fm",
+ "generational-arena",
  "iter-extended",
  "noirc_errors",
  "noirc_printable_type",
diff --git a/compiler/noirc_frontend/Cargo.toml b/compiler/noirc_frontend/Cargo.toml
index 80d767f7f2c..e63305885d7 100644
--- a/compiler/noirc_frontend/Cargo.toml
+++ b/compiler/noirc_frontend/Cargo.toml
@@ -23,6 +23,7 @@ rustc-hash = "1.1.0"
 small-ord-set = "0.1.3"
 regex = "1.9.1"
 tracing.workspace = true
+generational-arena = "0.2.8"
 
 [dev-dependencies]
 strum = "0.24"
diff --git a/compiler/noirc_frontend/src/hir/def_collector/dc_mod.rs b/compiler/noirc_frontend/src/hir/def_collector/dc_mod.rs
index 3cd60c33b8b..f6d861c3484 100644
--- a/compiler/noirc_frontend/src/hir/def_collector/dc_mod.rs
+++ b/compiler/noirc_frontend/src/hir/def_collector/dc_mod.rs
@@ -235,6 +235,9 @@ impl<'a> ModCollector<'a> {
             unresolved_functions.push_fn(self.module_id, func_id, function);
 
             // Add function to scope/ns of the module
+            // TODO: remove before merge
+            let _ = self.def_collector.def_map.modules._arena[self.module_id.0.1]
+                .declare_function(name.clone(), func_id);
             let result = self.def_collector.def_map.modules[self.module_id.0]
                 .declare_function(name, func_id);
 
@@ -408,6 +411,9 @@ impl<'a> ModCollector<'a> {
                             .def_interner
                             .push_function_definition(func_id, modifiers, trait_id.0, location);
 
+                        // TODO: remove before merge
+                        let _ = self.def_collector.def_map.modules._arena[trait_id.0.local_id.0.1]
+                            .declare_function(name.clone(), func_id);
                         match self.def_collector.def_map.modules[trait_id.0.local_id.0]
                             .declare_function(name.clone(), func_id)
                         {
diff --git a/compiler/noirc_frontend/src/hir/def_map/item_scope.rs b/compiler/noirc_frontend/src/hir/def_map/item_scope.rs
index 523def89518..50f1f50cbe5 100644
--- a/compiler/noirc_frontend/src/hir/def_map/item_scope.rs
+++ b/compiler/noirc_frontend/src/hir/def_map/item_scope.rs
@@ -12,7 +12,7 @@ pub enum Visibility {
     Public,
 }
 
-#[derive(Default, Debug, PartialEq, Eq)]
+#[derive(Clone, Default, Debug, PartialEq, Eq)]
 pub struct ItemScope {
     types: HashMap<Ident, Scope>,
     values: HashMap<Ident, Scope>,
diff --git a/compiler/noirc_frontend/src/hir/def_map/mod.rs b/compiler/noirc_frontend/src/hir/def_map/mod.rs
index 5a22214095b..65835eaa086 100644
--- a/compiler/noirc_frontend/src/hir/def_map/mod.rs
+++ b/compiler/noirc_frontend/src/hir/def_map/mod.rs
@@ -31,7 +31,7 @@ pub struct LocalModuleId(pub Index);
 
 impl LocalModuleId {
     pub fn dummy_id() -> LocalModuleId {
-        LocalModuleId(Index(std::usize::MAX))
+        LocalModuleId(Index(std::usize::MAX, generational_arena::Index::from_raw_parts(std::usize::MAX, 0)))
     }
 }
 
diff --git a/compiler/noirc_frontend/src/hir/def_map/module_data.rs b/compiler/noirc_frontend/src/hir/def_map/module_data.rs
index fbb5e5cf741..0f752d530bb 100644
--- a/compiler/noirc_frontend/src/hir/def_map/module_data.rs
+++ b/compiler/noirc_frontend/src/hir/def_map/module_data.rs
@@ -11,7 +11,7 @@ use super::{ItemScope, LocalModuleId, ModuleDefId, ModuleId, PerNs};
 
 /// Contains the actual contents of a module: its parent (if one exists),
 /// children, and scope with all definitions defined within the scope.
-#[derive(Debug, PartialEq, Eq)]
+#[derive(Clone, Debug, PartialEq, Eq)]
 pub struct ModuleData {
     pub parent: Option<LocalModuleId>,
     pub children: HashMap<Ident, LocalModuleId>,
diff --git a/compiler/noirc_frontend/src/hir_def/expr.rs b/compiler/noirc_frontend/src/hir_def/expr.rs
index 75ed68af0f6..70f53a24532 100644
--- a/compiler/noirc_frontend/src/hir_def/expr.rs
+++ b/compiler/noirc_frontend/src/hir_def/expr.rs
@@ -14,7 +14,7 @@ use super::types::{StructType, Type};
 /// references other HIR nodes indirectly via IDs rather than directly via
 /// boxing. Variables in HirExpressions are tagged with their DefinitionId
 /// from the definition that refers to them so there is no ambiguity with names.
-#[derive(Debug, Clone)]
+#[derive(Debug, Clone, PartialEq)]
 pub enum HirExpression {
     Ident(HirIdent),
     Literal(HirLiteral),
@@ -109,7 +109,7 @@ impl HirBinaryOp {
     }
 }
 
-#[derive(Debug, Clone)]
+#[derive(Debug, Clone, PartialEq)]
 pub enum HirLiteral {
     Array(HirArrayLiteral),
     Bool(bool),
@@ -119,19 +119,19 @@ pub enum HirLiteral {
     Unit,
 }
 
-#[derive(Debug, Clone)]
+#[derive(Debug, Clone, PartialEq)]
 pub enum HirArrayLiteral {
     Standard(Vec<ExprId>),
     Repeated { repeated_element: ExprId, length: Type },
 }
 
-#[derive(Debug, Clone)]
+#[derive(Debug, Clone, PartialEq)]
 pub struct HirPrefixExpression {
     pub operator: UnaryOp,
     pub rhs: ExprId,
 }
 
-#[derive(Debug, Clone)]
+#[derive(Debug, Clone, PartialEq)]
 pub struct HirInfixExpression {
     pub lhs: ExprId,
     pub operator: HirBinaryOp,
@@ -146,7 +146,7 @@ pub struct HirInfixExpression {
 
 /// This is always a struct field access `my_struct.field`
 /// and never a method call. The later is represented by HirMethodCallExpression.
-#[derive(Debug, Clone)]
+#[derive(Debug, Clone, PartialEq)]
 pub struct HirMemberAccess {
     pub lhs: ExprId,
     // This field is not an IdentId since the rhs of a field
@@ -160,7 +160,7 @@ pub struct HirMemberAccess {
     pub is_offset: bool,
 }
 
-#[derive(Debug, Clone)]
+#[derive(Debug, Clone, PartialEq)]
 pub struct HirIfExpression {
     pub condition: ExprId,
     pub consequence: ExprId,
@@ -168,13 +168,13 @@ pub struct HirIfExpression {
 }
 
 // `lhs as type` in the source code
-#[derive(Debug, Clone)]
+#[derive(Debug, Clone, PartialEq)]
 pub struct HirCastExpression {
     pub lhs: ExprId,
     pub r#type: Type,
 }
 
-#[derive(Debug, Clone)]
+#[derive(Debug, Clone, PartialEq)]
 pub struct HirCallExpression {
     pub func: ExprId,
     pub arguments: Vec<ExprId>,
@@ -185,7 +185,7 @@ pub struct HirCallExpression {
 /// lowered into HirCallExpression nodes
 /// after type checking resolves the object
 /// type and the method it calls.
-#[derive(Debug, Clone)]
+#[derive(Debug, Clone, PartialEq)]
 pub struct HirMethodCallExpression {
     pub method: Ident,
     pub object: ExprId,
@@ -239,7 +239,7 @@ impl HirMethodCallExpression {
     }
 }
 
-#[derive(Debug, Clone)]
+#[derive(Debug, Clone, PartialEq)]
 pub struct HirConstructorExpression {
     pub r#type: Shared<StructType>,
     pub struct_generics: Vec<Type>,
@@ -253,13 +253,13 @@ pub struct HirConstructorExpression {
 }
 
 /// Indexing, as in `array[index]`
-#[derive(Debug, Clone)]
+#[derive(Debug, Clone, PartialEq)]
 pub struct HirIndexExpression {
     pub collection: ExprId,
     pub index: ExprId,
 }
 
-#[derive(Debug, Clone)]
+#[derive(Debug, Clone, PartialEq)]
 pub struct HirBlockExpression(pub Vec<StmtId>);
 
 impl HirBlockExpression {
@@ -269,7 +269,7 @@ impl HirBlockExpression {
 }
 
 /// A variable captured inside a closure
-#[derive(Debug, Clone)]
+#[derive(Debug, Clone, PartialEq)]
 pub struct HirCapturedVar {
     pub ident: HirIdent,
 
@@ -283,7 +283,7 @@ pub struct HirCapturedVar {
     pub transitive_capture_index: Option<usize>,
 }
 
-#[derive(Debug, Clone)]
+#[derive(Debug, Clone, PartialEq)]
 pub struct HirLambda {
     pub parameters: Vec<(HirPattern, Type)>,
     pub return_type: Type,
diff --git a/compiler/noirc_frontend/src/hir_def/function.rs b/compiler/noirc_frontend/src/hir_def/function.rs
index 9fff301f5f7..81de6c65e6f 100644
--- a/compiler/noirc_frontend/src/hir_def/function.rs
+++ b/compiler/noirc_frontend/src/hir_def/function.rs
@@ -10,7 +10,7 @@ use crate::{Distinctness, FunctionReturnType, Type, Visibility};
 
 /// A Hir function is a block expression
 /// with a list of statements
-#[derive(Debug, Clone)]
+#[derive(Debug, Clone, PartialEq)]
 pub struct HirFunction(ExprId);
 
 impl HirFunction {
diff --git a/compiler/noirc_frontend/src/hir_def/stmt.rs b/compiler/noirc_frontend/src/hir_def/stmt.rs
index 4d946690151..d9cfbbce416 100644
--- a/compiler/noirc_frontend/src/hir_def/stmt.rs
+++ b/compiler/noirc_frontend/src/hir_def/stmt.rs
@@ -8,7 +8,7 @@ use noirc_errors::Span;
 /// the Statement AST node. Unlike the AST node, any nested nodes
 /// are referred to indirectly via ExprId or StmtId, which can be
 /// used to retrieve the relevant node via the NodeInterner.
-#[derive(Debug, Clone)]
+#[derive(Debug, Clone, PartialEq)]
 pub enum HirStatement {
     Let(HirLetStatement),
     Constrain(HirConstrainStatement),
@@ -19,7 +19,7 @@ pub enum HirStatement {
     Error,
 }
 
-#[derive(Debug, Clone)]
+#[derive(Debug, Clone, PartialEq)]
 pub struct HirLetStatement {
     pub pattern: HirPattern,
     pub r#type: Type,
@@ -35,7 +35,7 @@ impl HirLetStatement {
     }
 }
 
-#[derive(Debug, Clone)]
+#[derive(Debug, Clone, PartialEq)]
 pub struct HirForStatement {
     pub identifier: HirIdent,
     pub start_range: ExprId,
@@ -44,7 +44,7 @@ pub struct HirForStatement {
 }
 
 /// Corresponds to `lvalue = expression;` in the source code
-#[derive(Debug, Clone)]
+#[derive(Debug, Clone, PartialEq)]
 pub struct HirAssignStatement {
     pub lvalue: HirLValue,
     pub expression: ExprId,
@@ -54,10 +54,10 @@ pub struct HirAssignStatement {
 /// This node also contains the FileId of the file the constrain
 /// originates from. This is used later in the SSA pass to issue
 /// an error if a constrain is found to be always false.
-#[derive(Debug, Clone)]
+#[derive(Debug, Clone, PartialEq)]
 pub struct HirConstrainStatement(pub ExprId, pub FileId, pub Option<ExprId>);
 
-#[derive(Debug, Clone, Hash)]
+#[derive(Debug, Clone, Hash, PartialEq)]
 pub enum HirPattern {
     Identifier(HirIdent),
     Mutable(Box<HirPattern>, Span),
diff --git a/compiler/noirc_frontend/src/node_interner.rs b/compiler/noirc_frontend/src/node_interner.rs
index 013cc04c2cd..9822eec7ee5 100644
--- a/compiler/noirc_frontend/src/node_interner.rs
+++ b/compiler/noirc_frontend/src/node_interner.rs
@@ -242,7 +242,7 @@ impl DefinitionId {
 
 impl From<DefinitionId> for Index {
     fn from(id: DefinitionId) -> Self {
-        Index(id.0)
+        Index(id.0, generational_arena::Index::from_raw_parts(0, 0))
     }
 }
 
@@ -254,7 +254,7 @@ impl StmtId {
     // This can be anything, as the program will ultimately fail
     // after resolution
     pub fn dummy_id() -> StmtId {
-        StmtId(Index(std::usize::MAX))
+        StmtId(Index(std::usize::MAX, generational_arena::Index::from_raw_parts(std::usize::MAX, 0)))
     }
 }
 
@@ -263,7 +263,7 @@ pub struct ExprId(Index);
 
 impl ExprId {
     pub fn empty_block_id() -> ExprId {
-        ExprId(Index(0))
+        ExprId(Index(0, generational_arena::Index::from_raw_parts(0, 0)))
     }
 }
 #[derive(Debug, Eq, PartialEq, Hash, Copy, Clone)]
@@ -274,7 +274,7 @@ impl FuncId {
     // This can be anything, as the program will ultimately fail
     // after resolution
     pub fn dummy_id() -> FuncId {
-        FuncId(Index(std::usize::MAX))
+        FuncId(Index(std::usize::MAX, generational_arena::Index::from_raw_parts(std::usize::MAX, 0)))
     }
 }
 
@@ -369,7 +369,7 @@ partialeq!(StmtId);
 /// We use one Arena for all types that can be interned as that has better cache locality
 /// This data structure is never accessed directly, so API wise there is no difference between using
 /// Multiple arenas and a single Arena
-#[derive(Debug, Clone)]
+#[derive(Debug, Clone, PartialEq)]
 pub(crate) enum Node {
     Function(HirFunction),
     Statement(HirStatement),
diff --git a/compiler/utils/arena/Cargo.toml b/compiler/utils/arena/Cargo.toml
index 41c6ebc9a8b..ba4bbd0fa40 100644
--- a/compiler/utils/arena/Cargo.toml
+++ b/compiler/utils/arena/Cargo.toml
@@ -4,3 +4,6 @@ version.workspace = true
 authors.workspace = true
 edition.workspace = true
 license.workspace = true
+
+[dependencies]
+generational-arena = "0.2.8"
diff --git a/compiler/utils/arena/src/lib.rs b/compiler/utils/arena/src/lib.rs
index a999e98c1c6..8cf0910c685 100644
--- a/compiler/utils/arena/src/lib.rs
+++ b/compiler/utils/arena/src/lib.rs
@@ -4,49 +4,134 @@
 #![warn(clippy::semicolon_if_nothing_returned)]
 
 #[derive(Clone, Copy, Debug, Eq, Ord, PartialEq, PartialOrd, Hash)]
-pub struct Index(pub usize);
+// pub struct Index(pub usize);
+pub struct Index(pub usize, pub generational_arena::Index);
 
-#[derive(Debug, Eq, PartialEq, Hash, Clone)]
+// #[derive(Debug, Eq, PartialEq, Hash, Clone)]
+#[derive(Debug, Clone)]
 pub struct Arena<T> {
-    vec: Vec<T>,
+    pub vec: Vec<T>,
+    pub _arena: generational_arena::Arena<T>,
 }
 
 impl<T> Default for Arena<T> {
     fn default() -> Self {
-        Self { vec: Vec::new() }
+        Self {
+            vec: Vec::new(),
+            _arena: generational_arena::Arena::default(),
+        }
     }
 }
 
-impl<T> core::ops::Index<Index> for Arena<T> {
+
+impl<T> core::ops::Index<Index> for Arena<T>
+// TODO: remove
+where
+    T: PartialEq + std::fmt::Debug,
+{
     type Output = T;
 
     fn index(&self, index: Index) -> &Self::Output {
-        self.vec.index(index.0)
+        // self.vec.index(index.0)
+        let vec_out = self.vec.index(index.0);
+        let arena_out = self._arena.index(index.1);
+
+        if vec_out == arena_out {
+            vec_out
+        } else {
+            panic!("Arena::index: vec_out != arena_out:\n Index: {:?}\n \n {:?} != {:?}", index, vec_out, arena_out)
+        }
     }
 }
 
-impl<T> core::ops::IndexMut<Index> for Arena<T> {
+impl<T> core::ops::IndexMut<Index> for Arena<T>
+// TODO: remove
+where
+    T: PartialEq + std::fmt::Debug,
+{
     fn index_mut(&mut self, index: Index) -> &mut Self::Output {
-        self.vec.index_mut(index.0)
+        // self.vec.index_mut(index.0)
+        let vec_out = self.vec.get(index.0);
+        let arena_out = self._arena.get(index.1);
+
+        if vec_out == arena_out {
+            self.vec.index_mut(index.0)
+        } else {
+            let vec_iter = self.vec.iter().map(|x| format!("{:?}", x)).collect::<Vec<_>>().join("\n\n");
+            let arena_iter = self._arena.iter().map(|x| format!("{:?}", x.1)).collect::<Vec<_>>().join("\n\n");
+            panic!("Arena::index_mut: vec_out != arena_out:\n Index: {:?}\n \n {:?}\n !=\n {:?}\n\n Vec:\n{}\n\n Arena:\n{}", index, self.vec.get(index.0), self._arena.get(index.1), vec_iter, arena_iter)
+        }
     }
 }
 
+// TODO: remove Clone
 impl<T> Arena<T> {
-    pub fn insert(&mut self, item: T) -> Index {
+    pub fn insert(&mut self, item: T) -> Index
+    where
+        T: Clone + std::fmt::Debug,
+    {
         let index = self.vec.len();
-        self.vec.push(item);
-        Index(index)
+        self.vec.push(item.clone());
+
+        let index_arena = self._arena.insert(item);
+        if index == index_arena.into_raw_parts().0 {
+            Index(index, index_arena)
+        } else {
+            panic!("Arena::insert: index != index_arena: {:?} != {:?}", index, index_arena)
+        }
+
+        // Index(index)
     }
 
-    pub fn get(&self, index: Index) -> Option<&T> {
-        self.vec.get(index.0)
+    pub fn get(&self, index: Index) -> Option<&T>
+    where
+        T: PartialEq + std::fmt::Debug,
+    {
+        // self.vec.get(index.0)
+        let item = self.vec.get(index.0);
+        let item_arena = self._arena.get(index.1);
+        if item == item_arena {
+            item
+        } else {
+            panic!("Arena::get: {:?} != {:?}", item, item_arena)
+        }
     }
 
-    pub fn get_mut(&mut self, index: Index) -> Option<&mut T> {
-        self.vec.get_mut(index.0)
+    pub fn get_mut(&mut self, index: Index) -> Option<&mut T>
+    where
+        T: PartialEq + std::fmt::Debug,
+    {
+        // self.vec.get_mut(index.0)
+        let item = self.vec.get_mut(index.0);
+        let item_arena = self._arena.get_mut(index.1);
+        if item == item_arena {
+            item
+        } else {
+            panic!("Arena::get: {:?} != {:?}", item, item_arena)
+        }
     }
 
-    pub fn iter(&self) -> impl Iterator<Item = (Index, &T)> {
-        self.vec.iter().enumerate().map(|(index, item)| (Index(index), item))
+    pub fn iter(&self) -> impl Iterator<Item = (Index, &T)>
+    where
+        T: PartialEq + std::fmt::Debug,
+    {
+        // self.vec.iter().enumerate().map(|(index, item)| (Index(index), item))
+        self.vec
+            .iter()
+            .enumerate()
+            .map(|(index, item)| (Index(index, generational_arena::Index::from_raw_parts(index, 0)), item))
+            .zip(self._arena.iter())
+            .map(|(item, item_arena)| {
+                if item.0.0 == item_arena.0.into_raw_parts().0 && item.1 == item_arena.1 {
+                    Ok(item)
+                } else {
+                    Err(format!("Arena::iter: {:?} != {:?}", item, item_arena))
+                }
+            })
+            .collect::<Result<Vec<_>, _>>()
+            .unwrap()
+            .into_iter()
     }
+
 }
+

From 86d120eb5aec6d450c76f6ed62f1d47450d731ae Mon Sep 17 00:00:00 2001
From: "Michael J. Klein" <lambdamichael@gmail.com>
Date: Tue, 6 Feb 2024 15:48:41 -0500
Subject: [PATCH 09/16] wip debugging failing test

---
 .../src/hir/def_collector/dc_mod.rs           |  6 --
 .../noirc_frontend/src/hir/def_map/mod.rs     |  2 +-
 compiler/noirc_frontend/src/node_interner.rs  |  8 +-
 compiler/utils/arena/src/lib.rs               | 90 +++----------------
 4 files changed, 16 insertions(+), 90 deletions(-)

diff --git a/compiler/noirc_frontend/src/hir/def_collector/dc_mod.rs b/compiler/noirc_frontend/src/hir/def_collector/dc_mod.rs
index f6d861c3484..3cd60c33b8b 100644
--- a/compiler/noirc_frontend/src/hir/def_collector/dc_mod.rs
+++ b/compiler/noirc_frontend/src/hir/def_collector/dc_mod.rs
@@ -235,9 +235,6 @@ impl<'a> ModCollector<'a> {
             unresolved_functions.push_fn(self.module_id, func_id, function);
 
             // Add function to scope/ns of the module
-            // TODO: remove before merge
-            let _ = self.def_collector.def_map.modules._arena[self.module_id.0.1]
-                .declare_function(name.clone(), func_id);
             let result = self.def_collector.def_map.modules[self.module_id.0]
                 .declare_function(name, func_id);
 
@@ -411,9 +408,6 @@ impl<'a> ModCollector<'a> {
                             .def_interner
                             .push_function_definition(func_id, modifiers, trait_id.0, location);
 
-                        // TODO: remove before merge
-                        let _ = self.def_collector.def_map.modules._arena[trait_id.0.local_id.0.1]
-                            .declare_function(name.clone(), func_id);
                         match self.def_collector.def_map.modules[trait_id.0.local_id.0]
                             .declare_function(name.clone(), func_id)
                         {
diff --git a/compiler/noirc_frontend/src/hir/def_map/mod.rs b/compiler/noirc_frontend/src/hir/def_map/mod.rs
index 65835eaa086..aac19bd1a07 100644
--- a/compiler/noirc_frontend/src/hir/def_map/mod.rs
+++ b/compiler/noirc_frontend/src/hir/def_map/mod.rs
@@ -31,7 +31,7 @@ pub struct LocalModuleId(pub Index);
 
 impl LocalModuleId {
     pub fn dummy_id() -> LocalModuleId {
-        LocalModuleId(Index(std::usize::MAX, generational_arena::Index::from_raw_parts(std::usize::MAX, 0)))
+        LocalModuleId(Index(std::usize::MAX, generational_arena::Index::from_raw_parts(0,0)))
     }
 }
 
diff --git a/compiler/noirc_frontend/src/node_interner.rs b/compiler/noirc_frontend/src/node_interner.rs
index 9822eec7ee5..7dbf2ffcdac 100644
--- a/compiler/noirc_frontend/src/node_interner.rs
+++ b/compiler/noirc_frontend/src/node_interner.rs
@@ -242,7 +242,7 @@ impl DefinitionId {
 
 impl From<DefinitionId> for Index {
     fn from(id: DefinitionId) -> Self {
-        Index(id.0, generational_arena::Index::from_raw_parts(0, 0))
+        Index(id.0, generational_arena::Index::from_raw_parts(0,0))
     }
 }
 
@@ -254,7 +254,7 @@ impl StmtId {
     // This can be anything, as the program will ultimately fail
     // after resolution
     pub fn dummy_id() -> StmtId {
-        StmtId(Index(std::usize::MAX, generational_arena::Index::from_raw_parts(std::usize::MAX, 0)))
+        StmtId(Index(std::usize::MAX, generational_arena::Index::from_raw_parts(0,0)))
     }
 }
 
@@ -263,7 +263,7 @@ pub struct ExprId(Index);
 
 impl ExprId {
     pub fn empty_block_id() -> ExprId {
-        ExprId(Index(0, generational_arena::Index::from_raw_parts(0, 0)))
+        ExprId(Index(0, generational_arena::Index::from_raw_parts(0,0)))
     }
 }
 #[derive(Debug, Eq, PartialEq, Hash, Copy, Clone)]
@@ -274,7 +274,7 @@ impl FuncId {
     // This can be anything, as the program will ultimately fail
     // after resolution
     pub fn dummy_id() -> FuncId {
-        FuncId(Index(std::usize::MAX, generational_arena::Index::from_raw_parts(std::usize::MAX, 0)))
+        FuncId(Index(std::usize::MAX, generational_arena::Index::from_raw_parts(0,0)))
     }
 }
 
diff --git a/compiler/utils/arena/src/lib.rs b/compiler/utils/arena/src/lib.rs
index 8cf0910c685..8de117e6223 100644
--- a/compiler/utils/arena/src/lib.rs
+++ b/compiler/utils/arena/src/lib.rs
@@ -24,43 +24,17 @@ impl<T> Default for Arena<T> {
 }
 
 
-impl<T> core::ops::Index<Index> for Arena<T>
-// TODO: remove
-where
-    T: PartialEq + std::fmt::Debug,
-{
+impl<T> core::ops::Index<Index> for Arena<T> {
     type Output = T;
 
     fn index(&self, index: Index) -> &Self::Output {
-        // self.vec.index(index.0)
-        let vec_out = self.vec.index(index.0);
-        let arena_out = self._arena.index(index.1);
-
-        if vec_out == arena_out {
-            vec_out
-        } else {
-            panic!("Arena::index: vec_out != arena_out:\n Index: {:?}\n \n {:?} != {:?}", index, vec_out, arena_out)
-        }
+        self.vec.index(index.0)
     }
 }
 
-impl<T> core::ops::IndexMut<Index> for Arena<T>
-// TODO: remove
-where
-    T: PartialEq + std::fmt::Debug,
-{
+impl<T> core::ops::IndexMut<Index> for Arena<T> {
     fn index_mut(&mut self, index: Index) -> &mut Self::Output {
-        // self.vec.index_mut(index.0)
-        let vec_out = self.vec.get(index.0);
-        let arena_out = self._arena.get(index.1);
-
-        if vec_out == arena_out {
-            self.vec.index_mut(index.0)
-        } else {
-            let vec_iter = self.vec.iter().map(|x| format!("{:?}", x)).collect::<Vec<_>>().join("\n\n");
-            let arena_iter = self._arena.iter().map(|x| format!("{:?}", x.1)).collect::<Vec<_>>().join("\n\n");
-            panic!("Arena::index_mut: vec_out != arena_out:\n Index: {:?}\n \n {:?}\n !=\n {:?}\n\n Vec:\n{}\n\n Arena:\n{}", index, self.vec.get(index.0), self._arena.get(index.1), vec_iter, arena_iter)
-        }
+        self.vec.index_mut(index.0)
     }
 }
 
@@ -68,69 +42,27 @@ where
 impl<T> Arena<T> {
     pub fn insert(&mut self, item: T) -> Index
     where
-        T: Clone + std::fmt::Debug,
+        T: Clone,
     {
         let index = self.vec.len();
         self.vec.push(item.clone());
-
         let index_arena = self._arena.insert(item);
-        if index == index_arena.into_raw_parts().0 {
-            Index(index, index_arena)
-        } else {
-            panic!("Arena::insert: index != index_arena: {:?} != {:?}", index, index_arena)
-        }
-
-        // Index(index)
+        Index(index, index_arena)
     }
 
-    pub fn get(&self, index: Index) -> Option<&T>
-    where
-        T: PartialEq + std::fmt::Debug,
-    {
-        // self.vec.get(index.0)
-        let item = self.vec.get(index.0);
-        let item_arena = self._arena.get(index.1);
-        if item == item_arena {
-            item
-        } else {
-            panic!("Arena::get: {:?} != {:?}", item, item_arena)
-        }
+    pub fn get(&self, index: Index) -> Option<&T> {
+        self.vec.get(index.0)
     }
 
-    pub fn get_mut(&mut self, index: Index) -> Option<&mut T>
-    where
-        T: PartialEq + std::fmt::Debug,
-    {
-        // self.vec.get_mut(index.0)
-        let item = self.vec.get_mut(index.0);
-        let item_arena = self._arena.get_mut(index.1);
-        if item == item_arena {
-            item
-        } else {
-            panic!("Arena::get: {:?} != {:?}", item, item_arena)
-        }
+    pub fn get_mut(&mut self, index: Index) -> Option<&mut T> {
+        self.vec.get_mut(index.0)
     }
 
-    pub fn iter(&self) -> impl Iterator<Item = (Index, &T)>
-    where
-        T: PartialEq + std::fmt::Debug,
-    {
-        // self.vec.iter().enumerate().map(|(index, item)| (Index(index), item))
+    pub fn iter(&self) -> impl Iterator<Item = (Index, &T)> {
         self.vec
             .iter()
             .enumerate()
             .map(|(index, item)| (Index(index, generational_arena::Index::from_raw_parts(index, 0)), item))
-            .zip(self._arena.iter())
-            .map(|(item, item_arena)| {
-                if item.0.0 == item_arena.0.into_raw_parts().0 && item.1 == item_arena.1 {
-                    Ok(item)
-                } else {
-                    Err(format!("Arena::iter: {:?} != {:?}", item, item_arena))
-                }
-            })
-            .collect::<Result<Vec<_>, _>>()
-            .unwrap()
-            .into_iter()
     }
 
 }

From cd279cd0d096261cbe82aa6160fd384e7bb0aefe Mon Sep 17 00:00:00 2001
From: Jake Fecher <jfecher11@gmail.com>
Date: Mon, 12 Feb 2024 13:20:30 -0600
Subject: [PATCH 10/16] Fix compile errors from aztec_macros

---
 aztec_macros/src/lib.rs         |  2 +-
 compiler/utils/arena/src/lib.rs | 20 ++++++++++++++++++++
 2 files changed, 21 insertions(+), 1 deletion(-)

diff --git a/aztec_macros/src/lib.rs b/aztec_macros/src/lib.rs
index 7ca4b79eed8..82a9744de5d 100644
--- a/aztec_macros/src/lib.rs
+++ b/aztec_macros/src/lib.rs
@@ -696,7 +696,7 @@ fn collect_traits(context: &HirContext) -> Vec<TraitId> {
     crates
         .flat_map(|crate_id| context.def_map(&crate_id).map(|def_map| def_map.modules()))
         .flatten()
-        .flat_map(|(_, module)| {
+        .flat_map(|module| {
             module.type_definitions().filter_map(|typ| {
                 if let ModuleDefId::TraitId(struct_id) = typ {
                     Some(struct_id)
diff --git a/compiler/utils/arena/src/lib.rs b/compiler/utils/arena/src/lib.rs
index 8de117e6223..354105a56b6 100644
--- a/compiler/utils/arena/src/lib.rs
+++ b/compiler/utils/arena/src/lib.rs
@@ -38,6 +38,26 @@ impl<T> core::ops::IndexMut<Index> for Arena<T> {
     }
 }
 
+impl<T> IntoIterator for Arena<T> {
+    type Item = T;
+
+    type IntoIter = <Vec<T> as IntoIterator>::IntoIter;
+
+    fn into_iter(self) -> Self::IntoIter {
+        self.vec.into_iter()
+    }
+}
+
+impl<'a, T> IntoIterator for &'a Arena<T> {
+    type Item = &'a T;
+
+    type IntoIter = <&'a Vec<T> as IntoIterator>::IntoIter;
+
+    fn into_iter(self) -> Self::IntoIter {
+        self.vec.iter()
+    }
+}
+
 // TODO: remove Clone
 impl<T> Arena<T> {
     pub fn insert(&mut self, item: T) -> Index

From ed62fd790856bf72adba4ef300d4b2d550cd5768 Mon Sep 17 00:00:00 2001
From: Jake Fecher <jfecher11@gmail.com>
Date: Mon, 12 Feb 2024 13:53:08 -0600
Subject: [PATCH 11/16] Fmt

---
 compiler/noirc_frontend/src/hir/def_map/mod.rs |  2 +-
 compiler/noirc_frontend/src/node_interner.rs   |  8 ++++----
 compiler/utils/arena/src/lib.rs                | 15 ++++-----------
 3 files changed, 9 insertions(+), 16 deletions(-)

diff --git a/compiler/noirc_frontend/src/hir/def_map/mod.rs b/compiler/noirc_frontend/src/hir/def_map/mod.rs
index aac19bd1a07..5fa44b3dd15 100644
--- a/compiler/noirc_frontend/src/hir/def_map/mod.rs
+++ b/compiler/noirc_frontend/src/hir/def_map/mod.rs
@@ -31,7 +31,7 @@ pub struct LocalModuleId(pub Index);
 
 impl LocalModuleId {
     pub fn dummy_id() -> LocalModuleId {
-        LocalModuleId(Index(std::usize::MAX, generational_arena::Index::from_raw_parts(0,0)))
+        LocalModuleId(Index(std::usize::MAX, generational_arena::Index::from_raw_parts(0, 0)))
     }
 }
 
diff --git a/compiler/noirc_frontend/src/node_interner.rs b/compiler/noirc_frontend/src/node_interner.rs
index 62f91c11939..46381b59cd0 100644
--- a/compiler/noirc_frontend/src/node_interner.rs
+++ b/compiler/noirc_frontend/src/node_interner.rs
@@ -278,7 +278,7 @@ impl DefinitionId {
 
 impl From<DefinitionId> for Index {
     fn from(id: DefinitionId) -> Self {
-        Index(id.0, generational_arena::Index::from_raw_parts(0,0))
+        Index(id.0, generational_arena::Index::from_raw_parts(0, 0))
     }
 }
 
@@ -301,7 +301,7 @@ impl StmtId {
     // This can be anything, as the program will ultimately fail
     // after resolution
     pub fn dummy_id() -> StmtId {
-        StmtId(Index(std::usize::MAX, generational_arena::Index::from_raw_parts(0,0)))
+        StmtId(Index(std::usize::MAX, generational_arena::Index::from_raw_parts(0, 0)))
     }
 }
 
@@ -310,7 +310,7 @@ pub struct ExprId(Index);
 
 impl ExprId {
     pub fn empty_block_id() -> ExprId {
-        ExprId(Index(0, generational_arena::Index::from_raw_parts(0,0)))
+        ExprId(Index(0, generational_arena::Index::from_raw_parts(0, 0)))
     }
 }
 #[derive(Debug, Eq, PartialEq, Hash, Copy, Clone)]
@@ -321,7 +321,7 @@ impl FuncId {
     // This can be anything, as the program will ultimately fail
     // after resolution
     pub fn dummy_id() -> FuncId {
-        FuncId(Index(std::usize::MAX, generational_arena::Index::from_raw_parts(0,0)))
+        FuncId(Index(std::usize::MAX, generational_arena::Index::from_raw_parts(0, 0)))
     }
 }
 
diff --git a/compiler/utils/arena/src/lib.rs b/compiler/utils/arena/src/lib.rs
index 354105a56b6..75593e26f63 100644
--- a/compiler/utils/arena/src/lib.rs
+++ b/compiler/utils/arena/src/lib.rs
@@ -16,14 +16,10 @@ pub struct Arena<T> {
 
 impl<T> Default for Arena<T> {
     fn default() -> Self {
-        Self {
-            vec: Vec::new(),
-            _arena: generational_arena::Arena::default(),
-        }
+        Self { vec: Vec::new(), _arena: generational_arena::Arena::default() }
     }
 }
 
-
 impl<T> core::ops::Index<Index> for Arena<T> {
     type Output = T;
 
@@ -79,11 +75,8 @@ impl<T> Arena<T> {
     }
 
     pub fn iter(&self) -> impl Iterator<Item = (Index, &T)> {
-        self.vec
-            .iter()
-            .enumerate()
-            .map(|(index, item)| (Index(index, generational_arena::Index::from_raw_parts(index, 0)), item))
+        self.vec.iter().enumerate().map(|(index, item)| {
+            (Index(index, generational_arena::Index::from_raw_parts(index, 0)), item)
+        })
     }
-
 }
-

From 0f4f32df3309b2abedd8eb646fe90686541d3fe4 Mon Sep 17 00:00:00 2001
From: Jake Fecher <jfecher11@gmail.com>
Date: Mon, 12 Feb 2024 14:30:06 -0600
Subject: [PATCH 12/16] Fix frontend test

---
 compiler/noirc_frontend/src/hir/type_check/mod.rs | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/compiler/noirc_frontend/src/hir/type_check/mod.rs b/compiler/noirc_frontend/src/hir/type_check/mod.rs
index b6edb74609b..4dcddbcca02 100644
--- a/compiler/noirc_frontend/src/hir/type_check/mod.rs
+++ b/compiler/noirc_frontend/src/hir/type_check/mod.rs
@@ -458,7 +458,7 @@ mod test {
         }
 
         fn local_module_id(&self) -> LocalModuleId {
-            LocalModuleId(arena::Index(0))
+            LocalModuleId(arena::Index(0, generational_arena::Index::from_raw_parts(0, 0)))
         }
 
         fn module_id(&self) -> ModuleId {

From aa35b34b92c92bb9446b26c553e09da07aca0a22 Mon Sep 17 00:00:00 2001
From: "Michael J. Klein" <lambdamichael@gmail.com>
Date: Tue, 13 Feb 2024 17:46:21 -0500
Subject: [PATCH 13/16] remove generational arena test stubs, indices, etc

---
 Cargo.lock                                     | 13 -------------
 Cargo.toml                                     |  4 ----
 compiler/noirc_frontend/Cargo.toml             |  1 -
 compiler/noirc_frontend/src/hir/def_map/mod.rs |  2 +-
 compiler/noirc_frontend/src/node_interner.rs   |  8 ++++----
 compiler/utils/arena/Cargo.toml                |  3 ---
 compiler/utils/arena/src/lib.rs                | 11 ++++-------
 7 files changed, 9 insertions(+), 33 deletions(-)

diff --git a/Cargo.lock b/Cargo.lock
index ddbecdd822e..4d8b12d5379 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -213,9 +213,6 @@ checksum = "a4668cab20f66d8d020e1fbc0ebe47217433c1b6c8f2040faf858554e394ace6"
 [[package]]
 name = "arena"
 version = "0.24.0"
-dependencies = [
- "generational-arena",
-]
 
 [[package]]
 name = "ark-bls12-381"
@@ -1842,15 +1839,6 @@ dependencies = [
  "byteorder",
 ]
 
-[[package]]
-name = "generational-arena"
-version = "0.2.9"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "877e94aff08e743b651baaea359664321055749b398adff8740a7399af7796e7"
-dependencies = [
- "cfg-if 1.0.0",
-]
-
 [[package]]
 name = "generic-array"
 version = "0.14.7"
@@ -3004,7 +2992,6 @@ dependencies = [
  "arena",
  "chumsky",
  "fm",
- "generational-arena",
  "iter-extended",
  "noirc_errors",
  "noirc_printable_type",
diff --git a/Cargo.toml b/Cargo.toml
index 4f95e3b0821..77058554aff 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -69,12 +69,10 @@ noirc_errors = { path = "compiler/noirc_errors" }
 noirc_evaluator = { path = "compiler/noirc_evaluator" }
 noirc_frontend = { path = "compiler/noirc_frontend" }
 noirc_printable_type = { path = "compiler/noirc_printable_type" }
-noir_wasm = { path = "compiler/wasm" }
 
 # Noir tooling workspace dependencies
 nargo = { path = "tooling/nargo" }
 nargo_fmt = { path = "tooling/nargo_fmt" }
-nargo_cli = { path = "tooling/nargo_cli" }
 nargo_toml = { path = "tooling/nargo_toml" }
 noir_lsp = { path = "tooling/lsp" }
 noir_debugger = { path = "tooling/debugger" }
@@ -97,8 +95,6 @@ getrandom = "0.2"
 
 # Debugger
 dap = "0.4.1-alpha1"
-
-cfg-if = "1.0.0"
 clap = { version = "4.3.19", features = ["derive", "env"] }
 codespan = { version = "0.11.1", features = ["serialization"] }
 codespan-lsp = "0.11.1"
diff --git a/compiler/noirc_frontend/Cargo.toml b/compiler/noirc_frontend/Cargo.toml
index 40bb44b9455..a3a8d460572 100644
--- a/compiler/noirc_frontend/Cargo.toml
+++ b/compiler/noirc_frontend/Cargo.toml
@@ -23,7 +23,6 @@ rustc-hash = "1.1.0"
 small-ord-set = "0.1.3"
 regex = "1.9.1"
 tracing.workspace = true
-generational-arena = "0.2.8"
 petgraph = "0.6"
 
 [dev-dependencies]
diff --git a/compiler/noirc_frontend/src/hir/def_map/mod.rs b/compiler/noirc_frontend/src/hir/def_map/mod.rs
index 5fa44b3dd15..5a22214095b 100644
--- a/compiler/noirc_frontend/src/hir/def_map/mod.rs
+++ b/compiler/noirc_frontend/src/hir/def_map/mod.rs
@@ -31,7 +31,7 @@ pub struct LocalModuleId(pub Index);
 
 impl LocalModuleId {
     pub fn dummy_id() -> LocalModuleId {
-        LocalModuleId(Index(std::usize::MAX, generational_arena::Index::from_raw_parts(0, 0)))
+        LocalModuleId(Index(std::usize::MAX))
     }
 }
 
diff --git a/compiler/noirc_frontend/src/node_interner.rs b/compiler/noirc_frontend/src/node_interner.rs
index abd39c665de..87542b1b9f8 100644
--- a/compiler/noirc_frontend/src/node_interner.rs
+++ b/compiler/noirc_frontend/src/node_interner.rs
@@ -278,7 +278,7 @@ impl DefinitionId {
 
 impl From<DefinitionId> for Index {
     fn from(id: DefinitionId) -> Self {
-        Index(id.0, generational_arena::Index::from_raw_parts(0, 0))
+        Index(id.0)
     }
 }
 
@@ -301,7 +301,7 @@ impl StmtId {
     // This can be anything, as the program will ultimately fail
     // after resolution
     pub fn dummy_id() -> StmtId {
-        StmtId(Index(std::usize::MAX, generational_arena::Index::from_raw_parts(0, 0)))
+        StmtId(Index(std::usize::MAX))
     }
 }
 
@@ -310,7 +310,7 @@ pub struct ExprId(Index);
 
 impl ExprId {
     pub fn empty_block_id() -> ExprId {
-        ExprId(Index(0, generational_arena::Index::from_raw_parts(0, 0)))
+        ExprId(Index(0))
     }
 }
 #[derive(Debug, Eq, PartialEq, Hash, Copy, Clone)]
@@ -321,7 +321,7 @@ impl FuncId {
     // This can be anything, as the program will ultimately fail
     // after resolution
     pub fn dummy_id() -> FuncId {
-        FuncId(Index(std::usize::MAX, generational_arena::Index::from_raw_parts(0, 0)))
+        FuncId(Index(std::usize::MAX))
     }
 }
 
diff --git a/compiler/utils/arena/Cargo.toml b/compiler/utils/arena/Cargo.toml
index ba4bbd0fa40..41c6ebc9a8b 100644
--- a/compiler/utils/arena/Cargo.toml
+++ b/compiler/utils/arena/Cargo.toml
@@ -4,6 +4,3 @@ version.workspace = true
 authors.workspace = true
 edition.workspace = true
 license.workspace = true
-
-[dependencies]
-generational-arena = "0.2.8"
diff --git a/compiler/utils/arena/src/lib.rs b/compiler/utils/arena/src/lib.rs
index 75593e26f63..158c9c1fa9d 100644
--- a/compiler/utils/arena/src/lib.rs
+++ b/compiler/utils/arena/src/lib.rs
@@ -4,19 +4,17 @@
 #![warn(clippy::semicolon_if_nothing_returned)]
 
 #[derive(Clone, Copy, Debug, Eq, Ord, PartialEq, PartialOrd, Hash)]
-// pub struct Index(pub usize);
-pub struct Index(pub usize, pub generational_arena::Index);
+pub struct Index(pub usize);
 
 // #[derive(Debug, Eq, PartialEq, Hash, Clone)]
 #[derive(Debug, Clone)]
 pub struct Arena<T> {
     pub vec: Vec<T>,
-    pub _arena: generational_arena::Arena<T>,
 }
 
 impl<T> Default for Arena<T> {
     fn default() -> Self {
-        Self { vec: Vec::new(), _arena: generational_arena::Arena::default() }
+        Self { vec: Vec::new() }
     }
 }
 
@@ -62,8 +60,7 @@ impl<T> Arena<T> {
     {
         let index = self.vec.len();
         self.vec.push(item.clone());
-        let index_arena = self._arena.insert(item);
-        Index(index, index_arena)
+        Index(index)
     }
 
     pub fn get(&self, index: Index) -> Option<&T> {
@@ -76,7 +73,7 @@ impl<T> Arena<T> {
 
     pub fn iter(&self) -> impl Iterator<Item = (Index, &T)> {
         self.vec.iter().enumerate().map(|(index, item)| {
-            (Index(index, generational_arena::Index::from_raw_parts(index, 0)), item)
+            (Index(index), item)
         })
     }
 }

From 68d7cb6088795b8e919b4e20a7f5adc2262b9c91 Mon Sep 17 00:00:00 2001
From: "Michael J. Klein" <lambdamichael@gmail.com>
Date: Tue, 13 Feb 2024 17:52:24 -0500
Subject: [PATCH 14/16] cargo fmt

---
 compiler/utils/arena/src/lib.rs | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/compiler/utils/arena/src/lib.rs b/compiler/utils/arena/src/lib.rs
index 158c9c1fa9d..cf834ed7d59 100644
--- a/compiler/utils/arena/src/lib.rs
+++ b/compiler/utils/arena/src/lib.rs
@@ -72,8 +72,6 @@ impl<T> Arena<T> {
     }
 
     pub fn iter(&self) -> impl Iterator<Item = (Index, &T)> {
-        self.vec.iter().enumerate().map(|(index, item)| {
-            (Index(index), item)
-        })
+        self.vec.iter().enumerate().map(|(index, item)| (Index(index), item))
     }
 }

From e49fde456eb10468abcef132e4bdcbdde038c0e4 Mon Sep 17 00:00:00 2001
From: jfecher <jake@aztecprotocol.com>
Date: Fri, 16 Feb 2024 13:06:59 -0600
Subject: [PATCH 15/16] fix: DefinitionIds should not be stored in id_to_type
 (#4397)

# Description

## Problem\*

Resolves the underlying issue with #4207 where definition/expr types are
being overwritten by other exprs/definitions because DefinitionIds are
converted into Indexes which may clash with those from expressions.

## Summary\*

Separates out `id_to_type` into another map for only definitions:
`definition_to_type` to resolve the clash. I've also removed the `impl
From<DefinitionId> for Index` to prevent this issue in the future.

## Additional Context



## Documentation\*

Check one:
- [x] No documentation needed.
- [ ] Documentation included in this PR.
- [ ] **[Exceptional Case]** Documentation to be submitted in a separate
PR.

# PR Checklist\*

- [x] I have tested the changes locally.
- [x] I have formatted the changes with [Prettier](https://prettier.io/)
and/or `cargo fmt` on default settings.
---
 aztec_macros/src/lib.rs                       |  7 +--
 .../noirc_frontend/src/hir/def_map/mod.rs     |  2 +-
 .../src/hir/resolution/resolver.rs            |  2 +-
 .../noirc_frontend/src/hir/type_check/expr.rs | 15 ++---
 .../noirc_frontend/src/hir/type_check/mod.rs  |  2 +-
 .../noirc_frontend/src/hir/type_check/stmt.rs |  2 +-
 compiler/noirc_frontend/src/hir_def/types.rs  |  9 ++-
 .../src/monomorphization/debug.rs             |  4 +-
 .../src/monomorphization/mod.rs               |  4 +-
 compiler/noirc_frontend/src/node_interner.rs  | 57 +++++++------------
 compiler/utils/arena/src/lib.rs               | 21 ++++++-
 11 files changed, 65 insertions(+), 60 deletions(-)

diff --git a/aztec_macros/src/lib.rs b/aztec_macros/src/lib.rs
index 14b1cedf5f3..9eb60ebede7 100644
--- a/aztec_macros/src/lib.rs
+++ b/aztec_macros/src/lib.rs
@@ -763,11 +763,11 @@ fn transform_event(
         HirExpression::Literal(HirLiteral::Str(signature))
             if signature == SIGNATURE_PLACEHOLDER =>
         {
-            let selector_literal_id = first_arg_id;
+            let selector_literal_id = *first_arg_id;
 
             let structure = interner.get_struct(struct_id);
             let signature = event_signature(&structure.borrow());
-            interner.update_expression(*selector_literal_id, |expr| {
+            interner.update_expression(selector_literal_id, |expr| {
                 *expr = HirExpression::Literal(HirLiteral::Str(signature.clone()));
             });
 
@@ -833,7 +833,7 @@ fn get_serialized_length(
 
     let serialized_trait_impl_kind = traits
         .iter()
-        .filter_map(|&trait_id| {
+        .find_map(|&trait_id| {
             let r#trait = interner.get_trait(trait_id);
             if r#trait.borrow().name.0.contents == "Serialize"
                 && r#trait.borrow().generics.len() == 1
@@ -846,7 +846,6 @@ fn get_serialized_length(
                 None
             }
         })
-        .next()
         .ok_or(AztecMacroError::CouldNotAssignStorageSlots {
             secondary_message: Some("Stored data must implement Serialize trait".to_string()),
         })?;
diff --git a/compiler/noirc_frontend/src/hir/def_map/mod.rs b/compiler/noirc_frontend/src/hir/def_map/mod.rs
index 5a22214095b..8e0dacc294b 100644
--- a/compiler/noirc_frontend/src/hir/def_map/mod.rs
+++ b/compiler/noirc_frontend/src/hir/def_map/mod.rs
@@ -31,7 +31,7 @@ pub struct LocalModuleId(pub Index);
 
 impl LocalModuleId {
     pub fn dummy_id() -> LocalModuleId {
-        LocalModuleId(Index(std::usize::MAX))
+        LocalModuleId(Index::dummy())
     }
 }
 
diff --git a/compiler/noirc_frontend/src/hir/resolution/resolver.rs b/compiler/noirc_frontend/src/hir/resolution/resolver.rs
index d4aae133b35..f05a69be7c2 100644
--- a/compiler/noirc_frontend/src/hir/resolution/resolver.rs
+++ b/compiler/noirc_frontend/src/hir/resolution/resolver.rs
@@ -1463,7 +1463,7 @@ impl<'a> Resolver<'a> {
                                 // they're used in expressions. We must do this here since the type
                                 // checker does not check definition kinds and otherwise expects
                                 // parameters to already be typed.
-                                if self.interner.id_type(hir_ident.id) == Type::Error {
+                                if self.interner.definition_type(hir_ident.id) == Type::Error {
                                     let typ = Type::polymorphic_integer(self.interner);
                                     self.interner.push_definition_type(hir_ident.id, typ);
                                 }
diff --git a/compiler/noirc_frontend/src/hir/type_check/expr.rs b/compiler/noirc_frontend/src/hir/type_check/expr.rs
index 96a79152f69..26084931bd2 100644
--- a/compiler/noirc_frontend/src/hir/type_check/expr.rs
+++ b/compiler/noirc_frontend/src/hir/type_check/expr.rs
@@ -284,8 +284,9 @@ impl<'interner> TypeChecker<'interner> {
                 Type::Tuple(vecmap(&elements, |elem| self.check_expression(elem)))
             }
             HirExpression::Lambda(lambda) => {
-                let captured_vars =
-                    vecmap(lambda.captures, |capture| self.interner.id_type(capture.ident.id));
+                let captured_vars = vecmap(lambda.captures, |capture| {
+                    self.interner.definition_type(capture.ident.id)
+                });
 
                 let env_type: Type =
                     if captured_vars.is_empty() { Type::Unit } else { Type::Tuple(captured_vars) };
@@ -308,7 +309,7 @@ impl<'interner> TypeChecker<'interner> {
             }
         };
 
-        self.interner.push_expr_type(expr_id, typ.clone());
+        self.interner.push_expr_type(*expr_id, typ.clone());
         typ
     }
 
@@ -459,7 +460,7 @@ impl<'interner> TypeChecker<'interner> {
                                 operator: UnaryOp::MutableReference,
                                 rhs: method_call.object,
                             }));
-                        self.interner.push_expr_type(&new_object, new_type);
+                        self.interner.push_expr_type(new_object, new_type);
                         self.interner.push_expr_location(new_object, location.span, location.file);
                         new_object
                     });
@@ -485,7 +486,7 @@ impl<'interner> TypeChecker<'interner> {
                 operator: UnaryOp::Dereference { implicitly_added: true },
                 rhs: object,
             }));
-            self.interner.push_expr_type(&object, element.as_ref().clone());
+            self.interner.push_expr_type(object, element.as_ref().clone());
             self.interner.push_expr_location(object, location.span, location.file);
 
             // Recursively dereference to allow for converting &mut &mut T to T
@@ -682,8 +683,8 @@ impl<'interner> TypeChecker<'interner> {
                 operator: crate::UnaryOp::Dereference { implicitly_added: true },
                 rhs: old_lhs,
             }));
-            this.interner.push_expr_type(&old_lhs, lhs_type);
-            this.interner.push_expr_type(access_lhs, element);
+            this.interner.push_expr_type(old_lhs, lhs_type);
+            this.interner.push_expr_type(*access_lhs, element);
 
             let old_location = this.interner.id_location(old_lhs);
             this.interner.push_expr_location(*access_lhs, span, old_location.file);
diff --git a/compiler/noirc_frontend/src/hir/type_check/mod.rs b/compiler/noirc_frontend/src/hir/type_check/mod.rs
index 4dcddbcca02..225f5756d7a 100644
--- a/compiler/noirc_frontend/src/hir/type_check/mod.rs
+++ b/compiler/noirc_frontend/src/hir/type_check/mod.rs
@@ -458,7 +458,7 @@ mod test {
         }
 
         fn local_module_id(&self) -> LocalModuleId {
-            LocalModuleId(arena::Index(0, generational_arena::Index::from_raw_parts(0, 0)))
+            LocalModuleId(arena::Index::unsafe_zeroed())
         }
 
         fn module_id(&self) -> ModuleId {
diff --git a/compiler/noirc_frontend/src/hir/type_check/stmt.rs b/compiler/noirc_frontend/src/hir/type_check/stmt.rs
index 03d61b93e0c..370b4ee7b17 100644
--- a/compiler/noirc_frontend/src/hir/type_check/stmt.rs
+++ b/compiler/noirc_frontend/src/hir/type_check/stmt.rs
@@ -192,7 +192,7 @@ impl<'interner> TypeChecker<'interner> {
                         mutable = definition.mutable;
                     }
 
-                    let typ = self.interner.id_type(ident.id).instantiate(self.interner).0;
+                    let typ = self.interner.definition_type(ident.id).instantiate(self.interner).0;
                     typ.follow_bindings()
                 };
 
diff --git a/compiler/noirc_frontend/src/hir_def/types.rs b/compiler/noirc_frontend/src/hir_def/types.rs
index 98b47f17cd4..d4d8a948460 100644
--- a/compiler/noirc_frontend/src/hir_def/types.rs
+++ b/compiler/noirc_frontend/src/hir_def/types.rs
@@ -1672,11 +1672,10 @@ fn convert_array_expression_to_slice(
     interner.push_expr_location(call, location.span, location.file);
     interner.push_expr_location(func, location.span, location.file);
 
-    interner.push_expr_type(&call, target_type.clone());
-    interner.push_expr_type(
-        &func,
-        Type::Function(vec![array_type], Box::new(target_type), Box::new(Type::Unit)),
-    );
+    interner.push_expr_type(call, target_type.clone());
+
+    let func_type = Type::Function(vec![array_type], Box::new(target_type), Box::new(Type::Unit));
+    interner.push_expr_type(func, func_type);
 }
 
 impl BinaryTypeOperator {
diff --git a/compiler/noirc_frontend/src/monomorphization/debug.rs b/compiler/noirc_frontend/src/monomorphization/debug.rs
index d36816e3d37..5837d67660a 100644
--- a/compiler/noirc_frontend/src/monomorphization/debug.rs
+++ b/compiler/noirc_frontend/src/monomorphization/debug.rs
@@ -143,7 +143,7 @@ impl<'interner> Monomorphizer<'interner> {
                     let index_id = self.interner.push_expr(HirExpression::Literal(
                         HirLiteral::Integer(field_index.into(), false),
                     ));
-                    self.interner.push_expr_type(&index_id, crate::Type::FieldElement);
+                    self.interner.push_expr_type(index_id, crate::Type::FieldElement);
                     self.interner.push_expr_location(
                         index_id,
                         call.location.span,
@@ -171,7 +171,7 @@ impl<'interner> Monomorphizer<'interner> {
     fn intern_var_id(&mut self, var_id: DebugVarId, location: &Location) -> ExprId {
         let var_id_literal = HirLiteral::Integer((var_id.0 as u128).into(), false);
         let expr_id = self.interner.push_expr(HirExpression::Literal(var_id_literal));
-        self.interner.push_expr_type(&expr_id, crate::Type::FieldElement);
+        self.interner.push_expr_type(expr_id, crate::Type::FieldElement);
         self.interner.push_expr_location(expr_id, location.span, location.file);
         expr_id
     }
diff --git a/compiler/noirc_frontend/src/monomorphization/mod.rs b/compiler/noirc_frontend/src/monomorphization/mod.rs
index f691a0c9065..3f255bf6d0a 100644
--- a/compiler/noirc_frontend/src/monomorphization/mod.rs
+++ b/compiler/noirc_frontend/src/monomorphization/mod.rs
@@ -696,7 +696,7 @@ impl<'interner> Monomorphizer<'interner> {
         let mutable = definition.mutable;
 
         let definition = self.lookup_local(ident.id)?;
-        let typ = self.convert_type(&self.interner.id_type(ident.id));
+        let typ = self.convert_type(&self.interner.definition_type(ident.id));
 
         Some(ast::Ident { location: Some(ident.location), mutable, definition, name, typ })
     }
@@ -1038,7 +1038,7 @@ impl<'interner> Monomorphizer<'interner> {
     ) {
         match hir_argument {
             HirExpression::Ident(ident) => {
-                let typ = self.interner.id_type(ident.id);
+                let typ = self.interner.definition_type(ident.id);
                 let typ: Type = typ.follow_bindings();
                 let is_fmt_str = match typ {
                     // A format string has many different possible types that need to be handled.
diff --git a/compiler/noirc_frontend/src/node_interner.rs b/compiler/noirc_frontend/src/node_interner.rs
index 42584ce0265..f0a006489f4 100644
--- a/compiler/noirc_frontend/src/node_interner.rs
+++ b/compiler/noirc_frontend/src/node_interner.rs
@@ -75,13 +75,14 @@ pub struct NodeInterner {
 
     // Type checking map
     //
-    // Notice that we use `Index` as the Key and not an ExprId or IdentId
-    // Therefore, If a raw index is passed in, then it is not safe to assume that it will have
-    // a Type, as not all Ids have types associated to them.
-    // Further note, that an ExprId and an IdentId will never have the same underlying Index
-    // Because we use one Arena to store all Definitions/Nodes
+    // This should only be used with indices from the `nodes` arena.
+    // Otherwise the indices used may overwrite other existing indices.
+    // Each type for each index is filled in during type checking.
     id_to_type: HashMap<Index, Type>,
 
+    // Similar to `id_to_type` but maps definitions to their type
+    definition_to_type: HashMap<DefinitionId, Type>,
+
     // Struct map.
     //
     // Each struct definition is possibly shared across multiple type nodes.
@@ -277,12 +278,6 @@ impl DefinitionId {
     }
 }
 
-impl From<DefinitionId> for Index {
-    fn from(id: DefinitionId) -> Self {
-        Index(id.0)
-    }
-}
-
 /// An ID for a global value
 #[derive(Debug, Eq, PartialEq, Hash, Clone, Copy)]
 pub struct GlobalId(usize);
@@ -302,7 +297,7 @@ impl StmtId {
     // This can be anything, as the program will ultimately fail
     // after resolution
     pub fn dummy_id() -> StmtId {
-        StmtId(Index(std::usize::MAX))
+        StmtId(Index::dummy())
     }
 }
 
@@ -311,7 +306,7 @@ pub struct ExprId(Index);
 
 impl ExprId {
     pub fn empty_block_id() -> ExprId {
-        ExprId(Index(0))
+        ExprId(Index::unsafe_zeroed())
     }
 }
 #[derive(Debug, Eq, PartialEq, Hash, Copy, Clone)]
@@ -322,7 +317,7 @@ impl FuncId {
     // This can be anything, as the program will ultimately fail
     // after resolution
     pub fn dummy_id() -> FuncId {
-        FuncId(Index(std::usize::MAX))
+        FuncId(Index::dummy())
     }
 }
 
@@ -396,23 +391,9 @@ macro_rules! into_index {
     };
 }
 
-macro_rules! partialeq {
-    ($id_type:ty) => {
-        impl PartialEq<usize> for &$id_type {
-            fn eq(&self, other: &usize) -> bool {
-                let index = self.0 .0;
-                index == *other
-            }
-        }
-    };
-}
-
 into_index!(ExprId);
 into_index!(StmtId);
 
-partialeq!(ExprId);
-partialeq!(StmtId);
-
 /// A Definition enum specifies anything that we can intern in the NodeInterner
 /// We use one Arena for all types that can be interned as that has better cache locality
 /// This data structure is never accessed directly, so API wise there is no difference between using
@@ -496,6 +477,7 @@ impl Default for NodeInterner {
             id_to_location: HashMap::new(),
             definitions: vec![],
             id_to_type: HashMap::new(),
+            definition_to_type: HashMap::new(),
             structs: HashMap::new(),
             struct_attributes: HashMap::new(),
             type_aliases: Vec::new(),
@@ -545,10 +527,15 @@ impl NodeInterner {
     }
 
     /// Store the type for an interned expression
-    pub fn push_expr_type(&mut self, expr_id: &ExprId, typ: Type) {
+    pub fn push_expr_type(&mut self, expr_id: ExprId, typ: Type) {
         self.id_to_type.insert(expr_id.into(), typ);
     }
 
+    /// Store the type for an interned expression
+    pub fn push_definition_type(&mut self, definition_id: DefinitionId, typ: Type) {
+        self.definition_to_type.insert(definition_id, typ);
+    }
+
     pub fn push_empty_trait(&mut self, type_id: TraitId, unresolved_trait: &UnresolvedTrait) {
         let self_type_typevar_id = self.next_type_variable_id();
 
@@ -660,11 +647,6 @@ impl NodeInterner {
         }
     }
 
-    /// Store the type for an interned Identifier
-    pub fn push_definition_type(&mut self, definition_id: DefinitionId, typ: Type) {
-        self.id_to_type.insert(definition_id.into(), typ);
-    }
-
     /// Store [Location] of [Type] reference
     pub fn push_type_ref_location(&mut self, typ: Type, location: Location) {
         self.type_ref_locations.push((typ, location));
@@ -980,8 +962,13 @@ impl NodeInterner {
         self.id_to_type.get(&index.into()).cloned().unwrap_or(Type::Error)
     }
 
+    /// Returns the type of the definition or `Type::Error` if it was not found.
+    pub fn definition_type(&self, id: DefinitionId) -> Type {
+        self.definition_to_type.get(&id).cloned().unwrap_or(Type::Error)
+    }
+
     pub fn id_type_substitute_trait_as_type(&self, def_id: DefinitionId) -> Type {
-        let typ = self.id_type(def_id);
+        let typ = self.definition_type(def_id);
         if let Type::Function(args, ret, env) = &typ {
             let def = self.definition(def_id);
             if let Type::TraitAsType(..) = ret.as_ref() {
diff --git a/compiler/utils/arena/src/lib.rs b/compiler/utils/arena/src/lib.rs
index cf834ed7d59..ec9b1d9a837 100644
--- a/compiler/utils/arena/src/lib.rs
+++ b/compiler/utils/arena/src/lib.rs
@@ -4,7 +4,26 @@
 #![warn(clippy::semicolon_if_nothing_returned)]
 
 #[derive(Clone, Copy, Debug, Eq, Ord, PartialEq, PartialOrd, Hash)]
-pub struct Index(pub usize);
+pub struct Index(usize);
+
+impl Index {
+    #[cfg(test)]
+    pub fn test_new(index: usize) -> Index {
+        Self(index)
+    }
+
+    /// Return a dummy index (max value internally).
+    /// This should be avoided over `Option<Index>` if possible.
+    pub fn dummy() -> Self {
+        Self(usize::MAX)
+    }
+
+    /// Return the zeroed index. This is unsafe since we don't know
+    /// if this is a valid index for any particular map yet.
+    pub fn unsafe_zeroed() -> Self {
+        Self(0)
+    }
+}
 
 // #[derive(Debug, Eq, PartialEq, Hash, Clone)]
 #[derive(Debug, Clone)]

From 7885574494cc3ecc058eac0f5a0cc2ead123a54d Mon Sep 17 00:00:00 2001
From: "Michael J. Klein" <lambdamichael@gmail.com>
Date: Fri, 16 Feb 2024 14:28:56 -0500
Subject: [PATCH 16/16] cleanup debugging, remove generational arena note from
 deny.toml

---
 .../src/hir/def_map/item_scope.rs             |  2 +-
 .../src/hir/def_map/module_data.rs            |  2 +-
 compiler/noirc_frontend/src/hir_def/expr.rs   | 30 +++++++++----------
 .../noirc_frontend/src/hir_def/function.rs    |  2 +-
 compiler/noirc_frontend/src/hir_def/stmt.rs   | 12 ++++----
 compiler/noirc_frontend/src/node_interner.rs  |  2 +-
 compiler/utils/arena/src/lib.rs               | 11 ++-----
 deny.toml                                     |  2 +-
 8 files changed, 29 insertions(+), 34 deletions(-)

diff --git a/compiler/noirc_frontend/src/hir/def_map/item_scope.rs b/compiler/noirc_frontend/src/hir/def_map/item_scope.rs
index 50f1f50cbe5..523def89518 100644
--- a/compiler/noirc_frontend/src/hir/def_map/item_scope.rs
+++ b/compiler/noirc_frontend/src/hir/def_map/item_scope.rs
@@ -12,7 +12,7 @@ pub enum Visibility {
     Public,
 }
 
-#[derive(Clone, Default, Debug, PartialEq, Eq)]
+#[derive(Default, Debug, PartialEq, Eq)]
 pub struct ItemScope {
     types: HashMap<Ident, Scope>,
     values: HashMap<Ident, Scope>,
diff --git a/compiler/noirc_frontend/src/hir/def_map/module_data.rs b/compiler/noirc_frontend/src/hir/def_map/module_data.rs
index 6284cf252c1..309618dd011 100644
--- a/compiler/noirc_frontend/src/hir/def_map/module_data.rs
+++ b/compiler/noirc_frontend/src/hir/def_map/module_data.rs
@@ -11,7 +11,7 @@ use super::{ItemScope, LocalModuleId, ModuleDefId, ModuleId, PerNs};
 
 /// Contains the actual contents of a module: its parent (if one exists),
 /// children, and scope with all definitions defined within the scope.
-#[derive(Clone, Debug, PartialEq, Eq)]
+#[derive(Debug, PartialEq, Eq)]
 pub struct ModuleData {
     pub parent: Option<LocalModuleId>,
     pub children: HashMap<Ident, LocalModuleId>,
diff --git a/compiler/noirc_frontend/src/hir_def/expr.rs b/compiler/noirc_frontend/src/hir_def/expr.rs
index 70f53a24532..75ed68af0f6 100644
--- a/compiler/noirc_frontend/src/hir_def/expr.rs
+++ b/compiler/noirc_frontend/src/hir_def/expr.rs
@@ -14,7 +14,7 @@ use super::types::{StructType, Type};
 /// references other HIR nodes indirectly via IDs rather than directly via
 /// boxing. Variables in HirExpressions are tagged with their DefinitionId
 /// from the definition that refers to them so there is no ambiguity with names.
-#[derive(Debug, Clone, PartialEq)]
+#[derive(Debug, Clone)]
 pub enum HirExpression {
     Ident(HirIdent),
     Literal(HirLiteral),
@@ -109,7 +109,7 @@ impl HirBinaryOp {
     }
 }
 
-#[derive(Debug, Clone, PartialEq)]
+#[derive(Debug, Clone)]
 pub enum HirLiteral {
     Array(HirArrayLiteral),
     Bool(bool),
@@ -119,19 +119,19 @@ pub enum HirLiteral {
     Unit,
 }
 
-#[derive(Debug, Clone, PartialEq)]
+#[derive(Debug, Clone)]
 pub enum HirArrayLiteral {
     Standard(Vec<ExprId>),
     Repeated { repeated_element: ExprId, length: Type },
 }
 
-#[derive(Debug, Clone, PartialEq)]
+#[derive(Debug, Clone)]
 pub struct HirPrefixExpression {
     pub operator: UnaryOp,
     pub rhs: ExprId,
 }
 
-#[derive(Debug, Clone, PartialEq)]
+#[derive(Debug, Clone)]
 pub struct HirInfixExpression {
     pub lhs: ExprId,
     pub operator: HirBinaryOp,
@@ -146,7 +146,7 @@ pub struct HirInfixExpression {
 
 /// This is always a struct field access `my_struct.field`
 /// and never a method call. The later is represented by HirMethodCallExpression.
-#[derive(Debug, Clone, PartialEq)]
+#[derive(Debug, Clone)]
 pub struct HirMemberAccess {
     pub lhs: ExprId,
     // This field is not an IdentId since the rhs of a field
@@ -160,7 +160,7 @@ pub struct HirMemberAccess {
     pub is_offset: bool,
 }
 
-#[derive(Debug, Clone, PartialEq)]
+#[derive(Debug, Clone)]
 pub struct HirIfExpression {
     pub condition: ExprId,
     pub consequence: ExprId,
@@ -168,13 +168,13 @@ pub struct HirIfExpression {
 }
 
 // `lhs as type` in the source code
-#[derive(Debug, Clone, PartialEq)]
+#[derive(Debug, Clone)]
 pub struct HirCastExpression {
     pub lhs: ExprId,
     pub r#type: Type,
 }
 
-#[derive(Debug, Clone, PartialEq)]
+#[derive(Debug, Clone)]
 pub struct HirCallExpression {
     pub func: ExprId,
     pub arguments: Vec<ExprId>,
@@ -185,7 +185,7 @@ pub struct HirCallExpression {
 /// lowered into HirCallExpression nodes
 /// after type checking resolves the object
 /// type and the method it calls.
-#[derive(Debug, Clone, PartialEq)]
+#[derive(Debug, Clone)]
 pub struct HirMethodCallExpression {
     pub method: Ident,
     pub object: ExprId,
@@ -239,7 +239,7 @@ impl HirMethodCallExpression {
     }
 }
 
-#[derive(Debug, Clone, PartialEq)]
+#[derive(Debug, Clone)]
 pub struct HirConstructorExpression {
     pub r#type: Shared<StructType>,
     pub struct_generics: Vec<Type>,
@@ -253,13 +253,13 @@ pub struct HirConstructorExpression {
 }
 
 /// Indexing, as in `array[index]`
-#[derive(Debug, Clone, PartialEq)]
+#[derive(Debug, Clone)]
 pub struct HirIndexExpression {
     pub collection: ExprId,
     pub index: ExprId,
 }
 
-#[derive(Debug, Clone, PartialEq)]
+#[derive(Debug, Clone)]
 pub struct HirBlockExpression(pub Vec<StmtId>);
 
 impl HirBlockExpression {
@@ -269,7 +269,7 @@ impl HirBlockExpression {
 }
 
 /// A variable captured inside a closure
-#[derive(Debug, Clone, PartialEq)]
+#[derive(Debug, Clone)]
 pub struct HirCapturedVar {
     pub ident: HirIdent,
 
@@ -283,7 +283,7 @@ pub struct HirCapturedVar {
     pub transitive_capture_index: Option<usize>,
 }
 
-#[derive(Debug, Clone, PartialEq)]
+#[derive(Debug, Clone)]
 pub struct HirLambda {
     pub parameters: Vec<(HirPattern, Type)>,
     pub return_type: Type,
diff --git a/compiler/noirc_frontend/src/hir_def/function.rs b/compiler/noirc_frontend/src/hir_def/function.rs
index 0b0365a66f6..d3ab2a9393b 100644
--- a/compiler/noirc_frontend/src/hir_def/function.rs
+++ b/compiler/noirc_frontend/src/hir_def/function.rs
@@ -10,7 +10,7 @@ use crate::{Distinctness, FunctionReturnType, Type, Visibility};
 
 /// A Hir function is a block expression
 /// with a list of statements
-#[derive(Debug, Clone, PartialEq)]
+#[derive(Debug, Clone)]
 pub struct HirFunction(ExprId);
 
 impl HirFunction {
diff --git a/compiler/noirc_frontend/src/hir_def/stmt.rs b/compiler/noirc_frontend/src/hir_def/stmt.rs
index fbca33c4912..b910be1fdda 100644
--- a/compiler/noirc_frontend/src/hir_def/stmt.rs
+++ b/compiler/noirc_frontend/src/hir_def/stmt.rs
@@ -8,7 +8,7 @@ use noirc_errors::{Location, Span};
 /// the Statement AST node. Unlike the AST node, any nested nodes
 /// are referred to indirectly via ExprId or StmtId, which can be
 /// used to retrieve the relevant node via the NodeInterner.
-#[derive(Debug, Clone, PartialEq)]
+#[derive(Debug, Clone)]
 pub enum HirStatement {
     Let(HirLetStatement),
     Constrain(HirConstrainStatement),
@@ -19,7 +19,7 @@ pub enum HirStatement {
     Error,
 }
 
-#[derive(Debug, Clone, PartialEq)]
+#[derive(Debug, Clone)]
 pub struct HirLetStatement {
     pub pattern: HirPattern,
     pub r#type: Type,
@@ -35,7 +35,7 @@ impl HirLetStatement {
     }
 }
 
-#[derive(Debug, Clone, PartialEq)]
+#[derive(Debug, Clone)]
 pub struct HirForStatement {
     pub identifier: HirIdent,
     pub start_range: ExprId,
@@ -44,7 +44,7 @@ pub struct HirForStatement {
 }
 
 /// Corresponds to `lvalue = expression;` in the source code
-#[derive(Debug, Clone, PartialEq)]
+#[derive(Debug, Clone)]
 pub struct HirAssignStatement {
     pub lvalue: HirLValue,
     pub expression: ExprId,
@@ -54,10 +54,10 @@ pub struct HirAssignStatement {
 /// This node also contains the FileId of the file the constrain
 /// originates from. This is used later in the SSA pass to issue
 /// an error if a constrain is found to be always false.
-#[derive(Debug, Clone, PartialEq)]
+#[derive(Debug, Clone)]
 pub struct HirConstrainStatement(pub ExprId, pub FileId, pub Option<ExprId>);
 
-#[derive(Debug, Clone, Hash, PartialEq)]
+#[derive(Debug, Clone, Hash)]
 pub enum HirPattern {
     Identifier(HirIdent),
     Mutable(Box<HirPattern>, Location),
diff --git a/compiler/noirc_frontend/src/node_interner.rs b/compiler/noirc_frontend/src/node_interner.rs
index f0a006489f4..a791112926e 100644
--- a/compiler/noirc_frontend/src/node_interner.rs
+++ b/compiler/noirc_frontend/src/node_interner.rs
@@ -398,7 +398,7 @@ into_index!(StmtId);
 /// We use one Arena for all types that can be interned as that has better cache locality
 /// This data structure is never accessed directly, so API wise there is no difference between using
 /// Multiple arenas and a single Arena
-#[derive(Debug, Clone, PartialEq)]
+#[derive(Debug, Clone)]
 pub(crate) enum Node {
     Function(HirFunction),
     Statement(HirStatement),
diff --git a/compiler/utils/arena/src/lib.rs b/compiler/utils/arena/src/lib.rs
index ec9b1d9a837..2d117304e16 100644
--- a/compiler/utils/arena/src/lib.rs
+++ b/compiler/utils/arena/src/lib.rs
@@ -25,8 +25,7 @@ impl Index {
     }
 }
 
-// #[derive(Debug, Eq, PartialEq, Hash, Clone)]
-#[derive(Debug, Clone)]
+#[derive(Clone, Debug)]
 pub struct Arena<T> {
     pub vec: Vec<T>,
 }
@@ -71,14 +70,10 @@ impl<'a, T> IntoIterator for &'a Arena<T> {
     }
 }
 
-// TODO: remove Clone
 impl<T> Arena<T> {
-    pub fn insert(&mut self, item: T) -> Index
-    where
-        T: Clone,
-    {
+    pub fn insert(&mut self, item: T) -> Index {
         let index = self.vec.len();
-        self.vec.push(item.clone());
+        self.vec.push(item);
         Index(index)
     }
 
diff --git a/deny.toml b/deny.toml
index a3e506984c9..72150f08a3c 100644
--- a/deny.toml
+++ b/deny.toml
@@ -54,7 +54,7 @@ allow = [
     "LicenseRef-ring",
     # https://github.com/rustls/webpki/blob/main/LICENSE ISC Style
     "LicenseRef-rustls-webpki",
-    # bitmaps 2.1.0, generational-arena 0.2.9,im 15.1.0
+    # bitmaps 2.1.0, im 15.1.0
     "MPL-2.0",
     # Boost Software License
     "BSL-1.0",