refactor: make Note a marker trait

Author: olehmisar

packages/contracts/noir/common/src/erc20_note.nr

@@ -1,5 +1,3 @@
-use protocol_types::hash::poseidon2_hash_with_separator;
-
 // fails to compile if this file is moved to erc20 crate
 
 pub struct Erc20Note {
@@ -8,6 +6,8 @@ pub struct Erc20Note {
     pub randomness: Field,
 }
 
+impl crate::Note for Erc20Note {}
+
 impl Erc20Note {
     pub fn sub_and_emit_change<let N: u32>(
         context: &mut crate::Context,
@@ -41,13 +41,6 @@ impl crate::Serialize<6> for Erc20Note {
     }
 }
 
-impl crate::Note for Erc20Note {
-    fn hash(self) -> Field {
-        let serialized = self.serialize();
-        poseidon2_hash_with_separator(serialized, crate::GENERATOR_INDEX__NOTE_HASH)
-    }
-}
-
 impl crate::OwnedNote for Erc20Note {
     fn owner(self) -> crate::WaAddress {
         self.owner

packages/contracts/noir/common/src/lib.nr

@@ -7,8 +7,7 @@ mod note;
 mod owned_note;
 
 pub use context::{Context, Result};
-pub use erc20_note::{Erc20Note, Erc20NoteConsumptionInputs};
-pub use note::Note;
+pub use note::{compute_note_hash, Note};
 pub use owned_note::{NoteConsumptionInputs, OwnedNote};
 pub use protocol_types::{address::EthAddress, traits::Serialize};
 

packages/contracts/noir/common/src/note.nr

@@ -1,7 +1,18 @@
-pub trait Note {
-    fn hash(self) -> Field;
+use protocol_types::hash::poseidon2_hash_with_separator;
+
+/// A marker trait to mark structs as notes
+pub trait Note: crate::Serialize<_> {
 
     pub fn emit(self, context: &mut crate::Context) {
-        context.push_note_hash(self.hash());
+        context.push_note_hash(crate::compute_note_hash(self));
     }
 }
+
+pub fn compute_note_hash<T>(note: T) -> Field
+where
+    T: Note,
+{
+    let serialized = note.serialize();
+    // TODO(security): add note type to the hash (erc20, erc721, etc.)
+    poseidon2_hash_with_separator(serialized, crate::GENERATOR_INDEX__NOTE_HASH)
+}

packages/contracts/noir/common/src/owned_note.nr

@@ -11,9 +11,10 @@ fn compute_nullifier_of_owned_note<T>(note: T, secret_key: Field) -> Field
 where
     T: OwnedNote,
 {
+    // TODO(perf): pass note hash as an argument to avoid hashing twice?
     assert_eq(note.owner(), crate::WaAddress::from_secret_key(secret_key), "invalid secret key");
     poseidon2_hash_with_separator(
-        [note.hash(), secret_key],
+        [crate::compute_note_hash(note), secret_key],
         crate::GENERATOR_INDEX__NOTE_NULLIFIER,
     )
 }
@@ -32,7 +33,7 @@ where
 {
     pub fn consume(self, context: &mut crate::Context, secret_key: Field) {
         merkle_tree::assert_check_membership(
-            self.note.hash(),
+            crate::compute_note_hash(self.note),
             self.note_index,
             self.note_sibling_path,
             context.tree_roots().note_hash_root,

packages/contracts/noir/erc20/src/lib.nr

@@ -1,4 +1,4 @@
-pub use common::{Erc20Note, Erc20NoteConsumptionInputs};
+pub use common::erc20_note::{Erc20Note, Erc20NoteConsumptionInputs};
 
 pub mod Token {
     pub fn mint(
@@ -7,17 +7,17 @@ pub mod Token {
         amount: common::TokenAmount,
         randomness: Field,
     ) {
-        common::Erc20Note { owner: to, amount, randomness }.emit(context);
+        crate::Erc20Note { owner: to, amount, randomness }.emit(context);
     }
 
     pub fn burn(
         context: &mut common::Context,
         from_secret_key: Field,
-        from_note_inputs: common::Erc20NoteConsumptionInputs,
+        from_note_inputs: crate::Erc20NoteConsumptionInputs,
         amount: common::TokenAmount,
         change_randomness: Field,
     ) {
-        common::Erc20Note::sub_and_emit_change(
+        crate::Erc20Note::sub_and_emit_change(
             context,
             [from_note_inputs],
             amount,
@@ -29,7 +29,7 @@ pub mod Token {
     pub fn join<let N: u32>(
         context: &mut common::Context,
         from_secret_key: Field,
-        notes: [common::Erc20NoteConsumptionInputs; N],
+        notes: [crate::Erc20NoteConsumptionInputs; N],
         to: common::WaAddress,
         join_randomness: Field,
     ) {
@@ -42,27 +42,27 @@ pub mod Token {
             joined_amount += notes[i].note.amount;
         }
 
-        common::Erc20Note { owner: to, amount: joined_amount, randomness: join_randomness }.emit(
+        crate::Erc20Note { owner: to, amount: joined_amount, randomness: join_randomness }.emit(
             context,
         );
     }
 
     pub fn transfer(
         context: &mut common::Context,
         from_secret_key: Field,
-        from_note_inputs: common::Erc20NoteConsumptionInputs,
+        from_note_inputs: crate::Erc20NoteConsumptionInputs,
         to: common::WaAddress,
         amount: common::TokenAmount,
         to_randomness: Field,
         change_randomness: Field,
     ) {
-        common::Erc20Note::sub_and_emit_change(
+        crate::Erc20Note::sub_and_emit_change(
             context,
             [from_note_inputs],
             amount,
             change_randomness,
             from_secret_key,
         );
-        common::Erc20Note { owner: to, amount, randomness: to_randomness }.emit(context);
+        crate::Erc20Note { owner: to, amount, randomness: to_randomness }.emit(context);
     }
 }

packages/contracts/noir/erc20_join/src/main.nr

@@ -5,7 +5,7 @@ fn main(
     tree_roots: pub common::TreeRoots,
     // params
     from_secret_key: Field,
-    notes: [common::Erc20NoteConsumptionInputs; MAX_NOTES_TO_JOIN],
+    notes: [erc20::Erc20NoteConsumptionInputs; MAX_NOTES_TO_JOIN],
     to: common::WaAddress,
     join_randomness: Field,
 ) -> pub common::Result<1, MAX_NOTES_TO_JOIN> {