Ops id trait (#1758)

### Description to address discussion in PR #1748 ### Rationale implement OpsIdentity for word<T> so that we no longer need to type hint `::<Expression<F>>` or `::<F>` every time.
privacy-scaling-explorations · Feb 6, 2024 · be9fed5 · be9fed5
1 parent 81e715a
commit be9fed5
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diff --git a/eth-types/src/lib.rs b/eth-types/src/lib.rs
@@ -24,9 +24,12 @@ pub use keccak::{keccak256, Keccak};
 
 pub use bytecode::Bytecode;
 pub use error::Error;
-use halo2_proofs::halo2curves::{
-    bn256::{Fq, Fr},
-    ff::{Field as Halo2Field, FromUniformBytes, PrimeField},
+use halo2_proofs::{
+    halo2curves::{
+        bn256::{Fq, Fr},
+        ff::{Field as Halo2Field, FromUniformBytes, PrimeField},
+    },
+    plonk::Expression,
 };
 
 use crate::evm_types::{memory::Memory, stack::Stack, storage::Storage, OpcodeId};
@@ -42,9 +45,58 @@ pub use ethers_core::{
 use serde::{de, Deserialize, Serialize};
 use std::{collections::HashMap, fmt, str::FromStr};
 
+/// trait to retrieve general operation itentity element
+pub trait OpsIdentity {
+    /// output type
+    type Output;
+    /// additive identity
+    fn zero() -> Self::Output;
+    /// multiplicative identity
+    fn one() -> Self::Output;
+}
+
+impl<F: Field> OpsIdentity for Expression<F> {
+    type Output = Expression<F>;
+    fn zero() -> Self::Output {
+        Expression::Constant(F::ZERO)
+    }
+
+    fn one() -> Self::Output {
+        Expression::Constant(F::ONE)
+    }
+}
+
+// Impl OpsIdentity for Fr
+impl OpsIdentity for Fr {
+    type Output = Fr;
+
+    fn zero() -> Self::Output {
+        Fr::zero()
+    }
+
+    fn one() -> Self::Output {
+        Fr::one()
+    }
+}
+
+// Impl OpsIdentity for Fq
+impl OpsIdentity for Fq {
+    type Output = Fq;
+
+    fn zero() -> Self::Output {
+        Fq::zero()
+    }
+
+    fn one() -> Self::Output {
+        Fq::one()
+    }
+}
+
 /// Trait used to reduce verbosity with the declaration of the [`PrimeField`]
 /// trait and its repr.
-pub trait Field: Halo2Field + PrimeField<Repr = [u8; 32]> + FromUniformBytes<64> + Ord {
+pub trait Field:
+    Halo2Field + PrimeField<Repr = [u8; 32]> + FromUniformBytes<64> + Ord + OpsIdentity<Output = Self>
+{
     /// Gets the lower 128 bits of this field element when expressed
     /// canonically.
     fn get_lower_128(&self) -> u128 {

diff --git a/zkevm-circuits/src/evm_circuit/execution/begin_tx.rs b/zkevm-circuits/src/evm_circuit/execution/begin_tx.rs
@@ -27,7 +27,7 @@ use crate::{
     },
 };
 use bus_mapping::state_db::CodeDB;
-use eth_types::{evm_types::PRECOMPILE_COUNT, keccak256, Field, ToWord, U256};
+use eth_types::{evm_types::PRECOMPILE_COUNT, keccak256, Field, OpsIdentity, ToWord, U256};
 use halo2_proofs::{
     circuit::Value,
     plonk::{Error, Expression},

diff --git a/zkevm-circuits/src/evm_circuit/execution/callop.rs b/zkevm-circuits/src/evm_circuit/execution/callop.rs
@@ -31,7 +31,9 @@ use bus_mapping::{
     evm::OpcodeId,
     precompile::{is_precompiled, PrecompileCalls},
 };
-use eth_types::{evm_types::GAS_STIPEND_CALL_WITH_VALUE, Field, ToAddress, ToScalar, U256};
+use eth_types::{
+    evm_types::GAS_STIPEND_CALL_WITH_VALUE, Field, OpsIdentity, ToAddress, ToScalar, U256,
+};
 use halo2_proofs::{circuit::Value, plonk::Error};
 use std::cmp::min;
 

diff --git a/zkevm-circuits/src/evm_circuit/execution/create.rs b/zkevm-circuits/src/evm_circuit/execution/create.rs
@@ -34,7 +34,7 @@ use bus_mapping::{
 };
 use eth_types::{
     evm_types::{GasCost, INIT_CODE_WORD_GAS},
-    Field, ToBigEndian, ToScalar, ToWord, U256,
+    Field, OpsIdentity, ToBigEndian, ToScalar, ToWord, U256,
 };
 use ethers_core::utils::keccak256;
 use gadgets::util::{and, select};

diff --git a/zkevm-circuits/src/evm_circuit/execution/end_block.rs b/zkevm-circuits/src/evm_circuit/execution/end_block.rs
@@ -14,7 +14,7 @@ use crate::{
     table::{CallContextFieldTag, TxContextFieldTag},
     util::{word::Word, Expr},
 };
-use eth_types::Field;
+use eth_types::{Field, OpsIdentity};
 use gadgets::util::select;
 use halo2_proofs::{circuit::Value, plonk::Error};
 

diff --git a/zkevm-circuits/src/evm_circuit/execution/error_precompile_failed.rs b/zkevm-circuits/src/evm_circuit/execution/error_precompile_failed.rs
@@ -17,7 +17,7 @@ use crate::{
     witness::{Block, Call, ExecStep, Transaction},
 };
 use bus_mapping::evm::OpcodeId;
-use eth_types::{Field, U256};
+use eth_types::{Field, OpsIdentity, U256};
 use halo2_proofs::{circuit::Value, plonk::Error};
 
 #[derive(Clone, Debug)]

diff --git a/zkevm-circuits/src/evm_circuit/execution/error_write_protection.rs b/zkevm-circuits/src/evm_circuit/execution/error_write_protection.rs
@@ -16,7 +16,7 @@ use crate::{
         Expr,
     },
 };
-use eth_types::{evm_types::OpcodeId, Field, ToAddress, U256};
+use eth_types::{evm_types::OpcodeId, Field, OpsIdentity, ToAddress, U256};
 use halo2_proofs::{circuit::Value, plonk::Error};
 
 #[derive(Clone, Debug)]

diff --git a/zkevm-circuits/src/evm_circuit/execution/stop.rs b/zkevm-circuits/src/evm_circuit/execution/stop.rs
@@ -21,7 +21,7 @@ use crate::{
     },
 };
 use bus_mapping::evm::OpcodeId;
-use eth_types::Field;
+use eth_types::{Field, OpsIdentity};
 use halo2_proofs::{circuit::Value, plonk::Error};
 
 #[derive(Clone, Debug)]

diff --git a/zkevm-circuits/src/evm_circuit/util/common_gadget.rs b/zkevm-circuits/src/evm_circuit/util/common_gadget.rs
@@ -28,7 +28,9 @@ use crate::{
     witness::{Block, Call, ExecStep},
 };
 use bus_mapping::state_db::CodeDB;
-use eth_types::{evm_types::GasCost, Field, ToAddress, ToLittleEndian, ToScalar, ToWord, U256};
+use eth_types::{
+    evm_types::GasCost, Field, OpsIdentity, ToAddress, ToLittleEndian, ToScalar, ToWord, U256,
+};
 use gadgets::util::{select, sum};
 use halo2_proofs::{
     circuit::Value,

diff --git a/zkevm-circuits/src/evm_circuit/util/constraint_builder.rs b/zkevm-circuits/src/evm_circuit/util/constraint_builder.rs
@@ -18,7 +18,7 @@ use crate::{
 use bus_mapping::{
     circuit_input_builder::FeatureConfig, operation::Target, state_db::EMPTY_CODE_HASH_LE,
 };
-use eth_types::Field;
+use eth_types::{Field, OpsIdentity};
 use gadgets::util::{not, sum};
 use halo2_proofs::{
     circuit::Value,

diff --git a/zkevm-circuits/src/mpt_circuit/account_leaf.rs b/zkevm-circuits/src/mpt_circuit/account_leaf.rs
@@ -1,4 +1,4 @@
-use eth_types::{Field, U256};
+use eth_types::{Field, OpsIdentity, U256};
 use gadgets::util::{pow, Scalar};
 use halo2_proofs::{
     circuit::Value,
@@ -554,10 +554,10 @@ impl<F: Field> AccountLeafConfig<F> {
 
         // Key
         let mut key_rlc = vec![0.scalar(); 2];
-        let mut nonce = vec![Word::zero_f(); 2];
-        let mut balance = vec![Word::zero_f(); 2];
-        let mut storage = vec![Word::zero_f(); 2];
-        let mut codehash = vec![Word::zero_f(); 2];
+        let mut nonce = vec![Word::zero(); 2];
+        let mut balance = vec![Word::zero(); 2];
+        let mut storage = vec![Word::zero(); 2];
+        let mut codehash = vec![Word::zero(); 2];
         let mut key_data = vec![KeyDataWitness::default(); 2];
         let mut parent_data = vec![ParentDataWitness::default(); 2];
         for is_s in [true, false] {
@@ -727,11 +727,11 @@ impl<F: Field> AccountLeafConfig<F> {
         } else if is_codehash_mod {
             (MPTProofType::CodeHashChanged, codehash)
         } else if is_account_delete_mod {
-            (MPTProofType::AccountDestructed, vec![Word::zero_f(); 2])
+            (MPTProofType::AccountDestructed, vec![Word::zero(); 2])
         } else if is_non_existing_proof {
-            (MPTProofType::AccountDoesNotExist, vec![Word::zero_f(); 2])
+            (MPTProofType::AccountDoesNotExist, vec![Word::zero(); 2])
         } else {
-            (MPTProofType::Disabled, vec![Word::zero_f(); 2])
+            (MPTProofType::Disabled, vec![Word::zero(); 2])
         };
 
         if account.is_mod_extension[0] || account.is_mod_extension[1] {
@@ -746,10 +746,10 @@ impl<F: Field> AccountLeafConfig<F> {
         let mut new_value = value[false.idx()];
         let mut old_value = value[true.idx()];
         if parent_data[false.idx()].is_placeholder {
-            new_value = word::Word::zero_f();
+            new_value = word::Word::zero();
         } else if is_non_existing_proof {
-            new_value = word::Word::zero_f();
-            old_value = word::Word::zero_f();
+            new_value = word::Word::zero();
+            old_value = word::Word::zero();
         }
         mpt_config.mpt_table.assign_cached(
             region,
@@ -758,7 +758,7 @@ impl<F: Field> AccountLeafConfig<F> {
                 address: Value::known(from_bytes::value(
                     &account.address.iter().cloned().rev().collect::<Vec<_>>(),
                 )),
-                storage_key: word::Word::zero_f().into_value(),
+                storage_key: word::Word::zero().into_value(),
                 proof_type: Value::known(proof_type.scalar()),
                 new_root: main_data.new_root.into_value(),
                 old_root: main_data.old_root.into_value(),

diff --git a/zkevm-circuits/src/mpt_circuit/branch.rs b/zkevm-circuits/src/mpt_circuit/branch.rs
@@ -1,4 +1,4 @@
-use eth_types::Field;
+use eth_types::{Field, OpsIdentity};
 use gadgets::util::Scalar;
 use halo2_proofs::plonk::{Error, Expression, VirtualCells};
 
@@ -351,7 +351,7 @@ impl<F: Field> BranchGadget<F> {
         let key_mult_post_branch = *key_mult * mult;
 
         // Set the branch we'll take
-        let mut mod_node_hash_word = [word::Word::zero_f(); 2];
+        let mut mod_node_hash_word = [word::Word::zero(); 2];
         let mut mod_node_hash_rlc = [0.scalar(); 2];
         for is_s in [true, false] {
             (

diff --git a/zkevm-circuits/src/mpt_circuit/extension.rs b/zkevm-circuits/src/mpt_circuit/extension.rs
@@ -1,4 +1,4 @@
-use eth_types::Field;
+use eth_types::{Field, OpsIdentity};
 use gadgets::util::{pow, Scalar};
 use halo2_proofs::plonk::{Error, Expression, VirtualCells};
 

diff --git a/zkevm-circuits/src/mpt_circuit/extension_branch.rs b/zkevm-circuits/src/mpt_circuit/extension_branch.rs
@@ -1,4 +1,4 @@
-use eth_types::Field;
+use eth_types::{Field, OpsIdentity};
 use gadgets::util::Scalar;
 use halo2_proofs::plonk::{Error, Expression, VirtualCells};
 
@@ -291,7 +291,7 @@ impl<F: Field> ExtensionBranchConfig<F> {
                     mod_node_hash_rlc[is_s.idx()],
                     false,
                     false,
-                    Word::zero_f(),
+                    Word::zero(),
                 )?;
             } else {
                 KeyData::witness_store(

diff --git a/zkevm-circuits/src/mpt_circuit/helpers.rs b/zkevm-circuits/src/mpt_circuit/helpers.rs
@@ -27,7 +27,7 @@ use crate::{
         Challenges, Expr,
     },
 };
-use eth_types::{Field, Word as U256};
+use eth_types::{Field, OpsIdentity, Word as U256};
 use gadgets::util::{not, or, pow, xor, Scalar};
 use halo2_proofs::{
     circuit::Value,

diff --git a/zkevm-circuits/src/mpt_circuit/start.rs b/zkevm-circuits/src/mpt_circuit/start.rs
@@ -15,7 +15,7 @@ use crate::{
     },
     util::word::Word,
 };
-use eth_types::Field;
+use eth_types::{Field, OpsIdentity};
 use gadgets::util::Scalar;
 use halo2_proofs::plonk::{Error, VirtualCells};
 
@@ -96,7 +96,7 @@ impl<F: Field> StartConfig<F> {
         self.proof_type
             .assign(region, offset, start.proof_type.scalar())?;
 
-        let mut root = vec![Word::zero_f(); 2];
+        let mut root = vec![Word::zero(); 2];
         for is_s in [true, false] {
             root[is_s.idx()] = rlp_values[is_s.idx()].word();
         }

diff --git a/zkevm-circuits/src/mpt_circuit/storage_leaf.rs b/zkevm-circuits/src/mpt_circuit/storage_leaf.rs
@@ -1,4 +1,4 @@
-use eth_types::{Field, U256};
+use eth_types::{Field, OpsIdentity, U256};
 use gadgets::util::Scalar;
 use halo2_proofs::{
     circuit::Value,
@@ -191,7 +191,7 @@ impl<F: Field> StorageLeafConfig<F> {
 
                     // Placeholder leaves default to value `0`.
                     ifx! {is_placeholder_leaf => {
-                        require!(value_word[is_s.idx()] => Word::zero());
+                        require!(value_word[is_s.idx()] => Word::<Expression<F>>::zero());
                     }}
 
                     // Make sure the RLP encoding is correct.
@@ -436,7 +436,7 @@ impl<F: Field> StorageLeafConfig<F> {
         let mut key_data = vec![KeyDataWitness::default(); 2];
         let mut parent_data = vec![ParentDataWitness::default(); 2];
         let mut key_rlc = vec![0.scalar(); 2];
-        let mut value_word = vec![Word::zero_f(); 2];
+        let mut value_word = vec![Word::zero(); 2];
         for is_s in [true, false] {
             self.is_mod_extension[is_s.idx()].assign(
                 region,
@@ -596,10 +596,10 @@ impl<F: Field> StorageLeafConfig<F> {
         let mut new_value = value_word[false.idx()];
         let mut old_value = value_word[true.idx()];
         if parent_data[false.idx()].is_placeholder {
-            new_value = word::Word::zero_f();
+            new_value = word::Word::zero();
         } else if is_non_existing_proof {
-            new_value = word::Word::zero_f();
-            old_value = word::Word::zero_f();
+            new_value = word::Word::zero();
+            old_value = word::Word::zero();
         }
         mpt_config.mpt_table.assign_cached(
             region,

diff --git a/zkevm-circuits/src/util/word.rs b/zkevm-circuits/src/util/word.rs
@@ -4,7 +4,7 @@
 //   limb is 256/4 = 64 bits
 
 use bus_mapping::state_db::CodeDB;
-use eth_types::{Field, ToLittleEndian, H160, H256};
+use eth_types::{Field, OpsIdentity, ToLittleEndian, H160, H256};
 use gadgets::util::{not, or, Expr};
 use halo2_proofs::{
     circuit::{AssignedCell, Region, Value},
@@ -267,6 +267,17 @@ impl<F: Field> From<eth_types::Word> for Word<F> {
     }
 }
 
+impl<T: Clone + OpsIdentity<Output = T>> OpsIdentity for Word<T> {
+    /// output type
+    type Output = Word<T>;
+    fn zero() -> Self::Output {
+        Word::new([T::zero(), T::zero()])
+    }
+    fn one() -> Self::Output {
+        Word::new([T::one(), T::zero()])
+    }
+}
+
 impl<F: Field> From<H256> for Word<F> {
     /// Construct the word from H256
     fn from(h: H256) -> Self {
@@ -354,16 +365,6 @@ impl<F: Field, T: Expr<F> + Clone> WordExpr<F> for Word<T> {
 }
 
 impl<F: Field> Word<F> {
-    /// zero word
-    pub fn zero_f() -> Self {
-        Self::new([F::ZERO, F::ZERO])
-    }
-
-    /// one word
-    pub fn one_f() -> Self {
-        Self::new([F::ONE, F::ZERO])
-    }
-
     /// Convert address (h160) to single field element.
     /// This method is Address specific
     pub fn compress_f(&self) -> F {
@@ -376,15 +377,6 @@ impl<F: Field> Word<Expression<F>> {
     pub fn from_lo_unchecked(lo: Expression<F>) -> Self {
         Self::new([lo, 0.expr()])
     }
-    /// zero word
-    pub fn zero() -> Self {
-        Self::new([0.expr(), 0.expr()])
-    }
-
-    /// one word
-    pub fn one() -> Self {
-        Self::new([1.expr(), 0.expr()])
-    }
 
     /// select based on selector. Here assume selector is 1/0 therefore no overflow check
     pub fn select<T: Expr<F> + Clone>(