chore(l2): forbid as conversions (#1347)

**Motivation**
- This PR aims to remove all `as` conversions from the l2 code


**Description**
- This PR removes all type conversions using as and changes them to use
either into(), try_into() or refactors to avoid having to convert
- Some type conversions from enum to numeric types are removed by
implementing the trait `From`



Closes #1268

---------

Co-authored-by: Federico Borello <[email protected]>

crates/common/types/block.rs

@@ -350,7 +350,7 @@ pub fn calculate_base_fee_per_blob_gas(parent_excess_blob_gas: u64) -> u64 {
 }
 
 // Defined in [EIP-4844](https://eips.ethereum.org/EIPS/eip-4844)
-fn fake_exponential(factor: u64, numerator: u64, denominator: u64) -> u64 {
+pub fn fake_exponential(factor: u64, numerator: u64, denominator: u64) -> u64 {
     let mut i = 1;
     let mut output = 0;
     let mut numerator_accum = factor * denominator;

crates/common/types/transaction.rs

@@ -135,6 +135,18 @@ pub enum TxType {
     Privileged = 0x7e,
 }
 
+impl From<TxType> for u8 {
+    fn from(val: TxType) -> Self {
+        match val {
+            TxType::Legacy => 0x00,
+            TxType::EIP2930 => 0x01,
+            TxType::EIP1559 => 0x02,
+            TxType::EIP4844 => 0x03,
+            TxType::Privileged => 0x7e,
+        }
+    }
+}
+
 pub trait Signable {
     fn sign(&self, private_key: &SecretKey) -> Self
     where

crates/l2/Cargo.toml

@@ -44,3 +44,5 @@ path = "./l2.rs"
 unwrap_used = "deny"
 expect_used = "deny"
 indexing_slicing = "deny"
+as_conversions = "deny"
+unnecessary_cast = "warn"

crates/l2/contracts/Cargo.toml

@@ -29,3 +29,5 @@ path = "./deployer.rs"
 unwrap_used = "deny"
 expect_used = "deny"
 indexing_slicing = "deny"
+as_conversions = "deny"
+unnecessary_cast = "warn"

crates/l2/proposer/errors.rs

@@ -103,6 +103,8 @@ pub enum CommitterError {
     InvalidWithdrawalTransaction,
     #[error("Blob estimation failed: {0}")]
     BlobEstimationError(#[from] BlobEstimationError),
+    #[error("length does not fit in u16")]
+    TryIntoError(#[from] std::num::TryFromIntError),
 }
 
 #[derive(Debug, thiserror::Error)]
@@ -131,4 +133,6 @@ pub enum StateDiffError {
     BytecodeAndBytecodeHashSet,
     #[error("Empty account diff")]
     EmptyAccountDiff,
+    #[error("The length of the vector is too big to fit in u16: {0}")]
+    LengthTooBig(#[from] core::num::TryFromIntError),
 }

crates/l2/proposer/l1_committer.rs

@@ -12,16 +12,16 @@ use crate::{
 use bytes::Bytes;
 use ethrex_core::{
     types::{
-        blobs_bundle, BlobsBundle, Block, PrivilegedL2Transaction, PrivilegedTxType, Transaction,
-        TxKind, BLOB_BASE_FEE_UPDATE_FRACTION,
+        blobs_bundle, fake_exponential, BlobsBundle, Block, PrivilegedL2Transaction,
+        PrivilegedTxType, Transaction, TxKind, BLOB_BASE_FEE_UPDATE_FRACTION,
+        MIN_BASE_FEE_PER_BLOB_GAS,
     },
     Address, H256, U256,
 };
 use ethrex_storage::{error::StoreError, Store};
 use ethrex_vm::{evm_state, execute_block, get_state_transitions};
 use keccak_hash::keccak;
 use secp256k1::SecretKey;
-use std::f64::consts::E;
 use std::{collections::HashMap, time::Duration};
 use tokio::time::sleep;
 use tracing::{error, info};
@@ -211,9 +211,13 @@ impl Committer {
 
     pub fn get_deposit_hash(&self, deposit_hashes: Vec<H256>) -> Result<H256, CommitterError> {
         if !deposit_hashes.is_empty() {
+            let deposit_hashes_len: u16 = deposit_hashes
+                .len()
+                .try_into()
+                .map_err(CommitterError::from)?;
             Ok(H256::from_slice(
                 [
-                    &(deposit_hashes.len() as u16).to_be_bytes(),
+                    &deposit_hashes_len.to_be_bytes(),
                     keccak(
                         deposit_hashes
                             .iter()
@@ -270,7 +274,9 @@ impl Committer {
                         .clone()
                         .ok_or(CommitterError::FailedToRetrieveDataFromStorage)?
                         .nonce
-                        - prev_nonce) as u16,
+                        - prev_nonce)
+                        .try_into()
+                        .map_err(CommitterError::from)?,
                     storage: account_update.added_storage.clone().into_iter().collect(),
                     bytecode: account_update.code.clone(),
                     bytecode_hash: None,
@@ -347,7 +353,7 @@ impl Committer {
         let le_bytes = estimate_blob_gas(
             &self.eth_client,
             self.arbitrary_base_blob_gas_price,
-            1.2, // 20% of headroom
+            20, // 20% of headroom
         )
         .await?
         .to_le_bytes();
@@ -393,7 +399,7 @@ impl Committer {
 /// # Parameters:
 /// - `eth_client`: The Ethereum client used to fetch the latest block.
 /// - `arbitrary_base_blob_gas_price`: The base gas price that serves as the minimum price for blob transactions.
-/// - `headroom`: A multiplier (as a float) applied to the estimated gas price to provide a buffer against fluctuations.
+/// - `headroom`: Percentage applied to the estimated gas price to provide a buffer against fluctuations.
 ///
 /// # Formula:
 /// The gas price is estimated using an exponential function based on the blob gas used in the latest block and the
@@ -404,7 +410,7 @@ impl Committer {
 async fn estimate_blob_gas(
     eth_client: &EthClient,
     arbitrary_base_blob_gas_price: u64,
-    headroom: f64,
+    headroom: u64,
 ) -> Result<u64, CommitterError> {
     let latest_block = eth_client
         .get_block_by_number(BlockByNumber::Latest)
@@ -432,15 +438,16 @@ async fn estimate_blob_gas(
     };
 
     // If the blob's market is in high demand, the equation may give a really big number.
-    let exponent = (total_blob_gas as f64) / (BLOB_BASE_FEE_UPDATE_FRACTION as f64);
-    let blob_gas = match E.powf(exponent) {
-        result if result.is_finite() => result,
-        _ => return Err(BlobEstimationError::NonFiniteResult.into()),
-    };
+    let blob_gas = fake_exponential(
+        MIN_BASE_FEE_PER_BLOB_GAS,
+        total_blob_gas,
+        BLOB_BASE_FEE_UPDATE_FRACTION,
+    );
+
+    let gas_with_headroom = (blob_gas * (100 + headroom)) / 100;
 
     // Check if we have an overflow when we take the headroom into account.
-    let gas_with_headroom = blob_gas * headroom;
-    let blob_gas = match arbitrary_base_blob_gas_price.checked_add(gas_with_headroom as u64) {
+    let blob_gas = match arbitrary_base_blob_gas_price.checked_add(gas_with_headroom) {
         Some(gas) => gas,
         None => return Err(BlobEstimationError::OverflowError.into()),
     };

crates/l2/proposer/prover_server.rs

@@ -417,7 +417,12 @@ impl ProverServer {
         calldata.extend(journal_digest.as_bytes());
 
         // extend with size of seal
-        calldata.extend(H256::from_low_u64_be(seal.len() as u64).as_bytes());
+        calldata.extend(
+            H256::from_low_u64_be(seal.len().try_into().map_err(|err| {
+                ProverServerError::Custom(format!("Seal length does not fit in u64: {}", err))
+            })?)
+            .as_bytes(),
+        );
         // extend with seal
         calldata.extend(seal);
         // extend with zero padding

crates/l2/proposer/state_diff.rs

@@ -69,15 +69,32 @@ impl Default for StateDiff {
     }
 }
 
+impl From<AccountStateDiffType> for u8 {
+    fn from(value: AccountStateDiffType) -> Self {
+        match value {
+            AccountStateDiffType::NewBalance => 1,
+            AccountStateDiffType::NonceDiff => 2,
+            AccountStateDiffType::Storage => 4,
+            AccountStateDiffType::Bytecode => 8,
+            AccountStateDiffType::BytecodeHash => 16,
+        }
+    }
+}
+
 impl StateDiff {
     pub fn encode(&self) -> Result<Bytes, StateDiffError> {
         if self.version != 1 {
             return Err(StateDiffError::UnsupportedVersion(self.version));
         }
+        let modified_accounts_len: u16 = self
+            .modified_accounts
+            .len()
+            .try_into()
+            .map_err(StateDiffError::from)?;
 
         let mut encoded: Vec<u8> = Vec::new();
         encoded.push(self.version);
-        encoded.extend((self.modified_accounts.len() as u16).to_be_bytes());
+        encoded.extend(modified_accounts_len.to_be_bytes());
 
         for (address, diff) in &self.modified_accounts {
             let (r#type, diff_encoded) = diff.encode()?;
@@ -119,20 +136,28 @@ impl AccountStateDiff {
         let mut encoded: Vec<u8> = Vec::new();
 
         if let Some(new_balance) = self.new_balance {
-            r#type += AccountStateDiffType::NewBalance as u8;
+            let r_type: u8 = AccountStateDiffType::NewBalance.into();
+            r#type += r_type;
             let buf = &mut [0u8; 32];
             new_balance.to_big_endian(buf);
             encoded.extend_from_slice(buf);
         }
 
         if self.nonce_diff != 0 {
-            r#type += AccountStateDiffType::NonceDiff as u8;
+            let r_type: u8 = AccountStateDiffType::NonceDiff.into();
+            r#type += r_type;
             encoded.extend(self.nonce_diff.to_be_bytes());
         }
 
         if !self.storage.is_empty() {
-            r#type += AccountStateDiffType::Storage as u8;
-            encoded.extend((self.storage.len() as u16).to_be_bytes());
+            let r_type: u8 = AccountStateDiffType::Storage.into();
+            let storage_len: u16 = self
+                .storage
+                .len()
+                .try_into()
+                .map_err(StateDiffError::from)?;
+            r#type += r_type;
+            encoded.extend(storage_len.to_be_bytes());
             for (key, value) in &self.storage {
                 encoded.extend_from_slice(&key.0);
                 let buf = &mut [0u8; 32];
@@ -142,13 +167,20 @@ impl AccountStateDiff {
         }
 
         if let Some(bytecode) = &self.bytecode {
-            r#type += AccountStateDiffType::Bytecode as u8;
-            encoded.extend((bytecode.len() as u16).to_be_bytes());
+            let r_type: u8 = AccountStateDiffType::Bytecode.into();
+            let bytecode_len: u16 = self
+                .storage
+                .len()
+                .try_into()
+                .map_err(StateDiffError::from)?;
+            r#type += r_type;
+            encoded.extend(bytecode_len.to_be_bytes());
             encoded.extend(bytecode);
         }
 
         if let Some(bytecode_hash) = &self.bytecode_hash {
-            r#type += AccountStateDiffType::BytecodeHash as u8;
+            let r_type: u8 = AccountStateDiffType::BytecodeHash.into();
+            r#type += r_type;
             encoded.extend(&bytecode_hash.0);
         }
 

crates/l2/prover/Cargo.toml

@@ -55,3 +55,5 @@ gpu = ["risc0-zkvm/cuda"]
 unwrap_used = "deny"
 expect_used = "deny"
 indexing_slicing = "deny"
+as_conversions = "deny"
+unnecessary_cast = "warn"

crates/l2/sdk/Cargo.toml

@@ -24,3 +24,5 @@ path = "src/sdk.rs"
 unwrap_used = "deny"
 expect_used = "deny"
 indexing_slicing = "deny"
+as_conversions = "deny"
+unnecessary_cast = "warn"

crates/l2/sdk/src/sdk.rs

@@ -258,7 +258,7 @@ pub async fn get_withdraw_merkle_proof(
             Transaction::PrivilegedL2Transaction(privileged_l2_transaction) => {
                 privileged_l2_transaction
                     .get_withdrawal_hash()
-                    .map(|withdrawal_hash| (i as u64, (withdrawal_hash)))
+                    .map(|withdrawal_hash| (i, (withdrawal_hash)))
             }
             _ => unreachable!(),
         })
@@ -283,5 +283,10 @@ pub async fn get_withdraw_merkle_proof(
         "Failed to generate merkle proof, element is not on the tree".to_string(),
     ))?;
 
-    Ok((index, path))
+    Ok((
+        index
+            .try_into()
+            .map_err(|err| EthClientError::Custom(format!("index does not fit in u64: {}", err)))?,
+        path,
+    ))
 }

crates/l2/utils/eth_client/eth_sender.rs

@@ -90,7 +90,11 @@ impl EthClient {
         let encoded_from = deployer.encode_to_vec();
         // FIXME: We'll probably need to use nonce - 1 since it was updated above.
         let encoded_nonce = self.get_nonce(deployer).await?.encode_to_vec();
-        let mut encoded = vec![(0xc0 + encoded_from.len() + encoded_nonce.len()) as u8];
+        let mut encoded = vec![(0xc0 + encoded_from.len() + encoded_nonce.len())
+            .try_into()
+            .map_err(|err| {
+                EthClientError::Custom(format!("Failed to encode deployed_address {}", err))
+            })?];
         encoded.extend(encoded_from.clone());
         encoded.extend(encoded_nonce.clone());
         let deployed_address = Address::from(keccak(encoded));