feat(tests): RESERVE_BALANCE precompile with tests

[pdobacz]

No description provided.

[greptile-apps]

Greptile Summary

This PR implements the RESERVE_BALANCE precompile (dippedIntoReserve()) at address 0x1001 for the MONAD_NINE fork (MIP-4), accompanied by an extensive test suite. The core change extracts the reserve-balance violation check into a standalone is_reserve_balance_violated() helper, adds a new RevertInMonadPrecompile exception type, and adds a delegation-revert guard so that delegating EOAs pointing to Monad-specific precompile addresses cannot execute them as empty code.

Key changes:

• New reserve_balance.py precompile: Implements dippedIntoReserve() with strict call-type enforcement (CALL only), selector/size/value validation, and GAS_WARM_ACCESS cost.
• Refactored is_reserve_balance_violated(): Extracted from the inline process_message body into a named function shared by both the end-of-transaction check and the new precompile.
• MONAD_PRECOMPILE_ADDRESSES guard: Added to both monad_eight and monad_nine interpreters to revert when a delegating EOA's code address is a Monad precompile.
• Comprehensive test suite: Covers fork transition, call opcodes, input validation, gas, revert data, multi-block delegation scenarios, value-transfer violations, and interaction with the existing tx-revert mechanism.
• Prague EIP-7702 test updates: Correctly adjusts test_set_code_to_precompile and test_pointer_to_precompile for the new Monad precompile revert behavior.

Issues found:

• Logic bug: STAKING_ADDRESS (0x1000) is included in MONAD_PRECOMPILE_ADDRESSES (both forks) but is absent from PRE_COMPILED_CONTRACTS. Because the delegation-revert guard is nested inside if code_address in PRE_COMPILED_CONTRACTS:, the elif branch for STAKING_ADDRESS is unreachable — a delegating EOA pointing to 0x1000 silently executes empty code instead of reverting.
• Debug artifact: A stray print() call was left in test_transfers.py::test_credit_same_tx and will pollute test output.

Confidence Score: 3/5

• The PR has a logic bug where the delegation-revert guard for Monad precompiles does not fire for STAKING_ADDRESS, and contains a debug print statement.
• The RESERVE_BALANCE precompile implementation itself is correct and well-tested. However, the MONAD_PRECOMPILE_ADDRESSES guard has a critical flaw: STAKING_ADDRESS is listed in the guard set but is not in PRE_COMPILED_CONTRACTS, making the elif branch unreachable for it. This means a delegating EOA pointing to 0x1000 will silently execute empty code rather than reverting, contradicting the stated invariant. This guard logic issue affects both monad_eight and monad_nine. Additionally, there is a leftover debug print() statement in test_transfers.py that should be removed before merge.
• src/ethereum/forks/monad_nine/vm/precompiled_contracts/init.py and src/ethereum/forks/monad_eight/vm/interpreter.py (STAKING_ADDRESS guard logic) and tests/monad_nine/mip4_checkreservebalance/test_transfers.py (debug print)

Sequence Diagram

sequenceDiagram
    participant Caller as Caller Contract
    participant Interp as process_message()
    participant RB as reserve_balance()
    participant Helper as is_reserve_balance_violated()

    Caller->>Interp: CALL 0x1001 (normal path)
    Note over Interp: code_address in PRE_COMPILED_CONTRACTS AND NOT disable_precompiles
    Interp->>RB: reserve_balance(evm)
    RB->>RB: _is_call() check (NOT_CALL → raise InvalidParameter)
    RB->>RB: charge_gas(GAS_WARM_ACCESS)
    RB->>RB: selector / value / size checks
    RB->>Helper: is_reserve_balance_violated(state, tx_env)
    Helper-->>RB: bool
    RB-->>Interp: evm.output = U256(violation).to_be_bytes32()
    Interp-->>Caller: return data (32 bytes)

    Caller->>Interp: CALL delegating_EOA → points to 0x1001
    Note over Interp: disable_precompiles = True, code_address in PRE_COMPILED_CONTRACTS
    Interp->>Interp: elif code_address in MONAD_PRECOMPILE_ADDRESSES → True
    Interp->>Interp: raise RevertInMonadPrecompile
    Note over Interp: gas_left = 0, evm.output preserved
    Interp-->>Caller: revert (0 return, all gas consumed)

    Caller->>Interp: CALL delegating_EOA → points to 0x1000 (STAKING)
    Note over Interp: disable_precompiles = True, code_address NOT in PRE_COMPILED_CONTRACTS
    Note over Interp: ⚠ elif never reached — executes empty code instead
    Interp-->>Caller: success (empty return)

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_{Last reviewed commit: 2b9d255}