Merge pull request #157 from liquity/reduce_liquidation_penalty

Reduce liquidation penalty

contracts/src/BorrowerOperations.sol

@@ -23,13 +23,16 @@ contract BorrowerOperations is LiquityBase, Ownable, CheckContract, IBorrowerOpe
  // --- Connected contract declarations ---
 
  IERC20 public immutable ETH;
- ITroveManager public troveManager;
+ ITroveManager public immutable troveManager;
  address gasPoolAddress;
  ICollSurplusPool collSurplusPool;
  IBoldToken public boldToken;
  // A doubly linked list of Troves, sorted by their collateral ratios
  ISortedTroves public sortedTroves;
 
+ // Minimum collateral ratio for individual troves
+ uint256 public immutable MCR;
+
  /* --- Variable container structs ---
 
  Used to hold, return and assign variables inside a function, in order to avoid the error:
@@ -97,15 +100,21 @@ contract BorrowerOperations is LiquityBase, Ownable, CheckContract, IBorrowerOpe
  );
  event BoldBorrowingFeePaid(uint256 indexed _troveId, uint256 _boldFee);
 
- constructor(address _ETHAddress) {
- checkContract(_ETHAddress);
- ETH = IERC20(_ETHAddress);
+ constructor(IERC20 _ETH, ITroveManager _troveManager) {
+ checkContract(address(_ETH));
+ checkContract(address(_troveManager));
+
+ ETH = _ETH;
+ troveManager = _troveManager;
+
+ MCR = _troveManager.MCR();
+
+ emit TroveManagerAddressChanged(address(_troveManager));
  }
 
  // --- Dependency setters ---
 
  function setAddresses(
- address _troveManagerAddress,
  address _activePoolAddress,
  address _defaultPoolAddress,
  address _gasPoolAddress,
@@ -117,7 +126,6 @@ contract BorrowerOperations is LiquityBase, Ownable, CheckContract, IBorrowerOpe
  // This makes impossible to open a trove with zero withdrawn Bold
  assert(MIN_NET_DEBT > 0);
 
- checkContract(_troveManagerAddress);
  checkContract(_activePoolAddress);
  checkContract(_defaultPoolAddress);
  checkContract(_gasPoolAddress);
@@ -126,7 +134,6 @@ contract BorrowerOperations is LiquityBase, Ownable, CheckContract, IBorrowerOpe
  checkContract(_sortedTrovesAddress);
  checkContract(_boldTokenAddress);
 
- troveManager = ITroveManager(_troveManagerAddress);
  activePool = IActivePool(_activePoolAddress);
  defaultPool = IDefaultPool(_defaultPoolAddress);
  gasPoolAddress = _gasPoolAddress;
@@ -135,7 +142,6 @@ contract BorrowerOperations is LiquityBase, Ownable, CheckContract, IBorrowerOpe
  sortedTroves = ISortedTroves(_sortedTrovesAddress);
  boldToken = IBoldToken(_boldTokenAddress);
 
- emit TroveManagerAddressChanged(_troveManagerAddress);
  emit ActivePoolAddressChanged(_activePoolAddress);
  emit DefaultPoolAddressChanged(_defaultPoolAddress);
  emit GasPoolAddressChanged(_gasPoolAddress);
@@ -501,13 +507,11 @@ contract BorrowerOperations is LiquityBase, Ownable, CheckContract, IBorrowerOpe
  }
 
  /**
- * Claim remaining collateral from a redemption or from a liquidation with ICR > MCR in Recovery Mode
+ * Claim remaining collateral from a liquidation with ICR exceeding the liquidation penalty
  */
- function claimCollateral(uint256 _troveId) external override {
- _requireIsOwner(_troveId);
-
+ function claimCollateral() external override {
  // send ETH from CollSurplus Pool to owner
- collSurplusPool.claimColl(msg.sender, _troveId);
+ collSurplusPool.claimColl(msg.sender);
  }
 
  // --- Helper functions ---
@@ -726,7 +730,7 @@ contract BorrowerOperations is LiquityBase, Ownable, CheckContract, IBorrowerOpe
  }
  }
 
- function _requireICRisAboveMCR(uint256 _newICR) internal pure {
+ function _requireICRisAboveMCR(uint256 _newICR) internal view {
  require(_newICR >= MCR, "BorrowerOps: An operation that would result in ICR < MCR is not permitted");
  }
 

contracts/src/CollSurplusPool.sol

@@ -6,9 +6,8 @@ import "openzeppelin-contracts/contracts/token/ERC20/utils/SafeERC20.sol";
 
 import "./Interfaces/ICollSurplusPool.sol";
 import "./Dependencies/Ownable.sol";
-import "./Dependencies/CheckContract.sol";
 
-contract CollSurplusPool is Ownable, CheckContract, ICollSurplusPool {
+contract CollSurplusPool is Ownable, ICollSurplusPool {
  using SafeERC20 for IERC20;
 
  string public constant NAME = "CollSurplusPool";
@@ -21,19 +20,18 @@ contract CollSurplusPool is Ownable, CheckContract, ICollSurplusPool {
  // deposited ether tracker
  uint256 internal ETHBalance;
  // Collateral surplus claimable by trove owners
- mapping(uint256 => uint256) internal balances;
+ mapping(address => uint256) internal balances;
 
  // --- Events ---
 
  event BorrowerOperationsAddressChanged(address _newBorrowerOperationsAddress);
  event TroveManagerAddressChanged(address _newTroveManagerAddress);
  event ActivePoolAddressChanged(address _newActivePoolAddress);
 
- event CollBalanceUpdated(uint256 indexed _troveId, uint256 _newBalance);
+ event CollBalanceUpdated(address indexed _account, uint256 _newBalance);
  event EtherSent(address _to, uint256 _amount);
 
  constructor(address _ETHAddress) {
- checkContract(_ETHAddress);
  ETH = IERC20(_ETHAddress);
  }
 
@@ -44,10 +42,6 @@ contract CollSurplusPool is Ownable, CheckContract, ICollSurplusPool {
  override
  onlyOwner
  {
- checkContract(_borrowerOperationsAddress);
- checkContract(_troveManagerAddress);
- checkContract(_activePoolAddress);
-
  borrowerOperationsAddress = _borrowerOperationsAddress;
  troveManagerAddress = _troveManagerAddress;
  activePoolAddress = _activePoolAddress;
@@ -65,29 +59,29 @@ contract CollSurplusPool is Ownable, CheckContract, ICollSurplusPool {
  return ETHBalance;
  }
 
- function getCollateral(uint256 _troveId) external view override returns (uint256) {
- return balances[_troveId];
+ function getCollateral(address _account) external view override returns (uint256) {
+ return balances[_account];
  }
 
  // --- Pool functionality ---
 
- function accountSurplus(uint256 _troveId, uint256 _amount) external override {
+ function accountSurplus(address _account, uint256 _amount) external override {
  _requireCallerIsTroveManager();
 
- uint256 newAmount = balances[_troveId] + _amount;
- balances[_troveId] = newAmount;
+ uint256 newAmount = balances[_account] + _amount;
+ balances[_account] = newAmount;
  ETHBalance = ETHBalance + _amount;
 
- emit CollBalanceUpdated(_troveId, newAmount);
+ emit CollBalanceUpdated(_account, newAmount);
  }
 
- function claimColl(address _account, uint256 _troveId) external override {
+ function claimColl(address _account) external override {
  _requireCallerIsBorrowerOperations();
- uint256 claimableColl = balances[_troveId];
+ uint256 claimableColl = balances[_account];
  require(claimableColl > 0, "CollSurplusPool: No collateral available to claim");
 
- balances[_troveId] = 0;
- emit CollBalanceUpdated(_troveId, 0);
+ balances[_account] = 0;
+ emit CollBalanceUpdated(_account, 0);
 
  ETHBalance = ETHBalance - claimableColl;
  emit EtherSent(_account, claimableColl);

contracts/src/Dependencies/LiquityBase.sol

@@ -20,9 +20,6 @@ contract LiquityBase is BaseMath, ILiquityBase {
 
  uint256 public constant _100pct = 1000000000000000000; // 1e18 == 100%
 
- // Minimum collateral ratio for individual troves
- uint256 public constant MCR = 1100000000000000000; // 110%
-
  // Critical system collateral ratio. If the system's total collateral ratio (TCR) falls below the CCR, some borrowing operation restrictions are applied
  uint256 public constant CCR = 1500000000000000000; // 150%
 

contracts/src/Dependencies/LiquityMath.sol

@@ -13,6 +13,10 @@ library LiquityMath {
  return (_a >= _b) ? _a : _b;
  }
 
+ function _sub_min_0(uint256 _a, uint256 _b) internal pure returns (uint256) {
+ return (_a > _b) ? _a - _b : 0;
+ }
+
  /* 
  * Multiply two decimal numbers and use normal rounding rules:
  * -round product up if 19'th mantissa digit >= 5

contracts/src/Interfaces/IBorrowerOperations.sol

@@ -13,7 +13,6 @@ interface IBorrowerOperations is ILiquityBase {
  function sortedTroves() external view returns (ISortedTroves);
 
  function setAddresses(
- address _troveManagerAddress,
  address _activePoolAddress,
  address _defaultPoolAddress,
  address _gasPoolAddress,
@@ -61,7 +60,7 @@ interface IBorrowerOperations is ILiquityBase {
  uint256 _lowerHint
  ) external;
 
- function claimCollateral(uint256 _troveId) external;
+ function claimCollateral() external;
 
  function setAddManager(uint256 _troveId, address _manager) external;
  function setRemoveManager(uint256 _troveId, address _manager) external;

contracts/src/Interfaces/ICollSurplusPool.sol

@@ -8,9 +8,9 @@ interface ICollSurplusPool {
 
  function getETHBalance() external view returns (uint256);
 
- function getCollateral(uint256 _troveId) external view returns (uint256);
+ function getCollateral(address _account) external view returns (uint256);
 
- function accountSurplus(uint256 _troveId, uint256 _amount) external;
+ function accountSurplus(address _account, uint256 _amount) external;
 
- function claimColl(address _account, uint256 _troveId) external;
+ function claimColl(address _account) external;
 }

contracts/src/Interfaces/ILiquityBase.sol

@@ -12,6 +12,5 @@ interface ILiquityBase {
  function priceFeed() external view returns (IPriceFeed);
  function BOLD_GAS_COMPENSATION() external view returns (uint256);
  function MIN_NET_DEBT() external view returns (uint256);
- function MCR() external view returns (uint256);
  function getEntireSystemDebt() external view returns (uint256);
 }

contracts/src/Interfaces/ITroveManager.sol

@@ -11,6 +11,8 @@ import "./ISortedTroves.sol";
 
 // Common interface for the Trove Manager.
 interface ITroveManager is IERC721, ILiquityBase {
+ function MCR() external view returns (uint256);
+
  function setAddresses(
  address _borrowerOperationsAddress,
  address _activePoolAddress,