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         // This makes impossible to open a trove with zero withdrawn Bold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,