C-01 Fix [PAG]

src/InterestRate.sol

@@ -325,9 +325,13 @@ contract InterestRate {
         if (distributionFactor == 0) {
             return (ilkData.minimumKinkRate, ilkData.reserveFactor.scaleUpToRay(4));
         }
+
+        // If the `totalEthSupply` is small enough to truncate to zero, then
+        // treat the utilization as zero.
+        uint256 totalEthSupplyScaled = totalEthSupply.wadMulDown(distributionFactor.scaleUpToWad(4));
+
         // [RAD] / [WAD] = [RAY]
-        uint256 utilizationRate =
-            totalEthSupply == 0 ? 0 : totalIlkDebt / (totalEthSupply.wadMulDown(distributionFactor.scaleUpToWad(4)));
+        uint256 utilizationRate = totalEthSupplyScaled == 0 ? 0 : totalIlkDebt / totalEthSupplyScaled;
 
         // Avoid stack too deep
         uint256 adjustedBelowKinkSlope;

src/IonPool.sol

@@ -364,7 +364,7 @@ contract IonPool is PausableUpgradeable, RewardToken {
     function _accrueInterest() internal returns (uint256 newTotalDebt) {
         IonPoolStorage storage $ = _getIonPoolStorage();
 
-        uint256 totalEthSupply = getTotalUnderlyingClaimsUnaccrued();
+        uint256 totalEthSupply = totalSupplyUnaccrued();
 
         uint256 totalSupplyFactorIncrease;
         uint256 totalTreasuryMintAmount;
@@ -419,7 +419,7 @@ contract IonPool is PausableUpgradeable, RewardToken {
         rateIncreases = new uint104[](ilksLength);
         timestampIncreases = new uint48[](ilksLength);
 
-        uint256 totalEthSupply = getTotalUnderlyingClaimsUnaccrued();
+        uint256 totalEthSupply = totalSupplyUnaccrued();
 
         for (uint8 i = 0; i < ilksLength;) {
             (
@@ -457,7 +457,7 @@ contract IonPool is PausableUpgradeable, RewardToken {
         returns (uint104 newRateIncrease, uint48 timestampIncrease)
     {
         (,, newRateIncrease,, timestampIncrease) =
-            _calculateRewardAndDebtDistributionForIlk(ilkIndex, getTotalUnderlyingClaimsUnaccrued());
+            _calculateRewardAndDebtDistributionForIlk(ilkIndex, totalSupplyUnaccrued());
     }
 
     function _calculateRewardAndDebtDistributionForIlk(
@@ -478,7 +478,10 @@ contract IonPool is PausableUpgradeable, RewardToken {
         Ilk storage ilk = $.ilks[ilkIndex];
 
         uint256 _totalNormalizedDebt = ilk.totalNormalizedDebt;
-        if (_totalNormalizedDebt == 0 || block.timestamp == ilk.lastRateUpdate) {
+        // Because all interest that would have accrued during a pause is
+        // cancelled upon `unpause`, we return zero interest while markets are
+        // paused.
+        if (_totalNormalizedDebt == 0 || block.timestamp == ilk.lastRateUpdate || paused()) {
             // Unsafe cast OK
             // block.timestamp - ilk.lastRateUpdate will almost always be 0
             // here. The exception is on first borrow.
@@ -490,14 +493,14 @@ contract IonPool is PausableUpgradeable, RewardToken {
         (uint256 borrowRate, uint256 reserveFactor) =
             $.interestRateModule.calculateInterestRate(ilkIndex, totalDebt, totalEthSupply);
 
-        if (borrowRate == 0) return (0, 0, 0, 0, 0);
-
-        // Calculates borrowRate ^ (time) and returns the result with RAY precision
-        uint256 borrowRateExpT = _rpow(borrowRate + RAY, block.timestamp - ilk.lastRateUpdate, RAY);
-
         // Unsafe cast OK
         timestampIncrease = uint48(block.timestamp) - ilk.lastRateUpdate;
 
+        if (borrowRate == 0) return (0, 0, 0, 0, timestampIncrease);
+
+        // Calculates borrowRate ^ (time) and returns the result with RAY precision
+        uint256 borrowRateExpT = _rpow(borrowRate + RAY, timestampIncrease, RAY);
+
         // Debt distribution
         // This form of rate accrual is much safer than distributing the new
         // debt increase to the total debt since low debt amounts won't cause
@@ -512,7 +515,7 @@ contract IonPool is PausableUpgradeable, RewardToken {
         newDebtIncrease = _totalNormalizedDebt * newRateIncrease; // [RAD]
 
         // Income distribution
-        uint256 _normalizedTotalSupply = totalSupplyUnaccrued(); // [WAD]
+        uint256 _normalizedTotalSupply = normalizedTotalSupplyUnaccrued(); // [WAD]
 
         // If there is no supply, then nothing is being lent out.
         supplyFactorIncrease = _normalizedTotalSupply == 0
@@ -570,7 +573,7 @@ contract IonPool is PausableUpgradeable, RewardToken {
 
         uint256 _supplyCap = $.supplyCap;
 
-        if (getTotalUnderlyingClaims() > _supplyCap) revert DepositSurpassesSupplyCap(amount, _supplyCap);
+        if (totalSupply() > _supplyCap) revert DepositSurpassesSupplyCap(amount, _supplyCap);
 
         emit Supply(user, _msgSender(), amount, _supplyFactor, newTotalDebt);
     }
@@ -954,7 +957,7 @@ contract IonPool is PausableUpgradeable, RewardToken {
     function getCurrentBorrowRate(uint8 ilkIndex) external view returns (uint256 borrowRate, uint256 reserveFactor) {
         IonPoolStorage storage $ = _getIonPoolStorage();
 
-        uint256 totalEthSupply = getTotalUnderlyingClaimsUnaccrued();
+        uint256 totalEthSupply = totalSupplyUnaccrued();
 
         uint256 _totalNormalizedDebt = $.ilks[ilkIndex].totalNormalizedDebt;
         uint256 _rate = $.ilks[ilkIndex].rate;

src/interfaces/IIonPool.sol

@@ -234,4 +234,5 @@ interface IIonPool {
     function getTotalUnderlyingClaims() external view returns (uint256);
     function getUnderlyingClaimOf(address user) external view returns (uint256);
     function extsload(bytes32 slot) external view returns (bytes32);
+    function balanceOfUnaccrued(address user) external view returns (uint256);
 }

src/token/RewardToken.sol

@@ -333,8 +333,6 @@ abstract contract RewardToken is
             $._normalizedBalances[from] = oldSenderBalance - amountNormalized;
         }
         $._normalizedBalances[to] += amountNormalized;
-
-        emit Transfer(from, to, amountNormalized);
     }
 
     /**
@@ -450,22 +448,30 @@ abstract contract RewardToken is
     }
 
     /**
-     * @dev Current token balance
+     * @dev Current claim of the underlying token inclusive of interest to be accrued.
      * @param user to get balance of
      */
-    function getUnderlyingClaimOf(address user) public view returns (uint256) {
+    function balanceOf(address user) public view returns (uint256) {
         RewardTokenStorage storage $ = _getRewardTokenStorage();
 
         (uint256 totalSupplyFactorIncrease,,,,) = calculateRewardAndDebtDistribution();
 
         return $._normalizedBalances[user].rayMulDown($.supplyFactor + totalSupplyFactorIncrease);
     }
 
+    /**
+     * @dev Current claim of the underlying token without accounting for interest to be accrued.
+     */
+    function balanceOfUnaccrued(address user) public view returns (uint256) {
+        RewardTokenStorage storage $ = _getRewardTokenStorage();
+        return $._normalizedBalances[user].rayMulDown($.supplyFactor);
+    }
+
     /**
      * @dev Accounting is done in normalized balances
      * @param user to get normalized balance of
      */
-    function balanceOf(address user) external view returns (uint256) {
+    function normalizedBalanceOf(address user) external view returns (uint256) {
         RewardTokenStorage storage $ = _getRewardTokenStorage();
         return $._normalizedBalances[user];
     }
@@ -494,7 +500,10 @@ abstract contract RewardToken is
         return $.treasury;
     }
 
-    function getTotalUnderlyingClaimsUnaccrued() public view returns (uint256) {
+    /**
+     * @dev Total claim of the underlying asset belonging to lenders not inclusive of the new interest to be accrued.
+     */
+    function totalSupplyUnaccrued() public view returns (uint256) {
         RewardTokenStorage storage $ = _getRewardTokenStorage();
 
         uint256 _normalizedTotalSupply = $.normalizedTotalSupply;
@@ -507,9 +516,9 @@ abstract contract RewardToken is
     }
 
     /**
-     * @dev Total claim of the underlying asset belonging to lenders.
+     * @dev Total claim of the underlying asset belonging to lender inclusive of the new interest to be accrued.
      */
-    function getTotalUnderlyingClaims() public view returns (uint256) {
+    function totalSupply() public view returns (uint256) {
         RewardTokenStorage storage $ = _getRewardTokenStorage();
 
         uint256 _normalizedTotalSupply = $.normalizedTotalSupply;
@@ -518,22 +527,20 @@ abstract contract RewardToken is
             return 0;
         }
 
-        (uint256 totalSupplyFactorIncrease,,,,) = calculateRewardAndDebtDistribution();
+        (uint256 totalSupplyFactorIncrease, uint256 totalTreasuryMintAmount,,,) = calculateRewardAndDebtDistribution();
 
-        return _normalizedTotalSupply.rayMulDown($.supplyFactor + totalSupplyFactorIncrease);
+        return _normalizedTotalSupply.rayMulDown($.supplyFactor + totalSupplyFactorIncrease) + totalTreasuryMintAmount;
     }
 
-    function totalSupplyUnaccrued() public view returns (uint256) {
+    function normalizedTotalSupplyUnaccrued() public view returns (uint256) {
         RewardTokenStorage storage $ = _getRewardTokenStorage();
         return $.normalizedTotalSupply;
     }
 
     /**
-     * @dev Current total supply
-     *
-     * Normalized total supply and total supply are same in non-rebasing token.
+     * @dev Normalized total supply.
      */
-    function totalSupply() public view returns (uint256) {
+    function normalizedTotalSupply() public view returns (uint256) {
         RewardTokenStorage storage $ = _getRewardTokenStorage();
 
         (uint256 totalSupplyFactorIncrease, uint256 totalTreasuryMintAmount,,,) = calculateRewardAndDebtDistribution();