fix: bound base rate

morpho-org · Oct 31, 2023 · c68cb45 · c68cb45
1 parent e061946
commit c68cb45
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Showing 2 changed files with 7 additions and 6 deletions.
diff --git a/src/SpeedJumpIrm.sol b/src/SpeedJumpIrm.sol
@@ -118,7 +118,10 @@ contract AdaptativeCurveIRM is IIrm {
         // Safe "unchecked" cast because elapsed <= block.timestamp.
         int256 linearVariation = speed * int256(elapsed);
         uint256 variationMultiplier = MathLib.wExp(linearVariation);
-        uint256 newBaseRate = (baseRate[id] > 0) ? baseRate[id].wMulDown(variationMultiplier) : INITIAL_BASE_RATE;
+        // newBaseRate is bounded between MIN_BASE_RATE, MAX_BASE_RATE.
+        uint256 newBaseRate = (baseRate[id] > 0)
+            ? baseRate[id].wMulDown(variationMultiplier).bound(MIN_BASE_RATE, MAX_BASE_RATE)
+            : INITIAL_BASE_RATE;
         uint256 newBorrowRate = _curve(newBaseRate, err);
 
         // Then we compute the average rate over the period (this is what Morpho needs to accrue the interest).
@@ -137,8 +140,7 @@ contract AdaptativeCurveIRM is IIrm {
                 uint256((int256(newBorrowRate) - int256(_curve(baseRate[id], err))).wDivDown(linearVariation));
         }
 
-        // We bound both newBorrowRate and avgBorrowRate between MIN_RATE and MAX_RATE.
-        return (avgBorrowRate, newBaseRate.bound(MIN_BASE_RATE, MAX_BASE_RATE));
+        return (avgBorrowRate, newBaseRate);
     }
 
     function _curve(uint256 _baseRate, int256 err) internal view returns (uint256) {

diff --git a/test/SpeedJumpIrmTest.sol b/test/SpeedJumpIrmTest.sol
@@ -150,8 +150,7 @@ contract AdaptativeCurveIRMTest is Test {
         int256 speed = int256(ADJUSTMENT_SPEED).wMulDown(err);
         uint256 elapsed = (baseRate > 0) ? block.timestamp - market.lastUpdate : 0;
         int256 linearVariation = speed * int256(elapsed);
-        uint256 variationMultiplier = MathLib.wExp(linearVariation);
-        uint256 newBaseRate = (baseRate > 0) ? baseRate.wMulDown(variationMultiplier) : INITIAL_BASE_RATE;
+        uint256 newBaseRate = _expectedBaseRate(id, market);
         uint256 newBorrowRate = _curve(newBaseRate, err);
 
         uint256 avgBorrowRate;
@@ -164,7 +163,7 @@ contract AdaptativeCurveIRMTest is Test {
         return avgBorrowRate;
     }
 
-    function _curve(uint256 baseRate, int256 err) internal view returns (uint256) {
+    function _curve(uint256 baseRate, int256 err) internal pure returns (uint256) {
         // Safe "unchecked" cast because err >= -1 (in WAD).
         if (err < 0) {
             return uint256((WAD_INT - WAD_INT.wDivDown(int256(CURVE_STEEPNESS))).wMulDown(err) + WAD_INT).wMulDown(