Incorrect calculation in limitPurchaseByAvailableAmounts

[notional-finance]

Incorrect calculation in limitPurchaseByAvailableAmounts

[jeffywu]

Fix in e9fdc88

[T-Woodward]

This is a misleading comment:

contracts-v2/contracts/internal/liquidation/LiquidatefCash.sol

Lines 232 to 234 in e9fdc88

	// in the discount factors from risk adjusted versus liquidation. A liquidator may purchase at 1000 fCash
	// at a discount factor of 0.90 but the risk adjusted discount factor is 0.95. fCashBenefit in this case
	// is 0.05 * 1000 = 50

The liquidation discount factor will be closer to 1 than the risk adjusted discount factor. In this scenario, the liquidator should purchase at a discount of .95 with a risk adjusted discount factor of .9.

[T-Woodward]

The left side of this inequality should not be fCashLiquidationPV:

contracts-v2/contracts/internal/liquidation/LiquidatefCash.sol

Line 241 in e9fdc88

if (fCashLiquidationPV > c.factors.collateralAvailable.add(fCashBenefit)) {

It should be fCashCollateralPV where:

fCashCollateralPV = fCashToLiquidate * riskAdjustedDiscountFactor

[jeffywu]

@T-Woodward is this correct then?

        int256 localToPurchase;
        (fCashToLiquidate, localToPurchase) = LiquidationHelpers.calculateLocalToPurchase(
            c.factors,
            c.liquidationDiscount,
            fCashLiquidationPV,
            fCashToLiquidate
        );

We should be using fCashLiquidationPV in that call?

[jeffywu]

@T-Woodward please review and confirm: 118b899