Add sanity checks

x/auth/simulation/fake.go

@@ -40,6 +40,10 @@ func SimulateDeductFee(m auth.AccountMapper, f auth.FeeCollectionKeeper) simulat
 			panic(err)
 		}
 		m.SetAccount(ctx, stored)
+		if !coins.IsNotNegative() {
+			panic("setting negative fees")
+		}
+
 		f.AddCollectedFees(ctx, coins)
 
 		event(fmt.Sprintf("auth/SimulateDeductFee/true"))

x/distribution/types/validator_info.go

@@ -45,6 +45,9 @@ func (vi ValidatorDistInfo) TakeFeePoolRewards(fp FeePool, height int64, totalBo
 	blocks := height - vi.FeePoolWithdrawalHeight
 	vi.FeePoolWithdrawalHeight = height
 	accum := vdTokens.MulInt(sdk.NewInt(blocks))
+	if accum.GT(fp.ValAccum.Accum) {
+		panic("individual accum should never be greater than the total")
+	}
 	withdrawalTokens := fp.Pool.MulDec(accum).QuoDec(fp.ValAccum.Accum)
 	remainingTokens := fp.Pool.Minus(withdrawalTokens)