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Fix remaining dust on oToken when burning all #1672

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Fix remaining dust on oToken when burning all #1672

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23 changes: 12 additions & 11 deletions contracts/contracts/token/OUSD.sol
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Original file line number Diff line number Diff line change
Expand Up @@ -404,31 +404,32 @@ contract OUSD is Initializable, InitializableERC20Detailed, Governable {
}

bool isNonRebasingAccount = _isNonRebasingAccount(_account);
// creditAmount is rounded down, so may remove fewer credits
uint256 creditAmount = _amount.mulTruncate(_creditsPerToken(_account));
uint256 currentCredits = _creditBalances[_account];

// Remove the credits, burning rounding errors
if (
currentCredits == creditAmount || currentCredits - 1 == creditAmount
) {
// Handle dust from rounding

if (_amount == balanceOf(_account)) {
// Remove all account credits, burning rounding dust
_creditBalances[_account] = 0;
} else if (currentCredits > creditAmount) {
_creditBalances[_account] = _creditBalances[_account].sub(
creditAmount
);
_creditBalances[_account] -= creditAmount;
} else {
revert("Remove exceeds balance");
}

// Remove from the credit tallies and non-rebasing supply
if (isNonRebasingAccount) {
nonRebasingSupply = nonRebasingSupply.sub(_amount);
nonRebasingSupply -= _amount;
} else {
_rebasingCredits = _rebasingCredits.sub(creditAmount);
// Given that creditAmount could be rounded down, this could leave
// the contract with slightly more rebasing credits. This is the
// best side to round to, since this slows rebasing rather than
// speed it up
_rebasingCredits -= creditAmount;
}

_totalSupply = _totalSupply.sub(_amount);
_totalSupply -= _amount;

emit Transfer(_account, address(0), _amount);
}
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4 changes: 1 addition & 3 deletions contracts/test/vault/redeem.js
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Original file line number Diff line number Diff line change
Expand Up @@ -431,9 +431,7 @@ describe("Vault Redeem", function () {
await dai.connect(anna).approve(vault.address, newDaiBalance);
await vault.connect(anna).mint(dai.address, newDaiBalance, 0);
await vault.connect(anna).redeemAll(0);
// FIXME - this is failing as a balance of 1 is being returned instead of 0
// Tracking issue https://github.com/OriginProtocol/origin-dollar/issues/1495
// await expect(anna).has.a.balanceOf("0.00", ousd);
await expect(anna).has.a.balanceOf("0.00", ousd);
});

it("Should respect minimum unit amount argument in redeem", async () => {
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