Add ERC20-compatible Escape Hatch to Gem Join Contracts

[hexonaut]

It's a common pattern to include an ERC20 token extraction mechanism in rapidly developed contracts in case of accidentally trapped funds. I think it could be useful to upgrade all the gem join contracts to be compliant with part of the ERC20 standard - specifically transfer, transferFrom and balanceOf. This would basically provide an ERC20-compliant escape hatch for accidentally stuck collateral to be extracted from Maker.

The functions would look something like this (pseudocode):

function balanceOf (account) {
	// Return the ink that can be freed from vat.frob (after repaying with the available vat.dai) and any vat.gem available
}

function transfer (address recipient, uint amount) {
	if (vat.gem[ilk][msg.sender] < amount) {
		// Pull the ink out of the cdp and repay as much dai as available
		vat.frob(ilk, msg.sender, msg.sender, msg.sender, -int(sub(amount, vat.gem[ilk][msg.sender])), -int(vat.dai[msg.sender]));
	}

	exit(recipient, amount);
}

function transferFrom (address sender, address recipient, uint amount) {
	require(sender == msg.sender)

	transfer(recipient, amount);
}

This would allow anyone to completely unwind a CDP with only the ERC20 transfer semantics as any account is able to repay debt. So for example to unwind my locked CDP, I can do: Flash Loan (Dai), Repay all CDP Debt, gemJoin.transfer(myAccount, gemJoin.getBalance()), Trade Gem for Dai, Repay Flash Dai Loan.

The only downside I can see to this is a slight increase in code complexity, but we get the added benefit of lower liquidations from trapped funds.

[hexonaut]

Changed my view on this - the code is unnecessary bloat. Closing.