Wrapped fCash (wfCash) is a compatibility layer for developers who want to integrate with Notional lending but unable to use fCash's native ERC1155 specification. wfCash is compatible with ERC20 and ERC4626.
Technical Walkthrough: https://www.youtube.com/watch?v=RvCYFR2Yjls
Audits: TBD
Each wfCash contract is deployed from the WrappedfCashFactory using a CREATE2 opcode and parameterized by a currency id and a maturity. Currency IDs are autoincrementing IDs generated by the Notional contract and correspond to a currency (i.e. ETH, DAI, USDC, etc) that can be lent and borrowed on Notional.
The maturity the unix timestamp of the block time when the fCash will mature (and convert to it accruing money market interest).
One canonical wfCash contract can be deployed permissionlessly for every currencyId and maturity combination through the WrappedfCashFactory. Each wfCash contract is a OpenZeppelin BeaconProxy that refers to a single BeaconImplementation of the wfCashERC4626 contract.
Lending fCash can be done by calling mintViaUnderlying, mint or deposit. ERC4626 is provided as a compatibility layer but due to the computation required it is not the most gas efficient implementation. Using the non-ERC4626 mintViaUnderlying function is significantly more gas efficient. (See table below).
Creating wfCash tokens can also be done by using an ERC1155 safeTransferFrom to the corresponding wfCash contract from the main Notional contract. This allows accounts to seamlessly enter and exit wfCash positions from Notional ERC1155.
Caveat: Notional ERC1155 fCash can be used as collateral for borrowing. However, wfCash cannot be used in this way since it is held in escrow by the wfCash contract. This should not be a limitation for lend-only accounts.
wfCash can be redeemed anytime before or after maturity. Redeeming fCash prior to maturity means selling it on Notional for underlying (i.e. USDC, DAI, etc). Selling fCash is subject to prevailing market interest rates and therefore does not guarantee that the holder will receive their promised fixed interest.
fCash (and wfCash is no different) settles to prime cash tokens (i.e. pCash) at maturity and will accrue a variable interest rate from that point forward. Accounts that redeem their wfCash after maturity will receive their fixed interest as well as any accrued variable rate interest post maturity.
Before or after maturity, redeeming wfCash can be done by calling redeem, redeemToUnderlying, or withdraw. Accounts are also able to call redeem and specify the transferfCash boolean in RedeemOpts to have the wfCash transfer the ERC1155 fCash token to their Notional account.
fCash experiences liquidity constraints at extremely low and extremely high fixed rates. At fixed interest rates near zero, there is insufficient fCash in the corresponding liquidity pool to be purchased. On Notional, lending will revert in these conditions. However, wfCash will continue to allow lenders to mint wfCash at a 0% interest rate (i.e. at a 1-1 exchange rate with underlying). This fixed rate is disadvantageous to the user because they forgo any accrued variable interest in favor of 0% fixed interest. However, as a compatibility layer it may be useful in some contexts to ensure that wfCash will can continue to mint shares even under these conditions.
When lending at zero interest rates occurs, the wfCash contract will take underlying tokens and hold them as Prime Cash. If a user redeems their fCash prior to maturity, they will receive as much underlying as the corresponding amount of fCash could be sold for on the fCash market. If the contract does not have sufficient actual fCash to sell to the market, any shortfall is deducted from the prime cash balance. Since fCash always trades at a discount, the wrapper contract will always accrue some profit due to the foregone variable lending interest under these conditions.
In Notional V3, asset tokens are deprecated in favor of Prime Cash. The mintViaAsset and redeemViaAsset methods are deprecated. Minting and redeeming to prime cash is not supported.
| WrappedfCashFactory contract | |||||
|---|---|---|---|---|---|
| Function Name | min | avg | median | max | # calls |
| computeAddress | 11074 | 11074 | 11074 | 11074 | 2 |
| deployWrapper | 884 | 407889 | 431750 | 450250 | 56 |
| wfCash ERC4626 contract | |||||
|---|---|---|---|---|---|
| Function Name | min | avg | median | max | # calls |
| allowance | 763 | 763 | 763 | 763 | 2 |
| approve | 24641 | 24641 | 24641 | 24641 | 2 |
| asset | 13235 | 28812 | 30746 | 30746 | 272 |
| balanceOf | 686 | 1311 | 686 | 2686 | 467 |
| convertToAssets | 25059 | 44773 | 45441 | 80861 | 8 |
| convertToShares | 25076 | 49871 | 45458 | 121531 | 8 |
| deposit | 25428 | 313464 | 295482 | 527192 | 39 |
| getBalances | 19898 | 46370 | 47898 | 74700 | 106 |
| getCurrencyId | 489 | 1385 | 489 | 2489 | 203 |
| getMaturity | 463 | 463 | 463 | 463 | 136 |
| getTotalFCashAvailable | 21124 | 56066 | 61931 | 77476 | 18 |
| getUnderlyingToken | 17055 | 17055 | 17055 | 17055 | 90 |
| getfCashId | 401 | 890 | 401 | 2401 | 368 |
| hasMatured | 555 | 555 | 555 | 555 | 41 |
| initialize | 43204 | 150418 | 161394 | 178984 | 55 |
| maxRedeem | 2720 | 2720 | 2720 | 2720 | 42 |
| maxWithdraw | 40132 | 53871 | 53106 | 77969 | 45 |
| mint | 25363 | 293675 | 281686 | 484406 | 110 |
| onERC1155Received | 23246 | 45908 | 36489 | 97089 | 49 |
| previewDeposit | 83117 | 90593 | 83432 | 140469 | 36 |
| previewMint | 78582 | 81241 | 78750 | 122054 | 34 |
| previewRedeem | 37852 | 48112 | 50723 | 75591 | 39 |
| previewWithdraw | 25350 | 53423 | 59142 | 84076 | 44 |
| recoverInvalidfCash | 1934 | 45966 | 45966 | 89998 | 2 |
| redeem(uint256,(bool,bool,address,uint32)) | 3288 | 119037 | 115795 | 225510 | 32 |
| redeem(uint256,address,address)(uint256) | 15231 | 214588 | 269493 | 323160 | 45 |
| totalAssets | 44951 | 55591 | 55451 | 89560 | 92 |
| totalSupply | 426 | 2316 | 2426 | 2426 | 238 |
| withdraw | 63328 | 284460 | 315572 | 395806 | 47 |