flash-mint-token

An ERC-20 with ERC-3156 flash minting and a bounded fee. A borrower can mint up to maxFlashLoan of the token inside one transaction; after its onFlashLoan callback runs, the minted amount is burned and a bounded fee is pulled to a treasury — all atomically. Net total supply is unchanged by any flash loan. MIT.

Flash mint vs flash loan

A pool-based flash loan lends out existing liquidity, so its ceiling is the pool size. A flash mint creates the liquidity on demand and destroys it in the same tx — so the ceiling is type(uint256).max − totalSupply, and there is no pool to drain. Useful for closing an arbitrage or refinancing a position without fronting capital.

Mechanics

• flashLoan(receiver, token, amount, data) (ERC-3156): mints amount to receiver, calls receiver.onFlashLoan(...), then requires receiver to have approved this contract for amount + fee and burns amount + transfers fee to the treasury. receiver must return the ERC-3156 magic value.
• flashFee(token, amount) = amount * flashFeeBps / 1e4, with flashFeeBps hard-capped at 10%.
• The fee is paid from the borrower's real balance (the minted amount is burned), so a profitable flash mint must actually earn at least the fee.
• Owner can mint circulating supply, setFlashFeeBps (≤ cap), and setTreasury (non-zero). No admin path to holder balances.

Invariant (fuzzed, fail_on_revert=true, non-hollow)

• Supply conservation — totalSupply always equals the ghost sum of owner mints, across any sequence of flash loans (any size, any fee, including nested/re-entrant loans). Flash loans mint-then- burn net-zero; fees only move existing tokens. 12,800 calls, 0 reverts. Mutation-checked (zeroing the fee fails the fee tests).

Notes (honest)

• Nested/re-entrant flash loans are allowed by design (each is self-balancing); supply stays conserved — tested.
• The token is a plain ERC-20 otherwise (no rebasing/hooks). Unaudited reference implementation.

forge test   # 15 tests: happy path, fee, maxFlashLoan, nested loans, revert paths, admin, supply invariant