OptimismMintableERC20: Add permit support + native permit2 support

[tynes]

Add permit support to the OptimismMintableERC20 token implementation. This can easily be done using the ERC20Permit contract in openzeppelin. Also add native support for permit2 by enforcing that the allowance for permit2 always returns type(uint256).max.

[marktoda]

• clear requirements, why they need permit + permit2

  • Default support for ERC2612 permits is a pretty clear UX improvement, enabling single tx actions and gas abstraction without native token in wallet to pay for an initial approve
  • Permit2 has become the primary approval mechanism for all Uniswap interface interactions and is integrated by many other DeFi protocols that I'm aware of. Directly integrating tokens with it saves an entire approval step for users, simplifying the user experience of interacting with these protocols. It also synergizes well with intents-based trading systems like UniswapX, where users could submit a trade with a single signature without ever requiring any native token to set up for the trade

• is there precendent for baking permit2 support directly into a token? why/why not? related to prior bullet what does this give vs. normal out-of-token support

  • One I'm aware of is the Pol token

[mds1]

Thanks @marktoda! One follow up: What's the value of standard ERC2612 permit if permit2 is directly integrated? It seems to me permit2 is a superset of permit. I'm ok with adding both—I see POL has both as well—just curious if there's a different use case for permit vs. permit2, or if it's just to give users/devs more options?

[maurelian]

@marktoda can you confirm that we should enable this setting to _givePermit2InfiniteAllowance in the Solady ERC20? Is that a basic requirement to make the ERC20 Permit2 compatible?