Safe ERC20 permit

contracts/interfaces/IERC2612.sol

@@ -3,12 +3,13 @@
 pragma solidity ^0.8.35;
 
 import { _IERC2612 } from './_IERC2612.sol';
+import { IERC20 } from './IERC20.sol';
 
 /**
  * @title ERC2612 interface
  * @dev see https://eips.ethereum.org/EIPS/eip-2612.
  */
-interface IERC2612 is _IERC2612 {
+interface IERC2612 is _IERC2612, IERC20 {
     /**
      * @notice return the EIP-712 domain separator unique to contract and chain
      * @return domainSeparator domain separator

contracts/interfaces/_IERC2612.sol

@@ -2,4 +2,6 @@
 
 pragma solidity ^0.8.35;
 
-interface _IERC2612 {}
+import { _IERC20 } from './_IERC20.sol';
+
+interface _IERC2612 is _IERC20 {}

contracts/token/fungible/permit/FungibleTokenPermit.sol

@@ -4,6 +4,8 @@ pragma solidity ^0.8.35;
 
 import { IERC2612 } from '../../../interfaces/IERC2612.sol';
 import { IERC5267 } from '../../../interfaces/IERC5267.sol';
+import { FungibleTokenMetadata } from '../metadata/FungibleTokenMetadata.sol';
+import { FungibleToken } from '../FungibleToken.sol';
 import { _FungibleTokenPermit } from './_FungibleTokenPermit.sol';
 import { IFungibleTokenPermit } from './IFungibleTokenPermit.sol';
 
@@ -12,7 +14,9 @@ import { IFungibleTokenPermit } from './IFungibleTokenPermit.sol';
  */
 abstract contract FungibleTokenPermit is
     IFungibleTokenPermit,
-    _FungibleTokenPermit
+    _FungibleTokenPermit,
+    FungibleToken,
+    FungibleTokenMetadata
 {
     /**
      * @inheritdoc IERC2612

contracts/token/fungible/permit/IFungibleTokenPermit.sol

@@ -4,6 +4,14 @@ pragma solidity ^0.8.35;
 
 import { IERC2612 } from '../../../interfaces/IERC2612.sol';
 import { IERC5267 } from '../../../interfaces/IERC5267.sol';
+import { IFungibleTokenMetadata } from '../metadata/IFungibleTokenMetadata.sol';
+import { IFungibleToken } from '../IFungibleToken.sol';
 import { _IFungibleTokenPermit } from './_IFungibleTokenPermit.sol';
 
-interface IFungibleTokenPermit is _IFungibleTokenPermit, IERC2612, IERC5267 {}
+interface IFungibleTokenPermit is
+    _IFungibleTokenPermit,
+    IFungibleToken,
+    IFungibleTokenMetadata,
+    IERC2612,
+    IERC5267
+{}

contracts/utils/SafeERC20.sol

@@ -3,6 +3,7 @@
 pragma solidity ^0.8.35;
 
 import { IERC20 } from '../interfaces/IERC20.sol';
+import { IERC2612 } from '../interfaces/IERC2612.sol';
 import { Address } from './Address.sol';
 
 /**
@@ -15,6 +16,7 @@ library SafeERC20 {
     error SafeERC20__ApproveFromNonZeroToNonZero();
     error SafeERC20__DecreaseAllowanceBelowZero();
     error SafeERC20__OperationFailed();
+    error SafeERC20__PermitFailed();
 
     function safeTransfer(IERC20 token, address to, uint256 value) internal {
         _callOptionalReturn(
@@ -83,6 +85,50 @@ library SafeERC20 {
         }
     }
 
+    /**
+     * @notice approve spender to transfer tokens held by owner via ERC-2612 permit signature
+     * @dev tolerates reverts so that a front-run or already-executed permit does not block
+     * the caller. If the permit call reverts, execution continues only if the existing
+     * allowance equals the permitted value.
+     * @param token ERC-2612 permit token interface
+     * @param owner holder of tokens and signer of permit
+     * @param spender beneficiary of approval
+     * @param value quantity of tokens to approve
+     * @param deadline timestamp after which permit is invalid
+     * @param v secp256k1 'v' value
+     * @param r secp256k1 'r' value
+     * @param s secp256k1 's' value
+     */
+    function safePermit(
+        IERC2612 token,
+        address owner,
+        address spender,
+        uint256 value,
+        uint256 deadline,
+        uint8 v,
+        bytes32 r,
+        bytes32 s
+    ) internal {
+        (bool success, ) = address(token).call(
+            abi.encodeWithSelector(
+                token.permit.selector,
+                owner,
+                spender,
+                value,
+                deadline,
+                v,
+                r,
+                s
+            )
+        );
+
+        // permit authorizes an exact amount; if the call reverted, the existing
+        // allowance must equal the signed value for the permit to be considered
+        // already executed (e.g., via front-running)
+        if (!success && token.allowance(owner, spender) != value)
+            revert SafeERC20__PermitFailed();
+    }
+
     /**
      * @notice send transaction data and check validity of return value, if present
      * @param token ERC20 token interface

test/utils/SafeERC20.ts

@@ -0,0 +1,254 @@
+import { SignerWithAddress } from '@nomicfoundation/hardhat-ethers/signers';
+import { deployMockContract } from '@solidstate/library';
+import { $SafeERC20, $SafeERC20__factory } from '@solidstate/typechain-types';
+import { expect } from 'chai';
+import { ethers } from 'hardhat';
+
+describe('SafeERC20', () => {
+  let instance: $SafeERC20;
+  let deployer: SignerWithAddress;
+  let receiver: SignerWithAddress;
+  let spender: SignerWithAddress;
+
+  beforeEach(async () => {
+    [deployer, receiver, spender] = await ethers.getSigners();
+    instance = await new $SafeERC20__factory(deployer).deploy();
+  });
+
+  describe('#safeTransfer', () => {
+    it('transfers tokens', async () => {
+      const mock = await deployMockContract(deployer, [
+        'function transfer(address,uint256) external returns (bool)',
+      ]);
+
+      await mock.mock.transfer.withArgs(receiver.address, 1n).returns(true);
+
+      await expect(instance.$safeTransfer(mock.address, receiver.address, 1n))
+        .not.to.be.reverted;
+    });
+
+    describe('reverts if', () => {
+      it('transfer returns false', async () => {
+        const mock = await deployMockContract(deployer, [
+          'function transfer(address,uint256) external returns (bool)',
+        ]);
+
+        await mock.mock.transfer.withArgs(receiver.address, 1n).returns(false);
+
+        await expect(
+          instance.$safeTransfer(mock.address, receiver.address, 1n),
+        ).to.be.revertedWithCustomError(instance, 'SafeERC20__OperationFailed');
+      });
+
+      it('transfer reverts', async () => {
+        const mock = await deployMockContract(deployer, [
+          'function transfer(address,uint256) external returns (bool)',
+        ]);
+
+        await mock.mock.transfer
+          .withArgs(receiver.address, 1n)
+          .revertsWithReason('TRANSFER_FAILED');
+
+        await expect(
+          instance.$safeTransfer(mock.address, receiver.address, 1n),
+        ).to.be.revertedWith('TRANSFER_FAILED');
+      });
+    });
+  });
+
+  describe('#safeTransferFrom', () => {
+    it('transfers tokens', async () => {
+      const mock = await deployMockContract(deployer, [
+        'function transferFrom(address,address,uint256) external returns (bool)',
+      ]);
+
+      await mock.mock.transferFrom
+        .withArgs(deployer.address, receiver.address, 1n)
+        .returns(true);
+
+      await expect(
+        instance.$safeTransferFrom(
+          mock.address,
+          deployer.address,
+          receiver.address,
+          1n,
+        ),
+      ).not.to.be.reverted;
+    });
+
+    describe('reverts if', () => {
+      it('transferFrom returns false', async () => {
+        const mock = await deployMockContract(deployer, [
+          'function transferFrom(address,address,uint256) external returns (bool)',
+        ]);
+
+        await mock.mock.transferFrom
+          .withArgs(deployer.address, receiver.address, 1n)
+          .returns(false);
+
+        await expect(
+          instance.$safeTransferFrom(
+            mock.address,
+            deployer.address,
+            receiver.address,
+            1n,
+          ),
+        ).to.be.revertedWithCustomError(instance, 'SafeERC20__OperationFailed');
+      });
+
+      it('transferFrom reverts', async () => {
+        const mock = await deployMockContract(deployer, [
+          'function transferFrom(address,address,uint256) external returns (bool)',
+        ]);
+
+        await mock.mock.transferFrom
+          .withArgs(deployer.address, receiver.address, 1n)
+          .revertsWithReason('TRANSFER_FROM_FAILED');
+
+        await expect(
+          instance.$safeTransferFrom(
+            mock.address,
+            deployer.address,
+            receiver.address,
+            1n,
+          ),
+        ).to.be.revertedWith('TRANSFER_FROM_FAILED');
+      });
+    });
+  });
+
+  describe('#safeApprove', () => {
+    it('approves spender', async () => {
+      const mock = await deployMockContract(deployer, [
+        'function approve(address,uint256) external returns (bool)',
+      ]);
+
+      await mock.mock.approve.withArgs(spender.address, 1n).returns(true);
+
+      await expect(instance.$safeApprove(mock.address, spender.address, 1n)).not
+        .to.be.reverted;
+    });
+
+    describe('reverts if', () => {
+      it('approve returns false', async () => {
+        const mock = await deployMockContract(deployer, [
+          'function approve(address,uint256) external returns (bool)',
+        ]);
+
+        await mock.mock.approve.withArgs(spender.address, 1n).returns(false);
+
+        await expect(
+          instance.$safeApprove(mock.address, spender.address, 1n),
+        ).to.be.revertedWithCustomError(instance, 'SafeERC20__OperationFailed');
+      });
+    });
+  });
+
+  describe('#safeIncreaseAllowance', () => {
+    it('todo');
+  });
+
+  describe('#safeDecreaseAllowance', () => {
+    it('todo');
+  });
+
+  describe('#safePermit', () => {
+    it('executes permit', async () => {
+      const mock = await deployMockContract(deployer, [
+        'function permit(address,address,uint256,uint256,uint8,bytes32,bytes32) external',
+      ]);
+
+      await mock.mock.permit.returns();
+
+      await expect(
+        instance.$safePermit(
+          mock.address,
+          deployer.address,
+          spender.address,
+          1n,
+          ethers.MaxUint256,
+          27,
+          ethers.ZeroHash,
+          ethers.ZeroHash,
+        ),
+      ).not.to.be.reverted;
+    });
+
+    it('tolerates front-run', async () => {
+      const mock = await deployMockContract(deployer, [
+        'function permit(address,address,uint256,uint256,uint8,bytes32,bytes32) external',
+        'function allowance(address,address) external view returns (uint256)',
+      ]);
+
+      await mock.mock.permit.reverts();
+      await mock.mock.allowance
+        .withArgs(deployer.address, spender.address)
+        .returns(1n);
+
+      await expect(
+        instance.$safePermit(
+          mock.address,
+          deployer.address,
+          spender.address,
+          1n,
+          ethers.MaxUint256,
+          27,
+          ethers.ZeroHash,
+          ethers.ZeroHash,
+        ),
+      ).not.to.be.reverted;
+    });
+
+    describe('reverts if', () => {
+      it('permit fails and allowance is insufficient', async () => {
+        const mock = await deployMockContract(deployer, [
+          'function permit(address,address,uint256,uint256,uint8,bytes32,bytes32) external',
+          'function allowance(address,address) external view returns (uint256)',
+        ]);
+
+        await mock.mock.permit.reverts();
+        await mock.mock.allowance
+          .withArgs(deployer.address, spender.address)
+          .returns(0n);
+
+        await expect(
+          instance.$safePermit(
+            mock.address,
+            deployer.address,
+            spender.address,
+            1n,
+            ethers.MaxUint256,
+            27,
+            ethers.ZeroHash,
+            ethers.ZeroHash,
+          ),
+        ).to.be.revertedWithCustomError(instance, 'SafeERC20__PermitFailed');
+      });
+
+      it('permit fails and allowance is excessive', async () => {
+        const mock = await deployMockContract(deployer, [
+          'function permit(address,address,uint256,uint256,uint8,bytes32,bytes32) external',
+          'function allowance(address,address) external view returns (uint256)',
+        ]);
+
+        await mock.mock.permit.reverts();
+        await mock.mock.allowance
+          .withArgs(deployer.address, spender.address)
+          .returns(2n);
+
+        await expect(
+          instance.$safePermit(
+            mock.address,
+            deployer.address,
+            spender.address,
+            1n,
+            ethers.MaxUint256,
+            27,
+            ethers.ZeroHash,
+            ethers.ZeroHash,
+          ),
+        ).to.be.revertedWithCustomError(instance, 'SafeERC20__PermitFailed');
+      });
+    });
+  });
+});