feat(contracts): add wrapped HypERC4626 for ease of defi use (#4563)

### Description

### Drive-by changes

None

### Related issues

- closes https://github.com/chainlight-io/2024-08-hyperlane/issues/7

### Backward compatibility

Yes

### Testing

Unit

.changeset/itchy-bananas-know.md

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+---
+'@hyperlane-xyz/core': patch
+---
+
+Add wrapped HypERC4626 for easy defi use

.changeset/shiny-baboons-hunt.md

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+---
+'@hyperlane-xyz/core': minor
+---
+
+Added WHypERC4626 as a wrapper for rebasing HypERC4626

solidity/contracts/token/extensions/WHypERC4626.sol

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+// SPDX-License-Identifier: MIT OR Apache-2.0
+pragma solidity >=0.8.0;
+
+import {ERC20} from "@openzeppelin/contracts/token/ERC20/ERC20.sol";
+import {HypERC4626} from "./HypERC4626.sol";
+import {PackageVersioned} from "../../PackageVersioned.sol";
+
+/*@@@@@@@       @@@@@@@@@
+ @@@@@@@@@       @@@@@@@@@
+  @@@@@@@@@       @@@@@@@@@
+   @@@@@@@@@       @@@@@@@@@
+    @@@@@@@@@@@@@@@@@@@@@@@@@
+     @@@@@  HYPERLANE  @@@@@@@
+    @@@@@@@@@@@@@@@@@@@@@@@@@
+   @@@@@@@@@       @@@@@@@@@
+  @@@@@@@@@       @@@@@@@@@
+ @@@@@@@@@       @@@@@@@@@
+@@@@@@@@@       @@@@@@@@*/
+
+/**
+ * @title WHypERC4626
+ * @author Abacus Works
+ * @notice A wrapper for HypERC4626 that allows for wrapping and unwrapping of underlying rebasing tokens
+ */
+contract WHypERC4626 is ERC20, PackageVersioned {
+    HypERC4626 public immutable underlying;
+
+    constructor(
+        HypERC4626 _underlying,
+        string memory name,
+        string memory symbol
+    ) ERC20(name, symbol) {
+        underlying = _underlying;
+    }
+
+    /*
+     * @notice Wraps an amount of underlying tokens into wrapped tokens
+     * @param _underlyingAmount The amount of underlying tokens to wrap
+     * @return The amount of wrapped tokens
+     */
+    function wrap(uint256 _underlyingAmount) external returns (uint256) {
+        require(
+            _underlyingAmount > 0,
+            "WHypERC4626: wrap amount must be greater than 0"
+        );
+        uint256 wrappedAmount = underlying.assetsToShares(_underlyingAmount);
+        _mint(msg.sender, wrappedAmount);
+        underlying.transferFrom(msg.sender, address(this), _underlyingAmount);
+        return wrappedAmount;
+    }
+
+    /*
+     * @notice Unwraps an amount of wrapped tokens into underlying tokens
+     * @param _wrappedAmount The amount of wrapped tokens to unwrap
+     * @return The amount of underlying tokens
+     */
+    function unwrap(uint256 _wrappedAmount) external returns (uint256) {
+        require(
+            _wrappedAmount > 0,
+            "WHypERC4626: unwrap amount must be greater than 0"
+        );
+        uint256 underlyingAmount = underlying.sharesToAssets(_wrappedAmount);
+        _burn(msg.sender, _wrappedAmount);
+        underlying.transfer(msg.sender, underlyingAmount);
+        return underlyingAmount;
+    }
+
+    /*
+     * @notice Gets the amount of wrapped tokens for a given amount of underlying tokens
+     * @param _underlyingAmount The amount of underlying tokens
+     * @return The amount of wrapped tokens
+     */
+    function getWrappedAmount(
+        uint256 _underlyingAmount
+    ) external view returns (uint256) {
+        return underlying.assetsToShares(_underlyingAmount);
+    }
+
+    /*
+     * @notice Gets the amount of underlying tokens for a given amount of wrapped tokens
+     * @param _wrappedAmount The amount of wrapped tokens
+     * @return The amount of underlying tokens
+     */
+    function getUnderlyingAmount(
+        uint256 _wrappedAmount
+    ) external view returns (uint256) {
+        return underlying.sharesToAssets(_wrappedAmount);
+    }
+
+    /*
+     * @notice Gets the amount of wrapped tokens for 1 unit of underlying tokens
+     * @return The amount of wrapped tokens
+     */
+    function wrappedPerUnderlying() external view returns (uint256) {
+        return underlying.assetsToShares(1 * 10 ** underlying.decimals());
+    }
+
+    /*
+     * @notice Gets the amount of underlying tokens for 1 unit of wrapped tokens
+     * @return The amount of underlying tokens
+     */
+    function underlyingPerWrapped() external view returns (uint256) {
+        return underlying.sharesToAssets(1 * 10 ** decimals());
+    }
+
+    /*
+     * @notice Gets the decimals of the wrapped token
+     * @return The decimals of the wrapped token
+     */
+    function decimals() public view override returns (uint8) {
+        return underlying.decimals();
+    }
+}

solidity/test/token/WHypERC4626.t.sol

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+// SPDX-License-Identifier: MIT OR Apache-2.0
+pragma solidity ^0.8.13;
+
+import {Test} from "forge-std/Test.sol";
+import {MockMailbox} from "../../contracts/mock/MockMailbox.sol";
+import {WHypERC4626} from "../../contracts/token/extensions/WHypERC4626.sol";
+import {HypERC4626} from "../../contracts/token/extensions/HypERC4626.sol";
+import {ERC20} from "@openzeppelin/contracts/token/ERC20/ERC20.sol";
+
+contract MockHypERC4626 is HypERC4626 {
+    constructor(address _mailbox) HypERC4626(18, _mailbox, 2) {}
+
+    function mint(address to, uint256 amount) external {
+        _mint(to, amount);
+    }
+}
+
+contract WHypERC4626Test is Test {
+    WHypERC4626 public wHypERC4626;
+    MockHypERC4626 public underlyingToken;
+    address public alice = address(0x1);
+    address public bob = address(0x2);
+
+    function setUp() public {
+        MockMailbox mailbox = new MockMailbox(1);
+        underlyingToken = new MockHypERC4626(address(mailbox));
+        wHypERC4626 = new WHypERC4626(
+            underlyingToken,
+            "Wrapped Rebasing Token",
+            "WRT"
+        );
+
+        underlyingToken.mint(alice, 1000 * 10 ** 18);
+        underlyingToken.mint(bob, 1000 * 10 ** 18);
+    }
+
+    function test_wrap() public {
+        uint256 amount = 100 * 10 ** 18;
+
+        vm.startPrank(alice);
+        underlyingToken.approve(address(wHypERC4626), amount);
+        uint256 wrappedAmount = wHypERC4626.wrap(amount);
+
+        assertEq(wHypERC4626.balanceOf(alice), wrappedAmount);
+        assertEq(underlyingToken.balanceOf(alice), 900 * 10 ** 18);
+        vm.stopPrank();
+    }
+
+    function test_wrap_revertsWhen_zeroAmount() public {
+        vm.startPrank(alice);
+        underlyingToken.approve(address(wHypERC4626), 0);
+        vm.expectRevert("WHypERC4626: wrap amount must be greater than 0");
+        wHypERC4626.wrap(0);
+        vm.stopPrank();
+    }
+
+    function test_unwrap() public {
+        uint256 amount = 100 * 10 ** 18;
+
+        vm.startPrank(alice);
+        underlyingToken.approve(address(wHypERC4626), amount);
+        uint256 wrappedAmount = wHypERC4626.wrap(amount);
+
+        uint256 unwrappedAmount = wHypERC4626.unwrap(wrappedAmount);
+
+        assertEq(wHypERC4626.balanceOf(alice), 0);
+        assertEq(underlyingToken.balanceOf(alice), 1000 * 10 ** 18);
+        assertEq(unwrappedAmount, amount);
+        vm.stopPrank();
+    }
+
+    function test_unwrap_revertsWhen_zeroAmount() public {
+        vm.startPrank(alice);
+        vm.expectRevert("WHypERC4626: unwrap amount must be greater than 0");
+        wHypERC4626.unwrap(0);
+        vm.stopPrank();
+    }
+
+    function test_getWrappedAmount() public view {
+        uint256 amount = 100 * 10 ** 18;
+        uint256 wrappedAmount = wHypERC4626.getWrappedAmount(amount);
+
+        assertEq(wrappedAmount, underlyingToken.assetsToShares(amount));
+    }
+
+    function test_getUnderlyingAmount() public view {
+        uint256 amount = 100 * 10 ** 18;
+        uint256 underlyingAmount = wHypERC4626.getUnderlyingAmount(amount);
+
+        assertEq(underlyingAmount, underlyingToken.sharesToAssets(amount));
+    }
+
+    function test_wrappedPerUnderlying() public view {
+        uint256 wrappedPerUnderlying = wHypERC4626.wrappedPerUnderlying();
+
+        assertEq(
+            wrappedPerUnderlying,
+            underlyingToken.assetsToShares(1 * 10 ** underlyingToken.decimals())
+        );
+    }
+
+    function test_underlyingPerWrapped() public view {
+        uint256 underlyingPerWrapped = wHypERC4626.underlyingPerWrapped();
+
+        assertEq(
+            underlyingPerWrapped,
+            underlyingToken.sharesToAssets(1 * 10 ** underlyingToken.decimals())
+        );
+    }
+
+    function test_decimals() public view {
+        uint8 decimals = wHypERC4626.decimals();
+
+        assertEq(decimals, underlyingToken.decimals());
+    }
+}