Yul Optimizer Call Graph Fix

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.37;

/// @notice Demonstrates that the Yul optimizer now correctly handles mutually recursive functions.
/// The contract compiles and runs on 0.8.37, which includes the 0.8.36 fix.
contract Main {
    /// @dev Recursively computes the factorial of `n` using two mutually recursive functions.
    function fact(uint256 n) public pure returns (uint256) {
        return _factHelper(n);
    }

    /// @dev Helper that calls the other helper to illustrate recursion.
    function _factHelper(uint256 n) internal pure returns (uint256) {
        if (n == 0) return 1;
        return _factHelper2(n - 1) * n;
    }

    /// @dev Second helper that calls the first helper.
    function _factHelper2(uint256 n) internal pure returns (uint256) {
        if (n == 0) return 1;
        return _factHelper(n - 1) * n;
    }
}

Tests

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.37;
import "./main.sol";

contract MainTest {
    Main main;

    constructor() {
        main = new Main();
    }

    function test_factZero() public {
        require(main.fact(0) == 1, "fact(0) should be 1");
    }

    function test_factFive() public {
        require(main.fact(5) == 120, "fact(5) should be 120");
    }
}