✨ add toUint256(int256) to SafeCastLib

[0xClandestine]

Noticed both are missing:

Thinking we would check that each param is greater than zero:

function toUint256(int256 x) internal pure returns (uint256) {
    if (x < 0) revert FailedConversion();
    return uint256(x);
}

[0xClandestine]

Wouldn't hurt to add complementWad as well:

function complementWad(uint256 x) internal pure returns (uint256 result) {
    assembly {
        result := mul(lt(x, WAD), sub(WAD, x))
    }
}

[0xClandestine]

powWad(uint256, uint256) could also be added to FixedPointMathLib

[Vectorized]

I think let's leave it as powWad(int256 x, int256 y).

[0xClandestine]

@Vectorized All of this is inspired by Balancer v2 arithmetic:

Complement reference:
https://github.com/balancer/balancer-v2-monorepo/blob/bc3b3fee6e13e01d2efe610ed8118fdb74dfc1f2/pkg/solidity-utils/contracts/math/FixedPoint.sol#L156

Furthermore, for powWad we only need to ensure that the signed integers (params) are greater than zero. Although my main issue is with the return value, which requires me to check that result > 0. So tbh its not a huge issue.

[0xClandestine]

I think let's leave it as powWad(int256 x, int256 y).

powWad(int256, int256) -> (uint256) could be a happy median

[Vectorized]

I think I'll let the people who need powWad and wadComplement copy paste from balancer.

Licensing issue, and high risk of edge cases unaccounted for.