Numoen contest - Diana's results

G-01 x += y costs more gas than x = x + y for state variables (same applies for x -= y)

Using the addition operator instead of plus-equals saves 113 gas.

There are 10 instances of this issue

https://github.com/code-423n4/2023-01-numoen/blob/main/src/core/Lendgine.sol

File: src/core/Lendgine.sol

91: totalLiquidityBorrowed += liquidity;
114: totalLiquidityBorrowed -= liquidity;
176: totalPositionSize -= size;
257: rewardPerPositionStored += FullMath.mulDiv(dilutionSpeculative, 1e18, totalPositionSize);

https://github.com/code-423n4/2023-01-numoen/blob/main/src/periphery/LiquidityManager.sol

File: src/periphery/LiquidityManager.sol

178: position.tokensOwed += FullMath.mulDiv(position.size, rewardPerPositionPaid - position.rewardPerPositionPaid, 1e18);
180: position.size += size;
214: position.tokensOwed += FullMath.mulDiv(position.size, rewardPerPositionPaid - position.rewardPerPositionPaid, 1e18);
216: position.size -= params.size;
238: position.tokensOwed += FullMath.mulDiv(position.size, rewardPerPositionPaid - position.rewardPerPositionPaid, 1e18);
242: position.tokensOwed -= amount;

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G-02 Internal functions only called once can be inlined to save gas

Not inlining costs 20 to 40 gas because of two extra JUMP instructions and additional stack operations needed for function calls.

There are 6 instances of this issue

https://github.com/code-423n4/2023-01-numoen/blob/main/src/core/libraries/Position.sol

File: src/core/libraries/Position.sol

69: function newTokensOwed(Position.Info memory position, uint256 rewardPerPosition) internal pure returns (uint256) {
73: function convertLiquidityToPosition(
86: function convertPositionToLiquidity(

https://github.com/code-423n4/2023-01-numoen/blob/main/src/core/libraries/PositionMath.sol

File: src/core/libraries/PositionMath.sol

12: function addDelta(uint256 x, int256 y) internal pure returns (uint256 z) {

https://github.com/code-423n4/2023-01-numoen/blob/main/src/periphery/UniswapV2/libraries/UniswapV2Library.sol

File: src/periphery/UniswapV2/libraries/UniswapV2Library.sol

51: function getAmountOut(
69: function getAmountIn(

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G-03 Not using the named return variables when a function returns, wastes deployment gas

Each MLOAD and MSTORE costs 3 additional gas

There are 3 instances of this issue

https://github.com/code-423n4/2023-01-numoen/blob/main/src/core/JumpRate.sol

File: src/core/JumpRate.sol

13: function getBorrowRate(uint256 borrowedLiquidity, uint256 totalLiquidity) public pure override returns (uint256 rate) {
25: function getSupplyRate(
40: function utilizationRate(uint256 borrowedLiquidity, uint256 totalLiquidity) private pure returns (uint256 rate) {

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G-04 Splitting require() statements that use && saves gas

See this issue which describes the fact that there is a larger deployment gas cost, but with enough runtime calls, the change ends up being cheaper by 3 gas

There are 2 instances of this issue

https://github.com/code-423n4/2023-01-numoen/blob/main/src/periphery/UniswapV2/libraries/UniswapV2Library.sol

File: src/periphery/UniswapV2/libraries/UniswapV2Library.sol

61: require(reserveIn > 0 && reserveOut > 0, "UniswapV2Library: INSUFFICIENT_LIQUIDITY");
79: require(reserveIn > 0 && reserveOut > 0, "UniswapV2Library: INSUFFICIENT_LIQUIDITY");

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G-05 Use a more recent version of solidity

Use a solidity version of at least 0.8.2 to get compiler automatic inlining
Use a solidity version of at least 0.8.3 to get better struct packing and cheaper multiple storage reads
Use a solidity version of at least 0.8.4 to get custom errors, which are cheaper at deployment than revert()/require() strings
Use a solidity version of at least 0.8.10 to have external calls skip contract existence checks if the external call has a return value

There are 15 instances of this issue

https://github.com/code-423n4/2023-01-numoen/blob/main/src/core/libraries/Position.sol

File: src/core/libraries/Position.sol

2: pragma solidity ^0.8.4;

https://github.com/code-423n4/2023-01-numoen/blob/main/src/core/libraries/PositionMath.sol

File: src/core/libraries/PositionMath.sol

2: pragma solidity >=0.5.0;

https://github.com/code-423n4/2023-01-numoen/blob/main/src/core/Factory.sol

File: src/core/Factory.sol

2: pragma solidity ^0.8.4;

https://github.com/code-423n4/2023-01-numoen/blob/main/src/core/ImmutableState.sol

File: src/core/ImmutableState.sol

2: pragma solidity ^0.8.0;

https://github.com/code-423n4/2023-01-numoen/blob/main/src/core/JumpRate.sol

File: src/core/JumpRate.sol

2: pragma solidity ^0.8.0;

https://github.com/code-423n4/2023-01-numoen/blob/main/src/core/Lendgine.sol

File: src/core/Lendgine.sol

2: pragma solidity ^0.8.4;

https://github.com/code-423n4/2023-01-numoen/blob/main/src/core/Pair.sol

File: src/core/Pair.sol

2: pragma solidity ^0.8.4;

https://github.com/code-423n4/2023-01-numoen/blob/main/src/libraries/Balance.sol

File: src/libraries/Balance.sol

2: pragma solidity ^0.8.4;

https://github.com/code-423n4/2023-01-numoen/blob/main/src/libraries/SafeCast.sol

File: src/libraries/SafeCast.sol

2: pragma solidity ^0.8.0;

https://github.com/code-423n4/2023-01-numoen/blob/main/src/periphery/libraries/LendgineAddress.sol

File: src/periphery/libraries/LendgineAddress.sol

2: pragma solidity >=0.5.0;

https://github.com/code-423n4/2023-01-numoen/blob/main/src/periphery/UniswapV2/libraries/UniswapV2Library.sol

File: src/periphery/UniswapV2/libraries/UniswapV2Library.sol

1: pragma solidity >=0.8.0;

https://github.com/code-423n4/2023-01-numoen/blob/main/src/periphery/LendgineRouter.sol

File: src/periphery/LendgineRouter.sol

2: pragma solidity ^0.8.4;

https://github.com/code-423n4/2023-01-numoen/blob/main/src/periphery/LiquidityManager.sol

File: src/periphery/LiquidityManager.sol

2: pragma solidity ^0.8.4;

https://github.com/code-423n4/2023-01-numoen/blob/main/src/periphery/Payment.sol

File: src/periphery/Payment.sol

2: pragma solidity ^0.8.4;

https://github.com/code-423n4/2023-01-numoen/blob/main/src/periphery/SwapHelper.sol

File: src/periphery/SwapHelper.sol

2: pragma solidity ^0.8.4;

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G-06 Duplicated require() or revert() checks should be refactored to a modifier or function

Saves deployment costs.

There are 2 instances of this issue

https://github.com/code-423n4/2023-01-numoen/blob/main/src/periphery/UniswapV2/libraries/UniswapV2Library.sol

File: src/periphery/UniswapV2/libraries/UniswapV2Library.sol

61: require(reserveIn > 0 && reserveOut > 0, "UniswapV2Library: INSUFFICIENT_LIQUIDITY");
79: require(reserveIn > 0 && reserveOut > 0, "UniswapV2Library: INSUFFICIENT_LIQUIDITY");

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