Subtraction can be done unchecked because the require statement checks for underflow

[code423n4]

Handle

GiveMeTestEther

Vulnerability details

Impact

On the L388/L429/L464 (only subtraction)/L508 there is a subtraction than can be done unchecked because the require statement above those line checks for underflow.

Therefore those lines can be put in an unchecked {} block to save gas.

Proof of Concept

Example for L388:
require(newBal < type(uint112).max && newBal > prevBal, "erc");
amount = uint112(newBal - prevBal);

First part of the require statement checks for safe downcasting and the second part for underflow. Therefore we can write:
unchecked { amount = uint112(newBal - prevBal); }

https://github.com/code-423n4/2021-11-streaming/blob/56d81204a00fc949d29ddd277169690318b36821/Streaming/src/Locke.sol#L388

https://github.com/code-423n4/2021-11-streaming/blob/56d81204a00fc949d29ddd277169690318b36821/Streaming/src/Locke.sol#L429

https://github.com/code-423n4/2021-11-streaming/blob/56d81204a00fc949d29ddd277169690318b36821/Streaming/src/Locke.sol#L464

https://github.com/code-423n4/2021-11-streaming/blob/56d81204a00fc949d29ddd277169690318b36821/Streaming/src/Locke.sol#L508

Tools Used

Recommended Mitigation Steps

• put L388/L429/L464 un an unchecked {} block