docs(chisel): document uint256 cast quirk of abi.encode(1-2) causing wrap-around instead of -1 as int256

[zitup]

Component

Chisel

Have you ensured that all of these are up to date?

• Foundry
• Foundryup

What version of Foundry are you on?

0.2.0

What command(s) is the bug in?

1 - 2

Operating System

macOS (Intel)

Describe the bug

The result of 1 - 2 in Chisel is the max value of uint256, but it's -1 in forge test or remix.

Solc version is 0.8.26.

[mattsse]

but it's -1 in forge test or remix.

this can't be for uint256, if you do 1 - 2 then a signed type is inferred.

this might be a limitation due to how the chisel interpreter works, which will use abi.encode(1-2)

[zitup]

maybe we should find a way to avoid it, after all, it is inconsistent with the compiler's behavior

[zerosnacks]

For additional context: int256(1) - int256(2) (or int256(1) - 2)) in Chisel does correctly yield -1. This seems to be related to 1 and 2 being cast to uint256 by default and then correctly wrapping around.

I think this ticket can be resolved by documenting this quirk in the Foundry Book: https://book.getfoundry.sh/reference/chisel/

Beyond that I don't see a point of action here

[zitup]

For additional context: int256(1) - int256(2) (or int256(1) - 2)) in Chisel does correctly yield -1. This seems to be related to 1 and 2 being cast to uint256 by default and then correctly wrapping around.

I think this ticket can be resolved by documenting this quirk in the Foundry Book: https://book.getfoundry.sh/reference/chisel/

Beyond that I don't see a point of action here

What I think is chisel should be as consistent with evm as possible 🤔