Component

Forge

Describe the feature you would like

Motivation

One of the hardest things to properly test in Foundry is EIP-712 encoding and hashing. Efficiently encoding EIP-712 in Solidity generally requires manual declaration of string types and abi encoding of values. In testing, there is no way to double-check that this encoding is actually consistent with the EIP-712 spec. Some catches and edge cases of EIP-712 spec are especially easy to accidentally mess up, i.e. alphabetic ordering of sub-types. This is especially important as signed messages become more widely used, i.e. for EIP-4337.

Currently the best approach for this afaik is to write typescript tests using ethers' TypedDataEncoder to verify

Feature

A cheatcode that creates canonical encodings / typehashes for EIP-712 objects.
Ideal API:

vm.hashType(MyStruct) => bytes32 typeHash
vm.hashStruct(MyStruct struct) => bytes32 hash

I'm not sure how easy the introspection will be, but this would be an invaluable feature to cover one of the last un-testable cases in Foundry

Additional context

No response