AbiCoder: `function` elementary Solidity type not supported

[sealer3]

Ethers Version

6.7.1

Search Terms

elementary, invalid param type

Describe the Problem

function is an elementary Solidity type which is ABI-encoded the same as bytes24. It consists of an address (20 bytes) followed by a function selector (4 bytes). Documentation ref: https://docs.soliditylang.org/en/latest/abi-spec.html#types

It seems like ethers' ABI coder has never had support for this type, so errors are thrown when trying to decode an ABI containing a function type. What's funny is the function type was added to Solidity almost 7 years ago, but I guess it hasn't been popular enough for anyone to notice: ethereum/solidity#1122

Example contract (see getFunction function):
(Otterscan) https://sepolia.otterscan.io/address/0xb0e9daBA710617b2C398b3987716B2F1f36bB228/contract (select Sourcify Servers data source from hamburger in upper right)
(Etherscan) https://sepolia.etherscan.io/address/0xb0e9daBA710617b2C398b3987716B2F1f36bB228#code

Code Snippet

ethers.ParamType.from("function")

Contract ABI

[{"inputs":[{"internalType":"function () external","name":"val","type":"function"}],"name":"getFunction","outputs":[{"internalType":"function () external","name":"","type":"function"}],"stateMutability":"pure","type":"function"}]

Errors

TypeError: invalid param type (argument="obj", value="function", code=INVALID_ARGUMENT, version=6.7.1)
    at makeError (node_modules/ethers/lib.commonjs/utils/errors.js:118:21)
    at assert (node_modules/ethers/lib.commonjs/utils/errors.js:142:15)
    at assertArgument (node_modules/ethers/lib.commonjs/utils/errors.js:154:5)
    at ParamType.from (node_modules/ethers/lib.commonjs/abi/fragments.js:625:47) {
  code: 'INVALID_ARGUMENT',
  argument: 'obj',
  value: 'function'
}

Environment

node.js (v12 or newer)

Environment (Other)

No response

[ricmoo]

Yes, it's been on my backlog for some time (there are a few older references, here is one).

You are correct, it hasn't been popular enough to really get bumped up in priority, but it of course makes sense to add.

I can investigate this for the next minor bump. :)