Should custom errors be given a bespoke type?

Language Design
1

I find it a bit confusing that when defining a custom error like this:

interface MyInterface {
    error MyCustomError();
}

The type of MyInterface.MyCustomError is function() pure.

I know that custom errors are ABI encoded identically as functions, but I think that they deserve a bespoke type.

My vote would go to error, which under the hood would be an alias for bytes24 (just like function).

False positive spam, my posts have been hidden by the system
2

Where is it reported as function() pure? I wanted to check if we do this by design or if it’s an error but I can’t find this.

I just checked the solc --abi output and I see this:

[{"inputs":[],"name":"MyCustomError","type":"error"}]

In solc --ast-compact-json the error looks like this:

     [
        {
          "errorSelector": "4e7254d6",
          "id": 2,
          "name": "MyCustomError",
          "nameLocation": "34:13:0",
          "nodeType": "ErrorDefinition",
          "parameters":
          {
            "id": 1,
            "nodeType": "ParameterList",
            "parameters": [],
            "src": "47:2:0"
          },
          "src": "28:22:0"
        }
      ]

And in solc --hashes:

Error signatures:
4e7254d6: MyCustomError()
3

Where is it reported as function() pure ?

I first saw it in a hint in VSCode but this doesn’t look like a problem with the vscode-solidity extension:

Screen Shot 2022-04-04 at 4.57.06 PM
Screen Shot 2022-04-04 at 4.57.06 PM1090Ă—106 13 KB

When I run the tests with forge, the compiler run fails with the following error:

Error:
   0: Compiler run failed
      TypeError: Explicit type conversion not allowed from "function () pure" to "bytes4".
        --> /path/to/my/test/file.t.sol:33:25:
         |
      33 |         vm.expectRevert(bytes4(MyInterface.MyCustomError));
         |                         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^


   0:

Location:
   cli/src/cmd/utils.rs:43

Environment:

  • solidity v0.8.13+commit.abaa5c0e
  • forge v0.2.0 (a0db055 2022-04-03T00:03:53.441110+00:00)
4

Oh, so it’s in an error message. True, we should improve that. I suspect that something similar happens when you try it with an event. Can you submit an issue?

1 Like
5

Can you submit an issue?

I did it! See issue #12896. I would have linked to it but for some reason the forum keeps considering my GitHub links as spam and hiding my posts.

6

Thanks! I approved your posts and gave you a higher “trust level” so hopefully the false flag issue is resolved now.

1 Like