abi-coder support for fixed, ufixed and function types?

[theethernaut]

As far as I can tell, the abi-coder util supports all types listed in Solidity's documentation: https://solidity.readthedocs.io/en/v0.4.24/abi-spec.html#types

Except fixed, ufixed and function types, that is. Can you confirm this? And if so, are you planning to support these types?

[ricmoo]

That’s actually the oldest issue I opened 2 years ago, #3

:)

Is fixed still supported by Solidity? There was discussion at one point about removing it.

There are a lot of complications and potentially non-deterministic outputs when supporting fixed-point operations, depending on the optimizations used. Another issue (and this impacts non-fixed as well, so maybe moot) is the difference in computation for compile-time vs run-time evaluation...

If added, it may be a fairly opaque type, that would not intrinsically support mathematical operations, but could be cast to support them.

What type of support do you require/suggest?

[ricmoo]

(FYI: just confirmed fixed is still supported in 0.5)

[ricmoo]

Just found this little nugget to keep in mind. :)

"Fixed point numbers are not fully supported by Solidity yet. They can be declared, but cannot be assigned to or from."

https://solidity.readthedocs.io/en/v0.5.2/types.html?highlight=fixed#fixed-point-numbers

[theethernaut]

Thanks @ricmoo, I guess that 'non-full' support by Solidity is reason enough not to support it by the abi-coder. But what about function types?

What type of support do you require/suggest?

This question just arose while we were writing tests for ZeppelinOS's encodeCall utillity, which may use the abi-coder in the near future, and realized that the coder did not accept the mentioned types. The zos command line program accepts initializer function calls, and we want to make sure that our ABI encoding fully supports all the types that Solidity provides: https://github.com/zeppelinos/zos/blob/b6c93f11667c5bcc505506e4f21b0d35be54cfab/packages/lib/test/src/helpers/encodeCall.test.js

[ricmoo]

It does make sense to add... The object returned for now may be a bit bothersome to use, but I'll add support this week. :)

[ricmoo]

@ajsantander Have you actually been able to use the fixed/ufixed types? I've added support, but cannot test it because Solidity fails with UnimplementedFeatureError: Fixed point types not implemented.

[cgewecke]

Hi @ricmoo

Were you ever able to look at decoding Function types?

There is a corresponding issue at web3 2826 about decoding them when they are event params.

Have opened a tentative PR to fix there by re-mapping Function types to bytes24 per the Solidity spec:

If external function types are used outside of the context of Solidity, they are treated as the function type, which encodes the address followed by the function identifier together in a single bytes24 type

... but am wondering if you've already looked at this topic and there's more to it (or you're already fixing here).