feat(ethers-core/abi): impl AbiArrayType for u8

[meetmangukiya]

Motivation

Had a compilation error earlier in abigen:

1198 |         pub pairs_to_swap: ::std::vec::Vec<(u8, u8)>,
     |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ the trait `AbiArrayType` is not implemented for `u8`

So implementing it.

Solution

PR Checklist

• Added Tests
• Added Documentation
• Updated the changelog

[meetmangukiya]

I am not entirely sure if this is breaking anything or any compat. I defer to experts.

[gakonst]

Yeah this is not the right solution here, because now it won't encode fixed length arrays..need to think about this a bit more.

[mattsse]

AbiArrayType is such an ugly hack ...

but the right way to fix this is to implement this manually for tuples of u8

impl AbiArrayType for Vec<(u8, u8)>

impl AbiArrayType for Vec<(u8, u8, u8)>

etc...

[meetmangukiya]

@mattsse wouldn't it still fail when there's some tuple like Vec<(u8, T, ...)>?

[mattsse]

yes this is a limitation and super ugly.

we could generate all those variants, I believe there is already a macro for tuples

[meetmangukiya]

Shouldn't

ethers-rs/ethers-core/src/abi/mod.rs

Lines 159 to 162 in 6ff5675

	impl<$($ty, )+> AbiArrayType for ($($ty,)+) where
	$(
	$ty: AbiType,
	)+ {}

implement AbiArrayType for different variant of tuples and on top of that

ethers-rs/ethers-core/src/abi/mod.rs

Line 93 in 6ff5675

impl<T: AbiArrayType> AbiArrayType for Vec<T> {}

implement AbiArrayType for Vec<T>?

which should mean we shouldn't need any of these?

impl AbiArrayType for Vec<(u8, u8)> {}

impl AbiArrayType for Vec<(u8, u8, u8)> {}

[meetmangukiya]

Pasting complete error for more context:

error[E0277]: the trait bound `u8: AbiArrayType` is not satisfied
    --> mean-finance/src/contracts/dcahub_companion.rs:1198:9
     |
1198 |         pub pairs_to_swap: ::std::vec::Vec<(u8, u8)>,
     |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ the trait `AbiArrayType` is not implemented for `u8`
     |
     = help: the following implementations were found:
               <i128 as AbiArrayType>
               <i16 as AbiArrayType>
               <i32 as AbiArrayType>
               <i64 as AbiArrayType>
             and 5 others
     = note: required because of the requirements on the impl of `AbiArrayType` for `(u8, u8)`
     = note: required because of the requirements on the impl of `AbiType` for `Vec<(u8, u8)>`

I couldn't find this exact trait bound(u8: AbiArrayType) causing this error.

ethers-rs/ethers-core/src/abi/mod.rs

Lines 88 to 92 in a43a9b8

	impl<T: AbiArrayType> AbiType for Vec<T> {
	fn param_type() -> ParamType {
	ParamType::Array(Box::new(T::param_type()))
	}
	}

would require for T i.e. (u8, u8) to be trait bounded by AbiArrayType.

which it should be because of this implementation

ethers-rs/ethers-core/src/abi/mod.rs

Lines 165 to 168 in a43a9b8

	impl<$($ty, )+> AbiArrayType for ($($ty,)+) where
	$(
	$ty: AbiType,
	)+ {}

now, this implementation in turn bounds the tuple element type T to be trait bound by AbiType. However, the error seems to be that T needs to be bound by AbiArrayType. Where is that trait bound coming from?

[mattsse]

this trait is required because of the special Vec<u8> => Bytes condition so it's sole purpose is to not be implemented by u8

need some manual impls for u8 tuples unfortunately

[mattsse]

this defeats the whole purpose of this trait.

[meetmangukiya]

The currently pushed code is certainly wrong. Can you check the comment #1140 (comment) regarding the manual impls for u8 tuples? Also, I don't think we need to implement AbiArrayType for tuples for fixing this error, tuples already have AbiArrayType implemented IIUC

ethers-rs/ethers-core/src/abi/mod.rs

Lines 165 to 168 in a43a9b8

	impl<$($ty, )+> AbiArrayType for ($($ty,)+) where
	$(
	$ty: AbiType,
	)+ {}

For the broader issue and source of error #1140 (comment)

[mattsse]

Shouldn't

ethers-rs/ethers-core/src/abi/mod.rs

Lines 159 to 162 in 6ff5675

	impl<$($ty, )+> AbiArrayType for ($($ty,)+) where
	$(
	$ty: AbiType,
	)+ {}

implement AbiArrayType for different variant of tuples and on top of that

ethers-rs/ethers-core/src/abi/mod.rs

Line 93 in 6ff5675

impl<T: AbiArrayType> AbiArrayType for Vec<T> {}

implement AbiArrayType for Vec<T>?
which should mean we shouldn't need any of these?

impl AbiArrayType for Vec<(u8, u8)> {}

impl AbiArrayType for Vec<(u8, u8, u8)> {}

interesting, need to check this manually what's going on here

[mattsse]

@meetmangukiya you're of course right: #1143

can you share the whole struct and its derive macros that's causing the issue, perhaps we're generating wrong trait bounds somewhere

[meetmangukiya]

    #[derive(
        Clone,
        Debug,
        Default,
        Eq,
        PartialEq,
        ethers :: contract :: EthCall,
        ethers :: contract :: EthDisplay,
    )]
    #[ethcall(
        name = "getNextSwapInfo",
        abi = "getNextSwapInfo(address[],(uint8,uint8)[])"
    )]
    pub struct GetNextSwapInfoCall {
        pub tokens: ::std::vec::Vec<ethers::core::types::Address>,
        pub pairs: ::std::vec::Vec<(u8, u8)>,
    }

    #[derive(
        Clone,
        Debug,
        Default,
        Eq,
        PartialEq,
        ethers :: contract :: EthCall,
        ethers :: contract :: EthDisplay,
    )]
    #[ethcall(
        name = "swap",
        abi = "swap(address[],(uint8,uint8)[],address,address,uint256[],bytes)"
    )]
    pub struct SwapCall {
        pub tokens: ::std::vec::Vec<ethers::core::types::Address>,
        pub pairs_to_swap: ::std::vec::Vec<(u8, u8)>,
        pub reward_recipient: ethers::core::types::Address,
        pub callback_handler: ethers::core::types::Address,
        pub borrow: ::std::vec::Vec<ethers::core::types::U256>,
        pub data: ethers::core::types::Bytes,
    }

[meetmangukiya]

Just rebased my abigen binary over latest ethers-rs and the generated code compiles fine 💀. I apologise for the wasted time @mattsse.

New code looks like

    #[derive(
        Clone,
        Debug,
        Default,
        Eq,
        PartialEq,
        ethers :: contract :: EthCall,
        ethers :: contract :: EthDisplay,
    )]
    #[ethcall(
        name = "getNextSwapInfo",
        abi = "getNextSwapInfo(address[],(uint8,uint8)[])"
    )]
    pub struct GetNextSwapInfoCall {
        pub tokens: ::std::vec::Vec<ethers::core::types::Address>,
        pub pairs: ::std::vec::Vec<PairIndexes>,
    }

[mattsse]

great!
just added this to confirm: #1144