Add support for tuples in the ABI

[francescortiz]

I found out that when the generator fins a tuple it outputs tuple-ERROR!. The tuple implementation could consist of two phases:

1. Just defining the tuple:

testFunc : Address -> ( String, BigInt ) -> Call BigInt

2. Later on adding a solidity parser that looks for struct definitions and creates a type alias for those cases:

type alias SomeTypeWithAssociatedStruct = 
  { name : String
  , id : BigInt
  }

testFunc : Address -> SomeTypeWithAssociatedStruct -> Call BigInt

I have almost no experience with Haskell, but I will try implement if it is not implemented when the time comes when I need to use it.

[cmditch]

Can you post a small solidity contract which produces the error? Need to get an idea of what solidity code is producing the erroneous ABI.

Thanks

[cmditch]

@francescortiz Come to think of it, I'm not aware of a tuple type in the ABI. Public and externally callable functions with multiple parameters are indeed supported by elm-ethereum/elm-ethereum-generator. Very curious to see how your generating an ABI which includes a tuple type. Just to clarify, you're using Solidity?

Edit: Nvm, I see now. Looks like as of 0.4.19 you can pass structs in. I'd say for the time being see if you can pass multiple parameters into the function, instead of a single struct parameter. Or bake up an implementation of tuple encoding in elm-ethereum, and we can add support in elm-ethereum-generator.

Thanks for bringing this to my attention! Such a fast moving world.