interface view decoders

[S11001001]

Build upon #14313, and support #14969, by having InterfaceCompanion also supply a ValueDecoder<View>.

• ValueDecoder Interface #15017
• InterfaceCompanion's tparams should be <I, View>
• ContractTypeCompanion's tparams should be <Marker, Data>. ContractCompanion should pass Data for both. They should be I, View for InterfaceCompanion
• change the INTERFACE class we generate to pass the view type as the second tparam, and pass a ValueDecoder<View> as a param to super

[chunlokling-da]

I am thinking about whether to put the public final ValueDecoder<Data> valueDecoder in InterfaceCompanion or ContractTypeCompanion. I believe we ultimately would like to put it in ContractTypeCompanion as the both template and interface should provide a ValueDecoder<>. I tried to put it in ContractTypeCompanion but I found some changes required in generate Template class. @S11001001 Do you think it is good enough for this issue to put the valueDecoder in InterfaceCompanion but not in ContractTypeCompanion yet?

[S11001001]

Do you think it is good enough for this issue to put the valueDecoder in InterfaceCompanion but not in ContractTypeCompanion yet?

@chunlokling-da It can be put in all three. Define this (package-private) method:

<Z> Z fold(Function<? super ContractCompanion<?, ?, Data>, Z> template,
    Function<? super InterfaceCompanion<Marker, Data>, Z> iface)

and then implementing valueDecoder in the ContractTypeCompanion by calling the other two should become straightforward.

[S11001001]

@chunlokling-da On the other hand, maybe not so straightforward. Yeah, it's fine to have it in the InterfaceCompanion but not in ContractTypeCompanion for this issue. However, I think this might imply that we have a problem with decoding interface contract IDs that we should fix separately.