A trait encompassing both Iterable<T>`Iterablefor some fixed` for some fixed T`Tand` and
FromIterator<U>`FromIteratorfor _all_` for all U`U(where HKT comes in). The train could provide e.g. a default` (where HKT comes in). The train
could provide e.g. a default map`map` method producing the same kind of
the container, but with a new type parameter.
Monadic-generic programming? Can we add this without deprecating
huge swaths of the API (including Option::map`Option::map,`, option::collect`option::collect,`,
result::collect`result::collect,`, try!`try!` etc.