Rule-based overriding of default actions

[ianbollinger]

It's necessary for the author to be able to write something like:

object "foo" "bar"
|> insteadOf taking (\args -> {- replacement action -})

Other comibinators would have names such as "before" and "after".

I'm a bit weary about doing this, however, because the action name would need to be indexed by string to be fully extensible (documenting this could be ameliorated by making a constant for each one.) Additionally, the user would also have to know the format of [args] being passed into the given action, which would require even more documentation for the author to get correct.