Update args at copy

[FredericWantiez]

In AdvancedPS we often need to mutate the input of the the TapedFunction to handle random streams. It would be great if we could do something like:

function (model::Model) (rng::Random.AbstractRNG)
   ...
end

rng1 = Random.MersenneTwister()
task = Litbtask.TapedTask(model, rng1)

Libtask.consume(task)

new_rng = Random.MersenneTwister()
task2 = Libtask.copy(task, new_rng)

Libtask.consume(task) # Generates random numbers from rng1
Libtask.consume(task2) # Generates random numbers from new_rng

but for this to work we need to update the args... and bindings appropriately when we copy the running task.

This is just a draft, I'm not sure about all the implications of this change, especially with #138

[KDr2]

I think storing the args in TapedTask will be more intuitive and it can keep the API unchanged.

diff --git a/src/tapedtask.jl b/src/tapedtask.jl
index 71656a3..8b10506 100644
--- a/src/tapedtask.jl
+++ b/src/tapedtask.jl
@@ -6,6 +6,7 @@ end
 struct TapedTask{F}
     task::Task
     tf::TapedFunction{F}
+    args
     produce_ch::Channel{Any}
     consume_ch::Channel{Int}
     produced_val::Vector{Any}
@@ -13,10 +14,11 @@ struct TapedTask{F}
     function TapedTask(
         t::Task,
         tf::TapedFunction{F},
+        args,
         produce_ch::Channel{Any},
         consume_ch::Channel{Int}
     ) where {F}
-        new{F}(t, tf, produce_ch, consume_ch, Any[])
+        new{F}(t, tf, args, produce_ch, consume_ch, Any[])
     end
 end

@@ -161,7 +163,7 @@ Base.IteratorEltype(::Type{<:TapedTask}) = Base.EltypeUnknown()

 function Base.copy(t::TapedTask)
     tf = copy(t.tf)
-    new_t = TapedTask(tf)
+    args = do_tape_copy_on(t.args...) # !!!
+    new_t = TapedTask(tf, args...) 
     storage = t.task.storage::IdDict{Any,Any}
     new_t.task.storage = copy(storage)
     new_t.task.storage[:tapedtask] = new_t

[yebai]

Many thanks, @KDr2 and @FredericWantiez- it looks good and I'm happy to merge once CI passes.