Deepcopy model in LibtaskModel (#92)

* Move things around

* Add test, fix comments

* Copy

* Update Project.toml

---------

Co-authored-by: Hong Ge <[email protected]>

Author: FredericWantiez

Project.toml

@@ -1,7 +1,7 @@
 name = "AdvancedPS"
 uuid = "576499cb-2369-40b2-a588-c64705576edc"
 authors = ["TuringLang"]
-version = "0.5.3"
+version = "0.5.4"
 
 [deps]
 AbstractMCMC = "80f14c24-f653-4e6a-9b94-39d6b0f70001"

ext/AdvancedPSLibtaskExt.jl

@@ -32,8 +32,13 @@ function AdvancedPS.LibtaskModel(
     )
 end
 
+"""
+    copy(model::AdvancedPS.LibtaskModel)
+
+The task is copied (forked) and the inner model is deepcopied.
+"""
 function Base.copy(model::AdvancedPS.LibtaskModel)
-    return AdvancedPS.LibtaskModel(model.f, copy(model.ctask))
+    return AdvancedPS.LibtaskModel(deepcopy(model.f), copy(model.ctask))
 end
 
 const LibtaskTrace{R} = AdvancedPS.Trace{<:AdvancedPS.LibtaskModel,R}