ARC: ported the GC tests over to --gc:arc

tests/gc/closureleak.nim

@@ -3,20 +3,28 @@ discard """
   disabled: "32bit"
 """
 
-from strutils import join
-
 type
-  TFoo * = object
+  TFoo* = object
     id: int
     fn: proc(){.closure.}
 var foo_counter = 0
 var alive_foos = newseq[int](0)
 
-proc free*(some: ref TFoo) =
-  #echo "Tfoo #", some.id, " freed"
-  alive_foos.del alive_foos.find(some.id)
+when defined(gcDestructors):
+  proc `=destroy`(some: var TFoo) =
+    alive_foos.del alive_foos.find(some.id)
+    `=destroy`(some.fn)
+
+else:
+  proc free*(some: ref TFoo) =
+    #echo "Tfoo #", some.id, " freed"
+    alive_foos.del alive_foos.find(some.id)
+
 proc newFoo*(): ref TFoo =
-  new result, free
+  when defined(gcDestructors):
+    new result
+  else:
+    new result, free
 
   result.id = foo_counter
   alive_foos.add result.id