fixes a closure iterator memory leaks, progress on #15076

compiler/injectdestructors.nim

@@ -787,7 +787,7 @@ proc p(n: PNode; c: var Con; s: var Scope; mode: ProcessMode): PNode =
               if ri.kind == nkEmpty and c.inLoop > 0:
                 ri = genDefaultCall(v.typ, c, v.info)
               if ri.kind != nkEmpty:
-                result.add moveOrCopy(v, ri, c, s, isDecl = true)
+                result.add moveOrCopy(v, ri, c, s, isDecl = false)
         else: # keep the var but transform 'ri':
           var v = copyNode(n)
           var itCopy = copyNode(it)

tests/arc/tclosureiter.nim

@@ -0,0 +1,36 @@
+discard """
+  cmd: '''nim c -d:nimAllocStats --gc:arc $file'''
+  output: '''(allocCount: 102, deallocCount: 102)'''
+"""
+
+type
+  FutureBase = ref object
+    someData: string
+
+const
+  # Just to occupy some RAM
+  BigData = "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa"
+
+iterator mainIter(): FutureBase {.closure.} =
+  for x in 0 .. 100:
+    var internalTmpFuture = FutureBase(someData: BigData)
+    yield internalTmpFuture
+
+proc main() =
+  var nameIterVar = mainIter
+  var next = nameIterVar()
+  while not isNil(next):
+    next = nameIterVar()
+    if not isNil(next):
+      doAssert next.someData.len == 97
+    # GC_unref(next)
+    # If you uncomment the GC_ref above,
+    # the program basically uses no memory after the run.
+    # but crashes with refc, which might indicate
+    # that arc/orc simply never frees the result of "next"?
+    if finished(nameIterVar):
+      break
+
+main()
+GC_fullCollect()
+echo getAllocStats()