lift the =dup hook (#21903)

* fixes tests again
* remove helper functions
* fixes closures, owned refs
* final cleanup

lib/system.nim

@@ -137,7 +137,7 @@ proc new*[T](a: var ref T, finalizer: proc (x: ref T) {.nimcall.}) {.
   ## **Note**: The `finalizer` refers to the type `T`, not to the object!
   ## This means that for each object of type `T` the finalizer will be called!
 
-proc `=wasMoved`[T](obj: var T) {.magic: "WasMoved", noSideEffect.} =
+proc `=wasMoved`*[T](obj: var T) {.magic: "WasMoved", noSideEffect.} =
   ## Generic `wasMoved`:idx: implementation that can be overridden.
 
 proc wasMoved*[T](obj: var T) {.inline, noSideEffect.} =
@@ -354,7 +354,7 @@ proc `=destroy`*[T](x: var T) {.inline, magic: "Destroy".} =
   discard
 
 when defined(nimHasDup):
-  proc `=dup`*[T](x: ref T): ref T {.inline, magic: "Dup".} =
+  proc `=dup`*[T](x: T): T {.inline, magic: "Dup".} =
     ## Generic `dup`:idx: implementation that can be overridden.
     discard
 

lib/system/arc.nim

@@ -200,10 +200,6 @@ proc nimDecRefIsLast(p: pointer): bool {.compilerRtl, inl.} =
       when traceCollector:
         cprintf("[DECREF] %p\n", cell)
 
-proc nimDupRef(dest: ptr pointer, src: pointer) {.compilerRtl, inl.} =
-  dest[] = src
-  if src != nil: nimIncRef src
-
 proc GC_unref*[T](x: ref T) =
   ## New runtime only supports this operation for 'ref T'.
   var y {.cursor.} = x