fixes #24658; cpp compilation failure on Nim 2.2.x (#24663)

fixes #24658

tests/cpp/tconstructor.nim

@@ -128,4 +128,10 @@ block:
     var b = makeBoo()
     var b2 = makeBoo2()
 
-  main()
+  main()
+
+block: # bug #24658
+  type
+    A {.importcpp: "A".} = object
+
+  proc a(something: ptr cint = nil): A {.cdecl, constructor, importcpp: "A(@)".}