support UncheckedArray[T] in repr_v2.nim (#20816)

lib/system/repr_v2.nim

@@ -189,4 +189,7 @@ proc repr*[T](x: openArray[T]): string =
   ##
   ## .. code-block:: Nim
   ##   $(@[23, 45].toOpenArray(0, 1)) == "[23, 45]"
-  collectionToRepr(x, "[", ", ", "]")
+  collectionToRepr(x, "[", ", ", "]")
+
+proc repr*[T](x: UncheckedArray[T]): string =
+  "[...]"

tests/arc/trepr.nim

@@ -9,6 +9,7 @@ nil
 2
 Obj(member: ref @["hello"])
 ref (member: ref @["hello"])
+ObjUa(v: 0, a: [...])
 '''
 """
 
@@ -87,3 +88,10 @@ macro extract(): untyped =
   test(parseExpr("discard"))
   
 extract()
+
+type
+  ObjUa = ref object
+    v: int
+    a: UncheckedArray[char]
+
+echo ObjUa().repr