Reference types are handled by `without` statement with error

questionable/private/binderror.nim

@@ -21,9 +21,18 @@ macro captureBindError*(error: var ref CatchableError, expression): auto =
     # return the evaluated result
     evaluated
 
-func error[T](option: Option[T]): ref CatchableError =
+func error[T](_: Option[T]): ref CatchableError =
   newException(ValueError, "Option is set to `none`")
 
+func error[T](_: ref T): ref CatchableError =
+  newException(ValueError, "ref is nil")
+
+func error[T](_: ptr T): ref CatchableError =
+  newException(ValueError, "ptr is nil")
+
+func error[Proc: proc | iterator](_: Proc): ref CatchableError =
+  newException(ValueError, "proc or iterator is nil")
+
 macro bindFailed*(expression: typed) =
   ## Called when a binding (=?) fails.
   ## Assigns an error to the error variable (specified in captureBindError())

testmodules/results/test.nim

@@ -326,6 +326,48 @@ suite "result":
     test1()
     test2()
 
+  test "without statement with error handles references as well":
+    proc test =
+      var x: ref int = nil
+      without a =? x, error:
+        check error.msg == "ref is nil"
+        return
+      fail
+
+    test()
+
+  test "without statement with error handles pointers as well":
+    proc test =
+      var x: ptr int = nil
+      without a =? x, error:
+        check error.msg == "ptr is nil"
+        return
+      fail
+
+    test()
+
+  test "without statement with error handles closures as well":
+    proc test =
+      var x = proc = discard
+      x = nil
+      without a =? x, error:
+        check error.msg == "proc or iterator is nil"
+        return
+      fail
+
+    test()
+
+  test "without statement with error handles iterators as well":
+    when (NimMajor, NimMinor) != (2, 0):
+      proc test =
+        var x: iterator: int = nil
+        without a =? x, error:
+          check error.msg == "proc or iterator is nil"
+          return
+        fail
+
+      test()
+
   test "without statement with error can be used more than once":
     proc test =
       without a =? 42.success, error: