Fix error when using an existing name as error variable

questionable/withoutresult.nim

@@ -1,12 +1,16 @@
+import std/macros
 import ./without
 import ./private/binderror
 
-template without*(condition, errorname, body): untyped =
+macro without*(condition, errorname, body): untyped =
   ## Used to place guards that ensure that a Result contains a value.
   ## Exposes error when Result does not contain a value.
 
-  var error: ref CatchableError
+  let errorIdent = ident $errorname
 
-  without captureBindError(error, condition):
-    template errorname: ref CatchableError = error
-    body
+  quote do:
+    var error: ref CatchableError
+
+    without captureBindError(error, `condition`):
+      template `errorIdent`: ref CatchableError = error
+      `body`

testmodules/result/test.nim

@@ -281,6 +281,15 @@ suite "result":
         check e2.msg == "error2"
       check e1.msg == "error1"
 
+  test "without statement works in generic code using existing error name":
+    let existingName {.used.} = "some variable"
+
+    proc shouldCompile(_: type int): ?!int =
+      without _ =? int.failure "error", existingName:
+        return success 42
+
+    discard int.shouldCompile()
+
   test "without statements with error work in nested calls":
     proc bar(): ?!int =
       without _ =? int.failure "error", err: