fix error binding in without statement on multiple threads

questionable/private/binderror.nim

@@ -1,7 +1,7 @@
 import std/options
 
 var captures {.global, compileTime.}: int
-var errorVariable: ptr ref CatchableError
+var errorVariable {.threadvar.}: ptr ref CatchableError
 
 template captureBindError*(error: var ref CatchableError, expression): auto =
   let previousErrorVariable = errorVariable

testmodules/results/test.nim

@@ -3,8 +3,11 @@ import std/options
 import std/sequtils
 import std/strutils
 import std/sugar
+import std/threadpool
 import pkg/questionable/results
 
+{.experimental: "parallel".}
+
 suite "result":
 
   let error = newException(CatchableError, "error")
@@ -401,6 +404,14 @@ suite "result":
 
     foo()
 
+  test "without statement with error works with multiple threads":
+    proc fail(number: int) =
+      without _ =? int.failure "error" & $number, error:
+        check error.msg == "error" & $number
+    parallel:
+      for i in 0..<1000:
+        spawn fail(i)
+
   test "catch can be used to convert exceptions to results":
     check parseInt("42").catch == 42.success
     check parseInt("foo").catch.error of ValueError