Modify hash for HashSet to use xor to mix hash of items.

lib/pure/collections/sets.nim

@@ -18,7 +18,7 @@
 ## that ``=`` performs a copy of the set.
 
 import
-  hashes, math, algorithm
+  hashes, math
 
 {.pragma: myShallow.}
 when not defined(nimhygiene):
@@ -123,11 +123,8 @@ iterator items*[A](s: HashSet[A]): A =
 proc hash*[A](s: HashSet[A]): Hash =
   ## hashing of HashSet
   assert s.isValid, "The set needs to be initialized."
-  var hcs: seq[Hash]
   for h in 0..high(s.data):
-    hcs.add(s.data[h].hcode)
+    result = result xor s.data[h].hcode
-  for hc in sorted(hcs, cmp[int]):
-    result = result !& hc
   result = !$result
 
 const

tests/collections/tsets.nim

@@ -85,10 +85,6 @@ block hashForHashedSet:
   var hashSeq: seq[Hash] = @[]
   doAssert s1 == s2
   doAssert hash(s1) == hash(s2)
-  for c in seq1:
-    if (not (hash(c) in hashSeq)):
-      hashSeq.add(hash(c))
-  doAssert hash(s1) == hash(sorted(hashSeq, cmp[Hash]))
 
 block hashForOrderdSet:
   let