Fix #268 2, do not rely on well implemented __ne__ for keys in pmaps,…

… instead do explicit inversion of equality comparison when checking for inequality

pyrsistent/_pmap.py

@@ -413,7 +413,8 @@ def set(self, key, val):
                 for k, v in bucket:
                     if k == key:
                         if v is not val:
-                            new_bucket = [(k2, v2) if k2 != k else (k2, val) for k2, v2 in bucket]
+                            # Use `not (k2 == k)` rather than `!=` to avoid relying on a well implemented `__ne__`, see #268.
+                            new_bucket = [(k2, v2) if not (k2 == k) else (k2, val) for k2, v2 in bucket]
                             self._buckets_evolver[index] = new_bucket
 
                         return self
@@ -476,7 +477,8 @@ def remove(self, key):
             index, bucket = PMap._get_bucket(self._buckets_evolver, key)
 
             if bucket:
-                new_bucket = [(k, v) for (k, v) in bucket if k != key]
+                # Use `not (k == key)` rather than `!=` to avoid relying on a well implemented `__ne__`, see #268.
+                new_bucket = [(k, v) for (k, v) in bucket if not (k == key)]
                 size_diff = len(bucket) - len(new_bucket)
                 if size_diff > 0:
                     self._buckets_evolver[index] = new_bucket if new_bucket else None

tests/map_test.py

@@ -547,5 +547,5 @@ def test_pmap_removal_with_broken_classes_deriving_from_namedtuple():
 
     # Both items are removed due to how they are compared for inequality
     assert BrokenPerson('X') not in s
-    assert BrokenItem('X') not in s
-    assert len(s) == 0
+    assert BrokenItem('X') in s
+    assert len(s) == 1