1 files changed, 26 insertions, 8 deletions
diff --git a/lib/sqlalchemy/util/_collections.py b/lib/sqlalchemy/util/_collections.py
index 86a90828a..c0a24ba4f 100644
--- a/lib/sqlalchemy/util/_collections.py
+++ b/lib/sqlalchemy/util/_collections.py
@@ -1,16 +1,17 @@
 # util/_collections.py
-# Copyright (C) 2005-2013 the SQLAlchemy authors and contributors <see AUTHORS file>
+# Copyright (C) 2005-2014 the SQLAlchemy authors and contributors <see AUTHORS file>
 #
 # This module is part of SQLAlchemy and is released under
 # the MIT License: http://www.opensource.org/licenses/mit-license.php
 
 """Collection classes and helpers."""
 
-import itertools
+from __future__ import absolute_import
 import weakref
 import operator
 from .compat import threading, itertools_filterfalse
 from . import py2k
+import types
 
 EMPTY_SET = frozenset()
 
@@ -650,19 +651,31 @@ class IdentitySet(object):
 
 
 class WeakSequence(object):
-    def __init__(self, elements):
-        self._storage = weakref.WeakValueDictionary(
-            (idx, element) for idx, element in enumerate(elements)
-        )
+    def __init__(self, __elements=()):
+        self._storage = [
+            weakref.ref(element, self._remove) for element in __elements
+        ]
+
+    def append(self, item):
+        self._storage.append(weakref.ref(item, self._remove))
+
+    def _remove(self, ref):
+        self._storage.remove(ref)
+
+    def __len__(self):
+        return len(self._storage)
 
     def __iter__(self):
-        return iter(self._storage.values())
+        return (obj for obj in
+                    (ref() for ref in self._storage) if obj is not None)
 
     def __getitem__(self, index):
         try:
-            return self._storage[index]
+            obj = self._storage[index]
         except KeyError:
             raise IndexError("Index %s out of range" % index)
+        else:
+            return obj()
 
 
 class OrderedIdentitySet(IdentitySet):
@@ -743,6 +756,11 @@ class UniqueAppender(object):
     def __iter__(self):
         return iter(self.data)
 
+def coerce_generator_arg(arg):
+    if len(arg) == 1 and isinstance(arg[0], types.GeneratorType):
+        return list(arg[0])
+    else:
+        return arg
 
 def to_list(x, default=None):
     if x is None: