fix hash of PermutationGroup_generic

src/sage/groups/perm_gps/permgroup.py

@@ -762,6 +762,22 @@ def _magma_init_(self, magma):
         g = ', '.join([g._gap_cycle_string() for g in self.gens()])
         return 'PermutationGroup<%s | %s>' % (self.degree(), g)
 
+    def __hash__(self):
+        r"""
+        Return a hash value for ``self``.
+
+        TESTS::
+
+            sage: G = PermutationGroup([(1,2,3), (1,3)])
+            sage: G == SymmetricGroup(3)
+            True
+            sage: G.gens() == SymmetricGroup(3).gens()
+            False
+            sage: G in set([SymmetricGroup(3)])
+            True
+        """
+        return hash(self.cardinality())
+
     def __richcmp__(self, right, op):
         """
         Compare ``self`` and ``right``.

src/sage/groups/perm_gps/permgroup_named.py

@@ -109,21 +109,15 @@
 
 class PermutationGroup_unique(CachedRepresentation, PermutationGroup_generic):
     """
-    .. TODO::
-
-        Fix the broken hash. ::
-
-            sage: G = SymmetricGroup(6)
-            sage: G3 = G.subgroup([G((1,2,3,4,5,6)),G((1,2))])
-            sage: hash(G) == hash(G3)  # todo: Should be True!
-            False
-
     TESTS::
 
         sage: G = SymmetricGroup(6)
         sage: G3 = G.subgroup([G((1,2,3,4,5,6)),G((1,2))])
         sage: G == G3
         True
+
+        sage: hash(G) == hash(G3)
+        True
     """
     @weak_cached_function
     def __classcall__(cls, *args, **kwds):
@@ -3513,7 +3507,7 @@
         [ 2  0 -1 -2  0  1]
         [ 2  0 -1  2  0 -1]
         sage: def numgps(n): return ZZ(libgap.NumberSmallGroups(n))
         sage: all(SmallPermutationGroup(n,k).id() == [n,k]
         ....:     for n in [1..64] for k in [1..numgps(n)])
         True
         sage: H = SmallPermutationGroup(6,1)