Fix TypeError: unhashable type: 'Symbol' (and 'String')

sexpdata.py

@@ -451,6 +451,14 @@ def __eq__(self, other):
     def __ne__(self, other):
         return not self == other
 
+    def __hash__(self):
+        """
+        >>> D = {'a': 1, String('a'): 2, Symbol('a'): 3}
+        >>> len(D)
+        3
+        """
+        return unicode.__hash__(self)
+
     _lisp_quoted_specials = [  # from Pymacs
         ('\\', '\\\\'),    # must come first to avoid doubly quoting "\"
         ('"', '\\"'), ('\b', '\\b'), ('\f', '\\f'),

test_sexpdata.py

@@ -88,6 +88,17 @@ def test_parse_special_symbols(self):
                   r'\ ', r'\.', r'\,', r'\?', r'\;', r'\#']:
             self.assert_parse(s, Symbol(Symbol.unquote(s)))
 
+    def test_hashable_and_distinct(self):
+        d = {
+            String("A"): "StrA",
+            Symbol("A"): "SymA",
+            "A": "strA",
+        }
+        self.assertEqual(3, len(d))
+        self.assertEqual("StrA", d[String("A")])
+        self.assertEqual("SymA", d[Symbol("A")])
+        self.assertEqual("strA", d["A"])
+
 
 class TestParseFluctuation(BaseTestCase):