revert Index.__rsub__

Author: jbrockmendel

pandas/core/indexes/base.py

@@ -2267,10 +2267,6 @@ def __sub__(self, other):
         raise TypeError("cannot perform __sub__ with this index type: "
                         "{typ}".format(typ=type(self).__name__))
 
-    def __rsub__(self, other):
-        # TODO: name etc?  __radd__ doesn't pass it.
-        return Index(other - np.array(self))
-
     def __and__(self, other):
         return self.intersection(other)
 

pandas/tests/indexes/test_base.py

@@ -2308,6 +2308,9 @@ def test_ensure_index_from_sequences(self, data, names, expected):
                                     'pow', 'rpow', 'mod', 'divmod'])
 def test_generated_op_names(opname, indices):
     index = indices
+    if type(index) is pd.Index and opname == 'rsub':
+        # method doesn't exist, see GH#19723
+        return
     opname = '__{name}__'.format(name=opname)
     method = getattr(index, opname)
     assert method.__name__ == opname