BUG: TypeError in index coercion

Author: Matt Wittmann

doc/source/whatsnew/v0.18.1.txt

@@ -333,3 +333,5 @@ Bug Fixes
 
 
 - Bug in ``fill_value`` is ignored if the argument to a binary operator is a constant (:issue `12723`)
+
+- Bug in index coercion when falling back from ```RangeIndex``` construction (:issue:`12893`)

pandas/indexes/multi.py

@@ -666,7 +666,7 @@ def get_level_values(self, level):
         filled = algos.take_1d(unique.values, labels,
                                fill_value=unique._na_value)
         _simple_new = unique._simple_new
-        values = _simple_new(filled, self.names[num],
+        values = _simple_new(filled, name=self.names[num],
                              freq=getattr(unique, 'freq', None),
                              tz=getattr(unique, 'tz', None))
         return values

pandas/tests/indexes/test_multi.py

@@ -2130,3 +2130,12 @@ def test_partial_string_timestamp_multiindex(self):
         # Slicing date on first level should break (of course)
         with assertRaises(KeyError):
             df_swap.loc['2016-01-01']
+
+    def test_rangeindex_fallback_coercion_bug(self):
+        # GH 12893
+        foo = pd.DataFrame(np.arange(100).reshape((10, 10)))
+        bar = pd.DataFrame(np.arange(100).reshape((10, 10)))
+        df = pd.concat({'foo': foo.stack(), 'bar': bar.stack()}, axis=1)
+        df.index.names = ['fizz', 'buzz']
+        expected = [i for i in range(10) for j in range(10)]
+        self.assertTrue((df.index.get_level_values('fizz') == expected).all())