From a7304d23a48d1b4777cd50efc725c070632f708e Mon Sep 17 00:00:00 2001
From: jbrockmendel <jbrockmendel@gmail.com>
Date: Thu, 16 Jan 2020 11:23:07 -0800
Subject: [PATCH] REF: stricter types for RangeIndex._simple_new

---
 pandas/core/indexes/base.py  |  6 +++++-
 pandas/core/indexes/range.py | 19 ++++++++-----------
 2 files changed, 13 insertions(+), 12 deletions(-)

diff --git a/pandas/core/indexes/base.py b/pandas/core/indexes/base.py
index 47daaa4958411..22a0097c6b95f 100644
--- a/pandas/core/indexes/base.py
+++ b/pandas/core/indexes/base.py
@@ -57,6 +57,7 @@
     ABCMultiIndex,
     ABCPandasArray,
     ABCPeriodIndex,
+    ABCRangeIndex,
     ABCSeries,
     ABCTimedeltaIndex,
 )
@@ -3105,7 +3106,10 @@ def reindex(self, target, method=None, level=None, limit=None, tolerance=None):
         if not isinstance(target, Index) and len(target) == 0:
             attrs = self._get_attributes_dict()
             attrs.pop("freq", None)  # don't preserve freq
-            values = self._data[:0]  # appropriately-dtyped empty array
+            if isinstance(self, ABCRangeIndex):
+                values = range(0)
+            else:
+                values = self._data[:0]  # appropriately-dtyped empty array
             target = self._simple_new(values, dtype=self.dtype, **attrs)
         else:
             target = ensure_index(target)
diff --git a/pandas/core/indexes/range.py b/pandas/core/indexes/range.py
index 5c79942efb908..1629396796b85 100644
--- a/pandas/core/indexes/range.py
+++ b/pandas/core/indexes/range.py
@@ -27,12 +27,14 @@
 import pandas.core.common as com
 from pandas.core.construction import extract_array
 import pandas.core.indexes.base as ibase
-from pandas.core.indexes.base import Index, _index_shared_docs, maybe_extract_name
+from pandas.core.indexes.base import _index_shared_docs, maybe_extract_name
 from pandas.core.indexes.numeric import Int64Index
 from pandas.core.ops.common import unpack_zerodim_and_defer
 
 from pandas.io.formats.printing import pprint_thing
 
+_empty_range = range(0)
+
 
 class RangeIndex(Int64Index):
     """
@@ -130,15 +132,10 @@ def from_range(cls, data, name=None, dtype=None):
         return cls._simple_new(data, dtype=dtype, name=name)
 
     @classmethod
-    def _simple_new(cls, values, name=None, dtype=None):
+    def _simple_new(cls, values: range, name=None, dtype=None) -> "RangeIndex":
         result = object.__new__(cls)
 
-        # handle passed None, non-integers
-        if values is None:
-            # empty
-            values = range(0, 0, 1)
-        elif not isinstance(values, range):
-            return Index(values, dtype=dtype, name=name)
+        assert isinstance(values, range)
 
         result._range = values
         result.name = name
@@ -482,7 +479,7 @@ def intersection(self, other, sort=False):
             return super().intersection(other, sort=sort)
 
         if not len(self) or not len(other):
-            return self._simple_new(None)
+            return self._simple_new(_empty_range)
 
         first = self._range[::-1] if self.step < 0 else self._range
         second = other._range[::-1] if other.step < 0 else other._range
@@ -492,7 +489,7 @@ def intersection(self, other, sort=False):
         int_low = max(first.start, second.start)
         int_high = min(first.stop, second.stop)
         if int_high <= int_low:
-            return self._simple_new(None)
+            return self._simple_new(_empty_range)
 
         # Method hint: linear Diophantine equation
         # solve intersection problem
@@ -502,7 +499,7 @@ def intersection(self, other, sort=False):
 
         # check whether element sets intersect
         if (first.start - second.start) % gcd:
-            return self._simple_new(None)
+            return self._simple_new(_empty_range)
 
         # calculate parameters for the RangeIndex describing the
         # intersection disregarding the lower bounds