From 31947401e054ab6c389eee031e1166ecd5b7e84c Mon Sep 17 00:00:00 2001
From: Brock <jbrockmendel@gmail.com>
Date: Fri, 19 Feb 2021 18:40:24 -0800
Subject: [PATCH] REF: De-duplicate ExtensionIndex._validate_fill_value

---
 pandas/core/indexes/datetimelike.py |  6 ------
 pandas/core/indexes/extension.py    | 14 ++++++++++----
 pandas/core/indexes/interval.py     |  3 ---
 3 files changed, 10 insertions(+), 13 deletions(-)

diff --git a/pandas/core/indexes/datetimelike.py b/pandas/core/indexes/datetimelike.py
index b2c67ae2f0a00..afbddefae5e72 100644
--- a/pandas/core/indexes/datetimelike.py
+++ b/pandas/core/indexes/datetimelike.py
@@ -627,12 +627,6 @@ def insert(self, loc: int, item):
         result._data._freq = self._get_insert_freq(loc, item)
         return result
 
-    def _validate_fill_value(self, value):
-        """
-        Convert value to be insertable to ndarray.
-        """
-        return self._data._validate_setitem_value(value)
-
     # --------------------------------------------------------------------
     # Join/Set Methods
 
diff --git a/pandas/core/indexes/extension.py b/pandas/core/indexes/extension.py
index 0097959245686..f1418869713d6 100644
--- a/pandas/core/indexes/extension.py
+++ b/pandas/core/indexes/extension.py
@@ -4,6 +4,7 @@
 from typing import (
     List,
     TypeVar,
+    Union,
 )
 
 import numpy as np
@@ -25,7 +26,7 @@
     ABCSeries,
 )
 
-from pandas.core.arrays import ExtensionArray
+from pandas.core.arrays import IntervalArray
 from pandas.core.arrays._mixins import NDArrayBackedExtensionArray
 from pandas.core.indexers import deprecate_ndim_indexing
 from pandas.core.indexes.base import Index
@@ -216,7 +217,7 @@ class ExtensionIndex(Index):
     # The base class already passes through to _data:
     #  size, __len__, dtype
 
-    _data: ExtensionArray
+    _data: Union[IntervalArray, NDArrayBackedExtensionArray]
 
     __eq__ = _make_wrapped_comparison_op("__eq__")
     __ne__ = _make_wrapped_comparison_op("__ne__")
@@ -240,8 +241,7 @@ def __getitem__(self, key):
                 return type(self)(result, name=self.name)
             # Unpack to ndarray for MPL compat
 
-            # error: "ExtensionArray" has no attribute "_data"
-            result = result._data  # type: ignore[attr-defined]
+            result = result._ndarray
 
         # Includes cases where we get a 2D ndarray back for MPL compat
         deprecate_ndim_indexing(result)
@@ -276,6 +276,12 @@ def insert(self, loc: int, item):
         # ExtensionIndex subclasses must override Index.insert
         raise AbstractMethodError(self)
 
+    def _validate_fill_value(self, value):
+        """
+        Convert value to be insertable to underlying array.
+        """
+        return self._data._validate_setitem_value(value)
+
     def _get_unique_index(self):
         if self.is_unique:
             return self
diff --git a/pandas/core/indexes/interval.py b/pandas/core/indexes/interval.py
index c2fabfc332b23..ace9b5b592900 100644
--- a/pandas/core/indexes/interval.py
+++ b/pandas/core/indexes/interval.py
@@ -1036,9 +1036,6 @@ def func(self, other, sort=sort):
 
     # --------------------------------------------------------------------
 
-    def _validate_fill_value(self, value):
-        return self._data._validate_setitem_value(value)
-
     @property
     def _is_all_dates(self) -> bool:
         """