fix various issues reported by the CI

Author: topper-123

pandas/core/indexes/base.py

@@ -358,7 +358,7 @@ def _outer_indexer(
     _comparables = ["name"]
     _attributes = ["name"]
     _is_numeric_dtype = False
-    _can_hold_na = True
+    _can_hold_na: bool = True
     _can_hold_strings = True
 
     # would we like our indexing holder to defer to us

pandas/core/indexes/numeric.py

@@ -16,7 +16,10 @@
     Dtype,
     DtypeObj,
 )
-from pandas.util._decorators import doc
+from pandas.util._decorators import (
+    cache_readonly,
+    doc,
+)
 
 from pandas.core.dtypes.cast import astype_nansafe
 from pandas.core.dtypes.common import (
@@ -382,7 +385,7 @@ class NumIndex(NumericIndex):
     _default_dtype: np.dtype
     _dtype_validation_metadata = (is_numeric_dtype, "numeric type")
 
-    @property
+    @cache_readonly
     def _can_hold_na(self) -> bool:
         if is_integer_dtype(self.dtype):
             return False

pandas/tests/base/test_unique.py

@@ -24,6 +24,9 @@ def test_unique(index_or_series_obj):
         expected = pd.MultiIndex.from_tuples(unique_values)
         expected.names = obj.names
         tm.assert_index_equal(result, expected)
+    elif isinstance(obj, pd.NumIndex):
+        expected = pd.NumIndex(unique_values, dtype=obj.dtype)
+        tm.assert_index_equal(result, expected)
     elif isinstance(obj, pd.Index):
         expected = pd.Index(unique_values, dtype=obj.dtype)
         if is_datetime64tz_dtype(obj.dtype):
@@ -62,7 +65,10 @@ def test_unique_null(null_obj, index_or_series_obj):
     unique_values_not_null = [val for val in unique_values_raw if not pd.isnull(val)]
     unique_values = [null_obj] + unique_values_not_null
 
-    if isinstance(obj, pd.Index):
+    if isinstance(obj, pd.NumIndex):
+        expected = pd.NumIndex(unique_values, dtype=obj.dtype)
+        tm.assert_index_equal(result, expected)
+    elif isinstance(obj, pd.Index):
         expected = pd.Index(unique_values, dtype=obj.dtype)
         if is_datetime64tz_dtype(obj.dtype):
             result = result.normalize()