CLN: _almost_ always rebox_native following _unbox (#37297)

Author: jbrockmendel

pandas/core/arrays/datetimelike.py

@@ -508,7 +508,8 @@ def _validate_shift_value(self, fill_value):
             )
             fill_value = new_fill
 
-        return self._unbox(fill_value)
+        rv = self._unbox(fill_value)
+        return self._rebox_native(rv)
 
     def _validate_scalar(self, value, msg: Optional[str] = None):
         """
@@ -603,18 +604,15 @@ def _validate_setitem_value(self, value):
         else:
             value = self._validate_scalar(value, msg)
 
-        return self._unbox(value, setitem=True)
+        rv = self._unbox(value, setitem=True)
+        return self._rebox_native(rv)
 
     def _validate_insert_value(self, value):
         msg = f"cannot insert {type(self).__name__} with incompatible label"
         value = self._validate_scalar(value, msg)
 
-        self._check_compatible_with(value, setitem=True)
-        # TODO: if we dont have compat, should we raise or astype(object)?
-        #  PeriodIndex does astype(object)
-        return value
-        # Note: we do not unbox here because the caller needs boxed value
-        #  to check for freq.
+        rv = self._unbox(value, setitem=True)
+        return self._rebox_native(rv)
 
     def _validate_where_value(self, other):
         msg = f"Where requires matching dtype, not {type(other)}"
@@ -623,7 +621,8 @@ def _validate_where_value(self, other):
         else:
             other = self._validate_listlike(other)
 
-        return self._unbox(other, setitem=True)
+        rv = self._unbox(other, setitem=True)
+        return self._rebox_native(rv)
 
     def _unbox(self, other, setitem: bool = False) -> Union[np.int64, np.ndarray]:
         """

pandas/core/indexes/datetimelike.py

@@ -484,7 +484,7 @@ def isin(self, values, level=None):
 
     @Appender(Index.where.__doc__)
     def where(self, cond, other=None):
-        values = self.view("i8")
+        values = self._data._ndarray
 
         try:
             other = self._data._validate_where_value(other)
@@ -493,7 +493,7 @@ def where(self, cond, other=None):
             oth = getattr(other, "dtype", other)
             raise TypeError(f"Where requires matching dtype, not {oth}") from err
 
-        result = np.where(cond, values, other).astype("i8")
+        result = np.where(cond, values, other)
         arr = self._data._from_backing_data(result)
         return type(self)._simple_new(arr, name=self.name)
 
@@ -610,7 +610,8 @@ def insert(self, loc: int, item):
         -------
         new_index : Index
         """
-        item = self._data._validate_insert_value(item)
+        value = self._data._validate_insert_value(item)
+        item = self._data._box_func(value)
 
         freq = None
         if is_period_dtype(self.dtype):
@@ -630,10 +631,8 @@ def insert(self, loc: int, item):
                     freq = self.freq
 
         arr = self._data
-        item = arr._unbox_scalar(item)
-        item = arr._rebox_native(item)
 
-        new_values = np.concatenate([arr._ndarray[:loc], [item], arr._ndarray[loc:]])
+        new_values = np.concatenate([arr._ndarray[:loc], [value], arr._ndarray[loc:]])
         new_arr = self._data._from_backing_data(new_values)
         new_arr._freq = freq