REF: share EABackedBlock.fillna (#45425)

Author: jbrockmendel

pandas/core/internals/blocks.py

@@ -1476,6 +1476,40 @@ def putmask(self, mask, new) -> list[Block]:
 
         return [self]
 
+    def fillna(
+        self, value, limit=None, inplace: bool = False, downcast=None
+    ) -> list[Block]:
+
+        try:
+            new_values = self.values.fillna(value=value, limit=limit)
+        except (TypeError, ValueError) as err:
+            _catch_deprecated_value_error(err)
+
+            if is_interval_dtype(self.dtype):
+                # Discussion about what we want to support in the general
+                #  case GH#39584
+                blk = self.coerce_to_target_dtype(value)
+                if blk.dtype == _dtype_obj:
+                    # For now at least, only support casting e.g.
+                    #  Interval[int64]->Interval[float64],
+                    raise
+                # Never actually reached, but *could* be possible pending GH#45412
+                return blk.fillna(value, limit, inplace, downcast)
+
+            elif isinstance(self, NDArrayBackedExtensionBlock):
+                # We support filling a DatetimeTZ with a `value` whose timezone
+                #  is different by coercing to object.
+                if self.dtype.kind == "m":
+                    # TODO: don't special-case td64
+                    raise
+                blk = self.coerce_to_target_dtype(value)
+                return blk.fillna(value, limit, inplace, downcast)
+
+            else:
+                raise
+
+        return [self.make_block_same_class(values=new_values)]
+
     def delete(self, loc) -> None:
         """
         Delete given loc(-s) from block in-place.
@@ -1729,12 +1763,6 @@ def getitem_block_index(self, slicer: slice) -> ExtensionBlock:
         new_values = self.values[slicer]
         return type(self)(new_values, self._mgr_locs, ndim=self.ndim)
 
-    def fillna(
-        self, value, limit=None, inplace: bool = False, downcast=None
-    ) -> list[Block]:
-        values = self.values.fillna(value=value, limit=limit)
-        return [self.make_block_same_class(values=values)]
-
     def diff(self, n: int, axis: int = 1) -> list[Block]:
         if axis == 0 and n != 0:
             # n==0 case will be a no-op so let is fall through
@@ -1858,21 +1886,6 @@ def shift(self, periods: int, axis: int = 0, fill_value: Any = None) -> list[Blo
         new_values = values.shift(periods, fill_value=fill_value, axis=axis)
         return [self.make_block_same_class(new_values)]
 
-    def fillna(
-        self, value, limit=None, inplace: bool = False, downcast=None
-    ) -> list[Block]:
-
-        if not self._can_hold_element(value) and self.dtype.kind != "m":
-            # We support filling a DatetimeTZ with a `value` whose timezone
-            #  is different by coercing to object.
-            # TODO: don't special-case td64
-            return self.coerce_to_target_dtype(value).fillna(
-                value, limit, inplace, downcast
-            )
-
-        new_values = self.values.fillna(value=value, limit=limit)
-        return [self.make_block_same_class(values=new_values)]
-
 
 def _catch_deprecated_value_error(err: Exception) -> None:
     """