CLN: move raising TypeError for interpolate with object dtype to …

…Block (pandas-dev#58083)

* move raising for interpolate with object dtype from NDFrame to Block

* correct msg in test_interpolate_cannot_with_object_dtype

* correct the exception message and the comments

pandas/core/generic.py

@@ -7718,11 +7718,6 @@ def interpolate(
             raise ValueError("'method' should be a string, not None.")
 
         obj, should_transpose = (self.T, True) if axis == 1 else (self, False)
-        # GH#53631
-        if np.any(obj.dtypes == object):
-            raise TypeError(
-                f"{type(self).__name__} cannot interpolate with object dtype."
-            )
 
         if isinstance(obj.index, MultiIndex) and method != "linear":
             raise ValueError(

pandas/core/internals/blocks.py

@@ -1388,12 +1388,10 @@ def interpolate(
             # If there are no NAs, then interpolate is a no-op
             return [self.copy(deep=False)]
 
-        # TODO(3.0): this case will not be reachable once GH#53638 is enforced
         if self.dtype == _dtype_obj:
-            # only deal with floats
-            # bc we already checked that can_hold_na, we don't have int dtype here
-            # test_interp_basic checks that we make a copy here
-            return [self.copy(deep=False)]
+            # GH#53631
+            name = {1: "Series", 2: "DataFrame"}[self.ndim]
+            raise TypeError(f"{name} cannot interpolate with object dtype.")
 
         copy, refs = self._get_refs_and_copy(inplace)
 

pandas/tests/series/methods/test_interpolate.py

@@ -790,11 +790,9 @@ def test_interpolate_unsorted_index(self, ascending, expected_values):
 
     def test_interpolate_asfreq_raises(self):
         ser = Series(["a", None, "b"], dtype=object)
-        msg2 = "Series cannot interpolate with object dtype"
-        msg = "Invalid fill method"
-        with pytest.raises(TypeError, match=msg2):
-            with pytest.raises(ValueError, match=msg):
-                ser.interpolate(method="asfreq")
+        msg = "Can not interpolate with method=asfreq"
+        with pytest.raises(ValueError, match=msg):
+            ser.interpolate(method="asfreq")
 
     def test_interpolate_fill_value(self):
         # GH#54920