Revert " BUG: RecursionError when attempting to replace np.nan values (pandas-dev#45725) (pandas-dev#45749)" (pandas-dev#46403)

This reverts commit d0a687c.

Author: simonjayhawkins

pandas/core/internals/blocks.py

@@ -568,7 +568,6 @@ def replace(
         #  go through replace_list
 
         values = self.values
-        value = self._standardize_fill_value(value)  # GH#45725
 
         if isinstance(values, Categorical):
             # TODO: avoid special-casing

pandas/tests/frame/methods/test_replace.py

@@ -661,21 +661,6 @@ def test_replace_simple_nested_dict_with_nonexistent_value(self):
         result = df.replace({"col": {-1: "-", 1: "a", 4: "b"}})
         tm.assert_frame_equal(expected, result)
 
-    def test_replace_numpy_nan(self, nulls_fixture):
-        # GH#45725 ensure numpy.nan can be replaced with all other null types
-        to_replace = np.nan
-        value = nulls_fixture
-        dtype = object
-        df = DataFrame({"A": [to_replace]}, dtype=dtype)
-        expected = DataFrame({"A": [value]}, dtype=dtype)
-
-        result = df.replace({to_replace: value}).astype(dtype=dtype)
-        tm.assert_frame_equal(result, expected)
-
-        # same thing but different calling convention
-        result = df.replace(to_replace, value).astype(dtype=dtype)
-        tm.assert_frame_equal(result, expected)
-
     def test_replace_value_is_none(self, datetime_frame):
         orig_value = datetime_frame.iloc[0, 0]
         orig2 = datetime_frame.iloc[1, 0]

pandas/tests/series/methods/test_replace.py

@@ -36,23 +36,6 @@ def test_replace_explicit_none(self):
         assert expected.iloc[-1] is None
         tm.assert_series_equal(result, expected)
 
-    def test_replace_numpy_nan(self, nulls_fixture):
-        # GH#45725 ensure numpy.nan can be replaced with all other null types
-        to_replace = np.nan
-        value = nulls_fixture
-        dtype = object
-        ser = pd.Series([to_replace], dtype=dtype)
-        expected = pd.Series([value], dtype=dtype)
-
-        result = ser.replace({to_replace: value}).astype(dtype=dtype)
-        tm.assert_series_equal(result, expected)
-        assert result.dtype == dtype
-
-        # same thing but different calling convention
-        result = ser.replace(to_replace, value).astype(dtype=dtype)
-        tm.assert_series_equal(result, expected)
-        assert result.dtype == dtype
-
     def test_replace_noop_doesnt_downcast(self):
         # GH#44498
         ser = pd.Series([None, None, pd.Timestamp("2021-12-16 17:31")], dtype=object)