WARN: Remove false positive warning for iloc inplaceness

pandas/core/indexing.py

@@ -32,6 +32,7 @@
     is_array_like,
     is_bool_dtype,
     is_extension_array_dtype,
+    is_float_dtype,
     is_hashable,
     is_integer,
     is_iterator,
@@ -2016,6 +2017,8 @@ def _setitem_single_column(self, loc: int, value, plane_indexer):
                 and (
                     np.shares_memory(new_values, orig_values)
                     or new_values.shape != orig_values.shape
+                    or not is_float_dtype(orig_values)
+                    and isna(new_values).any()
                 )
             ):
                 # TODO: get something like tm.shares_memory working?

pandas/tests/frame/indexing/test_indexing.py

@@ -1326,7 +1326,8 @@ def test_loc_expand_empty_frame_keep_midx_names(self):
     def test_loc_setitem_rhs_frame(self, idxr, val):
         # GH#47578
         df = DataFrame({"a": [1, 2]})
-        df.loc[:, "a"] = DataFrame({"a": [val, 11]}, index=[1, 2])
+        with tm.assert_produces_warning(None):
+            df.loc[:, idxr] = DataFrame({"a": [val, 11]}, index=[1, 2])
         expected = DataFrame({"a": [np.nan, val]})
         tm.assert_frame_equal(df, expected)