REGR: fix inplace operations for EAs with non-EA arg

pandas/core/generic.py

@@ -70,6 +70,7 @@
     is_datetime64_any_dtype,
     is_datetime64tz_dtype,
     is_dict_like,
+    is_dtype_equal,
     is_extension_array_dtype,
     is_float,
     is_list_like,
@@ -11266,7 +11267,11 @@ def _inplace_method(self, other, op):
         """
         result = op(self, other)
 
-        if self.ndim == 1 and result._indexed_same(self) and result.dtype == self.dtype:
+        if (
+            self.ndim == 1
+            and result._indexed_same(self)
+            and is_dtype_equal(result.dtype, self.dtype)
+        ):
             # GH#36498 this inplace op can _actually_ be inplace.
             self._values[:] = result._values
             return self

pandas/tests/series/methods/test_inplace_ops.py

@@ -0,0 +1,60 @@
+import pytest
+
+from pandas import Series
+import pandas._testing as tm
+
+
+@pytest.mark.parametrize(
+    "ser1, ser2, expected_add, expected_sub, expected_mul",
+    (
+        [
+            Series([1], dtype="Int64"),
+            Series([2], dtype="Int64"),
+            Series([3], dtype="Int64"),
+            Series([-1], dtype="Int64"),
+            Series([2], dtype="Int64"),
+        ],
+        [
+            Series([1], dtype="float"),
+            Series([2.0], dtype="float"),
+            Series([3.0], dtype="float"),
+            Series([-1.0], dtype="float"),
+            Series([2.0], dtype="float"),
+        ],
+        [
+            Series([1], dtype="Int64"),
+            Series([2.0], dtype="float"),
+            Series([3.0], dtype="float"),
+            Series([-1.0], dtype="float"),
+            Series([2], dtype="float"),
+        ],
+        [
+            Series([1.0], dtype="float"),
+            Series([2], dtype="Int64"),
+            Series([3.0], dtype="float"),
+            Series([-1.0], dtype="float"),
+            Series([2], dtype="float"),
+        ],
+        pytest.param(
+            Series([1], dtype="Int64"),
+            Series([2.0], dtype="Float64"),
+            Series([3.0], dtype="Float64"),
+            Series([-1.0], dtype="Float64"),
+            Series([2], dtype="Float64"),
+            marks=pytest.mark.xfail(reason="Not implemented yet"),
+        ),
+    ),
+)
+def test_series_inplace_ops(ser1, ser2, expected_add, expected_sub, expected_mul):
+
+    res = ser1.copy()
+    res += ser2
+    tm.assert_series_equal(res, expected_add)
+
+    res = ser1.copy()
+    res -= ser2
+    tm.assert_series_equal(res, expected_sub)
+
+    res = ser1.copy()
+    res *= ser2
+    tm.assert_series_equal(res, expected_mul)