fix test

doc/source/whatsnew/v1.5.0.rst

@@ -511,6 +511,12 @@ Strings
 - Bug in :meth:`str.startswith` and :meth:`str.endswith` when using other series as parameter _pat_. Now raises ``TypeError`` (:issue:`3485`)
 -
 
+Merge
+^^^^^^^
+- Bug in :meth:`merge` supports complex types merge with identical columns
+-
+
+
 Interval
 ^^^^^^^^
 - Bug in :meth:`IntervalArray.__setitem__` when setting ``np.nan`` into an integer-backed array raising ``ValueError`` instead of ``TypeError`` (:issue:`45484`)

pandas/core/reshape/merge.py

@@ -2390,7 +2390,7 @@ def renamer(x, suffix):
         -------
         x : renamed column
         """
-        if x in to_rename and isinstance(x, str) and suffix is not None:
+        if x in to_rename and isinstance(x, (str, int, float)) and suffix is not None:
             return f"{x}{suffix}"
         return x
 

pandas/tests/reshape/merge/test_merge.py

@@ -2669,3 +2669,16 @@ def test_merge_different_index_names():
     result = merge(left, right, left_on="c", right_on="d")
     expected = DataFrame({"a_x": [1], "a_y": 1})
     tm.assert_frame_equal(result, expected)
+
+
+def test_merge_complex_column():
+    class Column:
+        def __init__(self, name):
+            self.name = name
+
+    merged_column = Column(name='Z')
+    left = DataFrame({merged_column: [1], 'X': [2]})
+    right = DataFrame({merged_column: [1], 'Y': [6]})
+    result = merge(left, right, left_index=True, right_index=True)
+    expected = DataFrame([[1, 2, 1, 6]], columns=[merged_column, 'X', merged_column, 'Y'])
+    tm.assert_frame_equal(result, expected)