update thomas's advice

Signed-off-by: Future-Outlier <[email protected]>

flytekit/core/type_engine.py

@@ -1915,7 +1915,11 @@ async def async_to_literal(
                 continue
 
         if is_ambiguous:
-            raise TypeError(f"Ambiguous choice of variant for union type.\n" f"Potential types: {potential_types}\n")
+            raise TypeError(
+                f"Ambiguous choice of variant for union type.\n"
+                f"Potential types: {potential_types}\n"
+                "These types are structurally the same, because it's attributes have the same names and associated types."
+            )
 
         if found_res:
             return Literal(scalar=Scalar(union=Union(value=res, stored_type=res_type)))

tests/flytekit/unit/core/test_unions.py

@@ -157,7 +157,12 @@ def t1() -> typing.Union[A, B]:
 
     with pytest.raises(
         TypeError,
-        match=("Ambiguous choice of variant for union type.\n"
-               "Potential types: \\[<class '.*\\.A'>, <class '.*\\.B'>\\]")
+        match=(
+            "Failed to convert outputs of task '.*?' at position 0\\.\n"
+            "Failed to convert type <class '.*?\\.A'> to type typing\\.Union\\[.*?\\]\\.\n"
+            "Error Message: Ambiguous choice of variant for union type\\.\n"
+            "Potential types: \\[<class '.*?\\.A'>, <class '.*?\\.B'>\\]\n"
+            "These types are structurally the same, because it's attributes have the same names and associated types\\."
+        ),
     ):
         t1()