Update the overlapping check for tuples to account for NamedTuples

Author: A5rocks

mypy/meet.py

@@ -50,6 +50,7 @@
     find_unpack_in_list,
     get_proper_type,
     get_proper_types,
+    is_named_instance,
     split_with_prefix_and_suffix,
 )
 
@@ -645,7 +646,18 @@ def are_tuples_overlapping(
 
     if len(left.items) != len(right.items):
         return False
-    return all(is_overlapping(l, r) for l, r in zip(left.items, right.items))
+    if not all(is_overlapping(l, r) for l, r in zip(left.items, right.items)):
+        return False
+
+    # Check that the tuples aren't from e.g. different NamedTuples.
+    if is_named_instance(right.partial_fallback, "builtins.tuple") or is_named_instance(
+        left.partial_fallback, "builtins.tuple"
+    ):
+        return True
+    else:
+        return is_subtype(left.partial_fallback, right.partial_fallback) or is_subtype(
+            right.partial_fallback, left.partial_fallback
+        )
 
 
 def expand_tuple_if_possible(tup: TupleType, target: int) -> TupleType:

test-data/unit/check-namedtuple.test

@@ -1474,3 +1474,19 @@ def main(n: NT[T]) -> None:
 
 [builtins fixtures/tuple.pyi]
 [typing fixtures/typing-namedtuple.pyi]
+
+[case testNamedTupleOverlappingCheck]
+from typing import overload, NamedTuple, Union
+
+class A(NamedTuple): ...
+
+class B(NamedTuple): ...
+
+@overload
+def f(arg: A) -> A: ...
+@overload
+def f(arg: B) -> B: ...
+def f(arg: Union[A, B]) -> Union[A, B]: ...
+
+# no errors should be raised above.
+[builtins fixtures/tuple.pyi]