Silence "need type annotation" from fallback

Author: sterliakov

mypy/checker.py

@@ -8485,6 +8485,11 @@ def visit_type_var(self, t: TypeVarType) -> bool:
         # multi-step type inference.
         return t.id.is_meta_var()
 
+    def visit_tuple_type(self, t: TupleType, /) -> bool:
+        # Exclude fallback to avoid bogus "need type annotation" errors
+        # TODO: Maybe erase plain tuples used as fallback in TupleType constructor?
+        return self.query_types(t.items)
+
 
 class SetNothingToAny(TypeTranslator):
     """Replace all ambiguous Uninhabited types with Any (to avoid spurious extra errors)."""

test-data/unit/check-inference.test

@@ -3886,3 +3886,10 @@ def a4(x: List[str], y: List[Never]) -> None:
     reveal_type(z2)  # N: Revealed type is "builtins.list[builtins.object]"
     z1[1].append("asdf")  # E: "object" has no attribute "append"
 [builtins fixtures/dict.pyi]
+
+[case testTupleJoinFallbackInference]
+foo = [
+    (1, ("a", "b")),
+    (2, []),
+]
+[builtins fixtures/tuple.pyi]