diff --git a/mypy/join.py b/mypy/join.py index 0822ddbfd89a..a074fa522588 100644 --- a/mypy/join.py +++ b/mypy/join.py @@ -297,10 +297,15 @@ def visit_erased_type(self, t: ErasedType) -> ProperType: return self.s def visit_type_var(self, t: TypeVarType) -> ProperType: - if isinstance(self.s, TypeVarType) and self.s.id == t.id: - if self.s.upper_bound == t.upper_bound: - return self.s - return self.s.copy_modified(upper_bound=join_types(self.s.upper_bound, t.upper_bound)) + if isinstance(self.s, TypeVarType): + if self.s.id == t.id: + if self.s.upper_bound == t.upper_bound: + return self.s + return self.s.copy_modified( + upper_bound=join_types(self.s.upper_bound, t.upper_bound) + ) + # Fix non-commutative joins + return get_proper_type(join_types(self.s.upper_bound, t.upper_bound)) else: return self.default(self.s) diff --git a/mypy/test/testtypes.py b/mypy/test/testtypes.py index fc68d9aa6eac..f5f4c6797db2 100644 --- a/mypy/test/testtypes.py +++ b/mypy/test/testtypes.py @@ -1051,6 +1051,35 @@ def test_join_type_type_type_var(self) -> None: self.assert_join(self.fx.type_a, self.fx.t, self.fx.o) self.assert_join(self.fx.t, self.fx.type_a, self.fx.o) + def test_join_type_var_bounds(self) -> None: + tvar1 = TypeVarType( + "tvar1", + "tvar1", + TypeVarId(-100), + [], + self.fx.o, + AnyType(TypeOfAny.from_omitted_generics), + INVARIANT, + ) + any_type = AnyType(TypeOfAny.special_form) + tvar2 = TypeVarType( + "tvar2", + "tvar2", + TypeVarId(-101), + [], + upper_bound=UnionType( + [ + TupleType([any_type], self.fx.std_tuple), + TupleType([any_type, any_type], self.fx.std_tuple), + ] + ), + default=AnyType(TypeOfAny.from_omitted_generics), + variance=INVARIANT, + ) + + self.assert_join(tvar1, tvar2, self.fx.o) + self.assert_join(tvar2, tvar1, self.fx.o) + # There are additional test cases in check-inference.test. # TODO: Function types + varargs and default args.