Handle unbound type

Author: ethframe

mypy/meet.py

@@ -7,6 +7,7 @@
     UninhabitedType, TypeType, TypeOfAny, Overloaded, FunctionLike, LiteralType,
     ProperType, get_proper_type, get_proper_types, TypeAliasType, TypeGuardType
 )
+from mypy.sametypes import is_same_type
 from mypy.subtypes import is_equivalent, is_subtype, is_callable_compatible, is_proper_subtype
 from mypy.erasetype import erase_type
 from mypy.maptype import map_instance_to_supertype
@@ -45,6 +46,8 @@ def meet_types(s: Type, t: Type) -> ProperType:
         return t
     if isinstance(s, UnionType) and not isinstance(t, UnionType):
         s, t = t, s
+    if isinstance(s, TypeVarType) and not isinstance(t, TypeVarType):
+        s, t = t, s
     return t.accept(TypeMeetVisitor(s))
 
 
@@ -483,7 +486,8 @@ def visit_erased_type(self, t: ErasedType) -> ProperType:
     def visit_type_var(self, t: TypeVarType) -> ProperType:
         if isinstance(self.s, TypeVarType) and self.s.id == t.id:
             return self.s
-        elif is_subtype(get_proper_type(t.upper_bound), self.s):
+        elif (not isinstance(self.s, UnboundType) and
+              is_same_type(t.upper_bound, meet_types(t.upper_bound, self.s))):
             return t
         else:
             return self.default(self.s)

mypy/test/testtypes.py

@@ -895,6 +895,11 @@ def test_type_vars(self) -> None:
         self.assert_meet(self.fx.s, self.fx.s, self.fx.s)
         self.assert_meet(self.fx.t, self.fx.s, NoneType())
 
+    def test_type_vars_bound(self) -> None:
+        self.assert_meet(self.fx.t, self.fx.o, self.fx.t)
+        self.assert_meet(self.fx.o, self.fx.t, self.fx.t)
+        self.assert_meet(self.fx.t, self.fx.a, NoneType())
+
     def test_none(self) -> None:
         self.assert_meet(NoneType(), NoneType(), NoneType())