def visit_tuple_type(self, t: TupleType) -> Type:
     if isinstance(self.s, TupleType) and self.s.length() == t.length():
         items = []  # type: List[Type]
         for i in range(t.length()):
             items.append(self.meet(t.items[i], self.s.items[i]))
         # TODO: What if the fallbacks are different?
         return TupleType(items, t.fallback)
     else:
         return self.default(self.s)

 def visit_tuple_type(self, t: TupleType) -> Type:
     if isinstance(self.s, TupleType) and self.s.length() == t.length():
         items = []  # type: List[Type]
         for i in range(t.length()):
             items.append(self.join(t.items[i], self.s.items[i]))
         fallback = join_instances(self.s.fallback, t.fallback)
         assert isinstance(fallback, Instance)
         return TupleType(items, fallback)
     else:
         return self.default(self.s)

 def visit_tuple_type(self, t: TupleType) -> Type:
     if (isinstance(self.s, TupleType) and
             cast(TupleType, self.s).length() == t.length()):
         items = [] # type: List[Type]
         for i in range(t.length()):
             items.append(self.join(t.items[i],
                                    (cast(TupleType, self.s)).items[i]))
         return TupleType(items)
     else:
         return self.default(self.s)

 def visit_tuple_type(self, t: TupleType) -> Type:
     if isinstance(self.s, TupleType) and self.s.length() == t.length():
         items = []  # type: List[Type]
         for i in range(t.length()):
             items.append(self.join(t.items[i], self.s.items[i]))
         # join fallback types if they are different
         from typing import cast
         return TupleType(items, cast(Instance, join_instances(self.s.fallback, t.fallback)))
     else:
         return self.default(self.s)

 def visit_tuple_type(self, t: TupleType) -> Type:
     if isinstance(self.s, TupleType) and self.s.length() == t.length():
         items = []  # type: List[Type]
         for i in range(t.length()):
             items.append(self.meet(t.items[i], self.s.items[i]))
         # TODO: What if the fallbacks are different?
         return TupleType(items, t.fallback)
     # meet(Tuple[t1, t2, <...>], Tuple[s, ...]) == Tuple[meet(t1, s), meet(t2, s), <...>].
     elif (isinstance(self.s, Instance) and
           self.s.type.fullname() == 'builtins.tuple' and self.s.args):
         return t.copy_modified(items=[meet_types(it, self.s.args[0]) for it in t.items])
     else:
         return self.default(self.s)

 def visit_tuple_type(self, t: TupleType) -> Type:
     if isinstance(self.s, TupleType) and self.s.length() == t.length():
         items = []  # type: List[Type]
         for i in range(t.length()):
             items.append(self.meet(t.items[i], self.s.items[i]))
         # TODO: What if the fallbacks are different?
         return TupleType(items, tuple_fallback(t))
     elif isinstance(self.s, Instance):
         # meet(Tuple[t1, t2, <...>], Tuple[s, ...]) == Tuple[meet(t1, s), meet(t2, s), <...>].
         if self.s.type.fullname() == 'builtins.tuple' and self.s.args:
             return t.copy_modified(items=[meet_types(it, self.s.args[0]) for it in t.items])
         elif is_proper_subtype(t, self.s):
             # A named tuple that inherits from a normal class
             return t
     return self.default(self.s)

 def visit_tuple_type(self, t: TupleType) -> Type:
     if isinstance(self.s, TupleType) and self.s.length() == t.length():
         items = []  # type: List[Type]
         for i in range(t.length()):
             items.append(self.meet(t.items[i], self.s.items[i]))
         # TODO: What if the fallbacks are different?
         return TupleType(items, t.fallback)
     # meet(Tuple[t1, t2, <...>], Tuple[s, ...]) == Tuple[meet(t1, s), meet(t2, s), <...>].
     elif (isinstance(self.s, Instance) and
           self.s.type.fullname() == 'builtins.tuple' and self.s.args):
         return t.copy_modified(items=[meet_types(it, self.s.args[0]) for it in t.items])
     elif (isinstance(self.s, Instance) and t.fallback.type == self.s.type):
         # Uh oh, a broken named tuple type (https://github.com/python/mypy/issues/3016).
         # Do something reasonable until that bug is fixed.
         return t
     else:
         return self.default(self.s)

 def visit_tuple_type(self, t: TupleType) -> Type:
     return t.copy_modified(items=self.expand_types(t.items))