scala> object foo { class Foo }
// defined object foo
scala> object bar { class Foo }
// defined object bar
scala> implicit def eqFoo: CanEqual[foo.Foo, foo.Foo] = CanEqual.derived
def eqFoo: CanEqual[foo.Foo, foo.Foo]
scala> object Bar { new foo.Foo == new bar.Foo }
-- [E172] Type Error: ----------------------------------------------------------
1 |object Bar { new foo.Foo == new bar.Foo }
  |             ^^^^^^^^^^^^^^^^^^^^^^^^^^
  |     Values of types foo.Foo and bar.Foo² cannot be compared with == or !=
  |
  |     where:    Foo  is a class in object foo
  |               Foo² is a class in object bar
1 error found
