Question

Given:

trait Foo
trait Bar { this: Foo => }
trait NoBar { this: Foo => }

Is there a way a can trick the type system into disallowing:

new Foo with Bar with NoBar {}

Answer 1

And type erasure saves the day again:

trait Foo
trait Dummy[A]
trait Bar extends Dummy[Bar]{ this: Foo => }
trait NoBar extends Dummy[NoBar]{ this: Foo => }
new Foo with Bar with NoBar {}

This results in the following error:

illegal inheritance; anonymous class $anon inherits different
type instances of trait Dummy: Dummy[Bar] and Dummy[NoBar]