trait Foo {}
trait Baz : Foo {
    fn baz();
}

struct A;
struct B;
struct C;

impl Foo for A {}
impl Foo for B {}
impl Foo for C {}

impl Baz for A {
    fn baz() {}
}
impl Baz for B {
    fn baz() {}
}

struct PlatformDependent<F: Foo>(F);

impl<F: Baz> PlatformDependent<F>
where
{
    fn bar() {
        F::baz();
    }
}

/* No implementation for Platform  C */