Object inheritance and trait inheritance

I am researching the safety of objects with traits in rust and based on the following code snippet I have a few questions.

trait Foo {}
trait Bar : Foo {}

struct Baz;

impl Foo for Baz {}

impl Bar for Baz {}

fn do_foo(_: &Foo) {
    println!("Doing foo stuff.");
}

fn do_bar(_: &Bar) {
    println!("Doing bar tuff.");
}

fn main() {
    let x = Baz;

    let y: &Foo = &x;
    do_foo(y);

    let y: &Bar = &x;
    do_bar(y);
    // do_foo(y); -- Does not compile with mismatched types error, Expected: &Foo, found &Bar
}

      

        
        
        
      

    

• Since it Bar
  
  inherits from Foo
  
  , why is it impossible to coerce &Bar
  
  to &Foo
  
  ?
• Is there a workaround that doesn't need to be declared do_foo
  
  as generic? It is possible that it itself do_foo
  
  can exist on an object-safe basis.