box-dyn

A simple macro, here is how to use it:

#[box_dyn::box_dyn]
trait MyTrait {
    fn method_a(&self, param: usize) -> String;
    fn method_b(&mut self);
}

This will automatically implement MyTrait for Box<T: MyTrait>:

impl<T> MyTrait for Box<T> where T: MyTrait {
    fn method_a(&self, param: usize) -> String {
        MyTrait::method_a(self.as_ref(), param)
    }
    fn method_b(&mut self) {
        MyTrait::method_b(self.as_mut())
    }
}