How to set the trait in another trait?

Question

I tried to write two traits where you want the other to be implemented and get this error:

error[E0277]: the trait bound `T: ValTrait` is not satisfied
  --> src/main.rs:20:1
   |
20 | / fn get<T: ValRequireTrait + std::fmt::Debug>(_t: T) {
21 | |     println!("{:?}", T::VAL);
22 | | }
   | |_^ the trait `ValTrait` is not implemented for `T`
   |
   = help: consider adding a `where T: ValTrait` bound
   = note: required by `ValRequireTrait`

Code :

trait ValTrait<T = Self> {
    const VAL: T;
}

trait ValRequireTrait<T: ValTrait = Self> {}

#[derive(Debug, Copy, Clone)]
struct A {
    field: u64,
}

impl ValTrait for A {
    const VAL: A = A {
        field: 0u64
    };
}
impl ValRequireTrait for A {}


fn get<T: ValRequireTrait + std::fmt::Debug>(_t: T) {
    println!("{:?}", T::VAL);
}

fn main() {
    let a = A { field: 6u64 };
    get(a);
}

How to do it right? If I do what the compiler says, I will not need it ValRequireTrait, because it will be useless. I wanted it to ValRequireTraitbe a mark that the structure implements sufficient methods as necessary.

In other words, I expect such a requirement to be transitive, so when a function get()requires one sign ( ValRequireTrait), others ( ValTrait) will be needed automatically without any specification in the code, as the compiler wants.

Answer 1

, ValTrait supertrait ValRequireTrait. (2- ):

, , , , . - .

:

trait ValRequireTrait<T: ValTrait = Self> {}

:

trait ValRequireTrait<T: ValTrait = Self>: ValTrait<T> {}