尝试实现supertrait中声明的函数时出错

我试图实现一种具有超特质的特质,比如:

trait A {
    fn do_a(&self);
}

trait B: A {
    fn do_b(&self);
}

struct S {}

impl B for S {
    fn do_a(&self) {}
    fn do_b(&self) {}
}

error[E0407]: method `do_a` is not a member of trait `B`
  --> src/example.rs:12:5
   |
12 |     fn do_a(&self) {}
   |     ^^^^^^^^^^^^^^^^^ not a member of trait `B`

error[E0277]: the trait bound `example::S: example::A` is not satisfied
  --> src/example.rs:11:6
   |
5  | trait B: A {
   |          - required by this bound in `example::B`
...
11 | impl B for S {
   |      ^ the trait `example::A` is not implemented for `example::S`

我一直在重读有关超级特质的文章,但我很难理解这个错误。

• trait B: A
• do_a(&self) {} A .