小编Pow*_*nda的帖子

我有一个Command<P>具有两个函数的特征，如下所示：

trait Client<P> {}

trait Command<P> {
    fn help(&self) -> String;
    fn exec(&self, client: &dyn Client<P>) -> String;
}

struct ListCommand {}
impl<P> Command<P> for ListCommand {
    fn help(&self) -> String {
        return "This is helptext".to_string();
    }

    fn exec(&self, client: &dyn Client<P>) -> String {
        self.help()
    }
}

fn main() {
    println!("Hello!");
}

Rust 抱怨我无法调用self.help()并exec()出现以下错误：

error[E0282]: type annotations needed
  --> src\main.rs:15:14
   |
15 |         self.help()
   |              ^^^^ cannot infer type for type parameter `P` …