rust - 可以在Rust中使用通用类型的特征对象吗？

Question

我对如何使用Rust的trait对象感到困惑。我有很多模糊的部分理解，但最终我不明白我得到的错误。
我正在尝试在rust中实现命令模式，以便在终端上移动光标。我设置它来发送实现Command特征的特征对象，并通用键入Command特征。我不能使这个特性通用吗？
这是我的代码的示例版本:

pub trait Command<T> {
    fn execute(&self, target_instance: &mut T);
}

pub trait Commandable<T> {
    fn send(&mut self, cmd: Box<impl Command<T>>);
}
//-------------------------------------------------------

struct Cursor {
    pos: (isize, isize),
}

impl Cursor {
    fn move_me(&mut self, direction: (isize, isize)) {
        self.pos.0 += direction.0;
        self.pos.1 += direction.1;
    }
}

impl Commandable<Cursor> for Cursor {
    fn send(&mut self, cmd: Box<impl Command<Cursor>>) {
        cmd.execute(self);
    }
}

struct MoveCommand {
    move_direction: (isize, isize),
}

impl MoveCommand {
    pub fn new(move_direction: (isize, isize)) -> Self {
        MoveCommand { move_direction }
    }
}

impl Command<Cursor> for MoveCommand {
    fn execute(&self, cursor: &mut Cursor) {
        cursor.move_me(self.move_direction);
    }
}
//------------------------------------------------------

fn handle_input(input: Option<&str>, target: &mut impl Commandable<Cursor>) {
    let mut cmd: Option<Box<dyn Command<Cursor>>> = None;
    if let Some(key) = input {
        match key {
            "K" => cmd = Some(Box::new(MoveCommand::new( (0, -1) ))),
            "J" => cmd = Some(Box::new(MoveCommand::new( (0, 1) ))),
            "H" => cmd = Some(Box::new(MoveCommand::new( (-1, 0) ))),
            "L" => cmd = Some(Box::new(MoveCommand::new( (1, 0) ))),
            _ => {}
        }
    }
    if let Some(boxed_cmd) = cmd {
        target.send(boxed_cmd); // <-----------------ERROR IS HERE
    }
}

fn main() {
    let mut cursor = Cursor { pos: (0, 0) };
    handle_input(Some("K"), &mut cursor);
}

这是错误:

error[E0277]: the size for values of type `dyn Command<Cursor>` cannot be known at compilation time
  --> src/main.rs:54:21
   |
54 |         target.send(boxed_cmd);
   |                     ^^^^^^^^^ doesn't have a size known at compile-time
   |
   = help: the trait `Sized` is not implemented for `dyn Command<Cursor>`

Answer 1

回答我自己的问题以帮助 future 的人们:
我的主要问题是我不了解dyn MyTraitObj和impl MyTraitObj之间的区别。我可以互换使用它们，所以一旦将所有impl交换为dyn，我发布的代码就会被编译。
@LeoVen对此进行了链接，这为我解决了困惑:What is the difference between trait and impl trait when used as method arguments?
感谢所有提供帮助的人。