如何在不重复方法的情况下实现结构的多个特征？

对于第二个问题（避免重复相同的实现coordinate），我想向您展示基于宏的解决方案。

有趣的是，它让您拥有3个特征而不是2个特征，因此它的方向与第一个问题的方向完全相反。我想你不可能拥有一切！:)

// factoring out the Coordinates trait from BasicInfo
trait Coordinates {
    fn coordinate(&self) -> (f64, f64);
}

// but we can require implementors of BasicInfo to also impl Coordinates
trait BasicInfo: Coordinates {
    fn area(&self) -> f64;
}

// helper macro to avoid repetition of "basic" impl Coordinates
macro_rules! impl_Coordinates { 
    ($T:ident) => {
        impl Coordinates for $T {
            fn coordinate(&self) -> (f64, f64) { (self.x, self.y) }
        }
    }
}

#[derive(Debug)]
struct Circle {
    x: f64,
    y: f64,
    radius: f64,
}

#[derive(Debug)]
struct Square {
    x: f64,
    y: f64,
    width: f64,
    sides: i32,
}

// the macro here will expand to identical implementations
// for Circle and Square. There are also more clever (but a bit
// harder to understand) ways to write the macro, so you can
// just do impl_Coordinates!(Circle, Square, Triangle, OtherShape)
// instead of repeating impl_Coordinates!
impl_Coordinates!(Circle);
impl_Coordinates!(Square);


trait Sides {
    fn has_sides(&self) -> i32;
}

impl BasicInfo for Circle {
    fn area(&self) -> f64 {
        std::f64::consts::PI * (self.radius * self.radius)
    }
}

impl BasicInfo for Square {
    fn area(&self) -> f64 {
        self.width.powf(2.0)
    }
}

impl Sides for Square {
    fn has_sides(&self) -> i32 {
        self.sides
    }
}