mirror of
https://github.com/rust-lang/rust.git
synced 2024-12-05 05:04:24 +00:00
56 lines
1.3 KiB
Rust
56 lines
1.3 KiB
Rust
// run-pass
|
|
// If `Mul` used an associated type for its output, this test would
|
|
// work more smoothly.
|
|
|
|
use std::ops::Mul;
|
|
|
|
#[derive(Copy, Clone)]
|
|
struct Vec2 {
|
|
x: f64,
|
|
y: f64
|
|
}
|
|
|
|
// methods we want to export as methods as well as operators
|
|
impl Vec2 {
|
|
#[inline(always)]
|
|
fn vmul(self, other: f64) -> Vec2 {
|
|
Vec2 { x: self.x * other, y: self.y * other }
|
|
}
|
|
}
|
|
|
|
// Right-hand-side operator visitor pattern
|
|
trait RhsOfVec2Mul {
|
|
type Result;
|
|
|
|
fn mul_vec2_by(&self, lhs: &Vec2) -> Self::Result;
|
|
}
|
|
|
|
// Vec2's implementation of Mul "from the other side" using the above trait
|
|
impl<Res, Rhs: RhsOfVec2Mul<Result=Res>> Mul<Rhs> for Vec2 {
|
|
type Output = Res;
|
|
|
|
fn mul(self, rhs: Rhs) -> Res { rhs.mul_vec2_by(&self) }
|
|
}
|
|
|
|
// Implementation of 'f64 as right-hand-side of Vec2::Mul'
|
|
impl RhsOfVec2Mul for f64 {
|
|
type Result = Vec2;
|
|
|
|
fn mul_vec2_by(&self, lhs: &Vec2) -> Vec2 { lhs.vmul(*self) }
|
|
}
|
|
|
|
// Usage with failing inference
|
|
pub fn main() {
|
|
let a = Vec2 { x: 3.0f64, y: 4.0f64 };
|
|
|
|
// the following compiles and works properly
|
|
let v1: Vec2 = a * 3.0f64;
|
|
println!("{} {}", v1.x, v1.y);
|
|
|
|
// the following compiles but v2 will not be Vec2 yet and
|
|
// using it later will cause an error that the type of v2
|
|
// must be known
|
|
let v2 = a * 3.0f64;
|
|
println!("{} {}", v2.x, v2.y); // error regarding v2's type
|
|
}
|