diff options
Diffstat (limited to '')
-rw-r--r-- | src/test/ui/issues/issue-3743.rs | 55 |
1 files changed, 55 insertions, 0 deletions
diff --git a/src/test/ui/issues/issue-3743.rs b/src/test/ui/issues/issue-3743.rs new file mode 100644 index 000000000..07741914f --- /dev/null +++ b/src/test/ui/issues/issue-3743.rs @@ -0,0 +1,55 @@ +// 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 +} |