1 files changed, 55 insertions, 0 deletions

diff --git a/tests/ui/issues/issue-3743.rs b/tests/ui/issues/issue-3743.rs
new file mode 100644
index 000000000..07741914f
--- /dev/null
+++ b/tests/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
+}