1 files changed, 115 insertions, 0 deletions
diff --git a/src/test/ui/traits/trait-upcasting/diamond.rs b/src/test/ui/traits/trait-upcasting/diamond.rs
new file mode 100644
index 000000000..e4e23c1a2
--- /dev/null
+++ b/src/test/ui/traits/trait-upcasting/diamond.rs
@@ -0,0 +1,115 @@
+// run-pass
+
+#![feature(trait_upcasting)]
+#![allow(incomplete_features)]
+
+trait Foo: PartialEq<i32> + std::fmt::Debug + Send + Sync {
+    fn a(&self) -> i32 {
+        10
+    }
+
+    fn z(&self) -> i32 {
+        11
+    }
+
+    fn y(&self) -> i32 {
+        12
+    }
+}
+
+trait Bar1: Foo {
+    fn b(&self) -> i32 {
+        20
+    }
+
+    fn w(&self) -> i32 {
+        21
+    }
+}
+
+trait Bar2: Foo {
+    fn c(&self) -> i32 {
+        30
+    }
+
+    fn v(&self) -> i32 {
+        31
+    }
+}
+
+trait Baz: Bar1 + Bar2 {
+    fn d(&self) -> i32 {
+        40
+    }
+}
+
+impl Foo for i32 {
+    fn a(&self) -> i32 {
+        100
+    }
+}
+
+impl Bar1 for i32 {
+    fn b(&self) -> i32 {
+        200
+    }
+}
+
+impl Bar2 for i32 {
+    fn c(&self) -> i32 {
+        300
+    }
+}
+
+impl Baz for i32 {
+    fn d(&self) -> i32 {
+        400
+    }
+}
+
+fn main() {
+    let baz: &dyn Baz = &1;
+    let _: &dyn std::fmt::Debug = baz;
+    assert_eq!(*baz, 1);
+    assert_eq!(baz.a(), 100);
+    assert_eq!(baz.b(), 200);
+    assert_eq!(baz.c(), 300);
+    assert_eq!(baz.d(), 400);
+    assert_eq!(baz.z(), 11);
+    assert_eq!(baz.y(), 12);
+    assert_eq!(baz.w(), 21);
+    assert_eq!(baz.v(), 31);
+
+    let bar1: &dyn Bar1 = baz;
+    let _: &dyn std::fmt::Debug = bar1;
+    assert_eq!(*bar1, 1);
+    assert_eq!(bar1.a(), 100);
+    assert_eq!(bar1.b(), 200);
+    assert_eq!(bar1.z(), 11);
+    assert_eq!(bar1.y(), 12);
+    assert_eq!(bar1.w(), 21);
+
+    let bar2: &dyn Bar2 = baz;
+    let _: &dyn std::fmt::Debug = bar2;
+    assert_eq!(*bar2, 1);
+    assert_eq!(bar2.a(), 100);
+    assert_eq!(bar2.c(), 300);
+    assert_eq!(bar2.z(), 11);
+    assert_eq!(bar2.y(), 12);
+    assert_eq!(bar2.v(), 31);
+
+    let foo: &dyn Foo = baz;
+    let _: &dyn std::fmt::Debug = foo;
+    assert_eq!(*foo, 1);
+    assert_eq!(foo.a(), 100);
+
+    let foo: &dyn Foo = bar1;
+    let _: &dyn std::fmt::Debug = foo;
+    assert_eq!(*foo, 1);
+    assert_eq!(foo.a(), 100);
+
+    let foo: &dyn Foo = bar2;
+    let _: &dyn std::fmt::Debug = foo;
+    assert_eq!(*foo, 1);
+    assert_eq!(foo.a(), 100);
+}