1 files changed, 17 insertions, 0 deletions
diff --git a/src/test/ui/type/type-parameter-defaults-referencing-Self-ppaux.rs b/src/test/ui/type/type-parameter-defaults-referencing-Self-ppaux.rs
new file mode 100644
index 000000000..444453dc6
--- /dev/null
+++ b/src/test/ui/type/type-parameter-defaults-referencing-Self-ppaux.rs
@@ -0,0 +1,17 @@
+// Test a default that references `Self` which is then used in an
+// object type. Issue #18956. In this case, the value is supplied by
+// the user, but pretty-printing the type during the error message
+// caused an ICE.
+
+trait MyAdd<Rhs=Self> { fn add(&self, other: &Rhs) -> Self; }
+
+impl MyAdd for i32 {
+    fn add(&self, other: &i32) -> i32 { *self + *other }
+}
+
+fn main() {
+    let x: i32 = 5;
+    let y = x as dyn MyAdd<i32>;
+    //~^ ERROR E0038
+    //~| ERROR cast to unsized type: `i32` as `dyn MyAdd<i32>`
+}