1 files changed, 36 insertions, 0 deletions
diff --git a/tests/ui/specialization/specialization-default-projection.rs b/tests/ui/specialization/specialization-default-projection.rs
new file mode 100644
index 00000000000..7f3ae951287
--- /dev/null
+++ b/tests/ui/specialization/specialization-default-projection.rs
@@ -0,0 +1,36 @@
+#![feature(specialization)] //~ WARN the feature `specialization` is incomplete
+
+// Make sure we can't project defaulted associated types
+
+trait Foo {
+    type Assoc;
+}
+
+impl<T> Foo for T {
+    default type Assoc = ();
+}
+
+impl Foo for u8 {
+    type Assoc = String;
+}
+
+fn generic<T>() -> <T as Foo>::Assoc {
+    // `T` could be some downstream crate type that specializes (or,
+    // for that matter, `u8`).
+
+    () //~ ERROR mismatched types
+}
+
+fn monomorphic() -> () {
+    // Even though we know that `()` is not specialized in a
+    // downstream crate, typeck refuses to project here.
+
+    generic::<()>() //~ ERROR mismatched types
+}
+
+fn main() {
+    // No error here, we CAN project from `u8`, as there is no `default`
+    // in that impl.
+    let s: String = generic::<u8>();
+    println!("{}", s); // bad news if this all compiles
+}