1 files changed, 21 insertions, 0 deletions
diff --git a/tests/ui/coherence/normalize-for-errors.rs b/tests/ui/coherence/normalize-for-errors.rs
new file mode 100644
index 000000000..30723518b
--- /dev/null
+++ b/tests/ui/coherence/normalize-for-errors.rs
@@ -0,0 +1,21 @@
+// revisions: current next
+//[next] compile-flags: -Znext-solver
+
+struct MyType;
+trait MyTrait<S> {}
+
+trait Mirror {
+    type Assoc;
+}
+impl<T> Mirror for T {
+    type Assoc = T;
+}
+
+impl<T: Copy, S: Iterator> MyTrait<S> for (T, S::Item) {}
+//~^ NOTE first implementation here
+impl<S: Iterator> MyTrait<S> for (Box<<(MyType,) as Mirror>::Assoc>, S::Item) {}
+//~^ ERROR conflicting implementations of trait `MyTrait<_>` for type `(Box<(MyType,)>,
+//~| NOTE conflicting implementation for `(Box<(MyType,)>,
+//~| NOTE upstream crates may add a new impl of trait `std::marker::Copy` for type `std::boxed::Box<(MyType,)>` in future versions
+
+fn main() {}