1 files changed, 22 insertions, 0 deletions
diff --git a/tests/ui/traits/new-solver/prefer-candidate-no-constraints.rs b/tests/ui/traits/new-solver/prefer-candidate-no-constraints.rs
new file mode 100644
index 000000000..6f8164f3a
--- /dev/null
+++ b/tests/ui/traits/new-solver/prefer-candidate-no-constraints.rs
@@ -0,0 +1,22 @@
+// compile-flags: -Ztrait-solver=next
+// check-pass
+
+trait Foo {}
+
+impl<T> Foo for T {}
+
+trait Bar {}
+
+struct Wrapper<'a, T>(&'a T);
+
+impl<'a, T> Bar for Wrapper<'a, T> where &'a T: Foo {}
+// We need to satisfy `&'a T: Foo` when checking that this impl is WF
+// that can either be satisfied via the param-env, or via an impl.
+//
+// When satisfied via the param-env, since each lifetime is canonicalized
+// separately, we end up getting extra region constraints.
+//
+// However, when satisfied via the impl, there are no region constraints,
+// and we can short-circuit a response with no external constraints.
+
+fn main() {}