1 files changed, 35 insertions, 0 deletions
diff --git a/src/test/ui/implied-bounds/hrlt-implied-trait-bounds-roundtrip.rs b/src/test/ui/implied-bounds/hrlt-implied-trait-bounds-roundtrip.rs
new file mode 100644
index 000000000..69847d6a8
--- /dev/null
+++ b/src/test/ui/implied-bounds/hrlt-implied-trait-bounds-roundtrip.rs
@@ -0,0 +1,35 @@
+// check-pass
+struct Foo<'a>(&'a ())
+where
+    (): Trait<'a>;
+
+trait Trait<'a> {
+    fn id<T>(value: &'a T) -> &'static T;
+}
+
+impl Trait<'static> for () {
+    fn id<T>(value: &'static T) -> &'static T {
+        value
+    }
+}
+
+fn could_use_implied_bounds<'a, T>(_: Foo<'a>, x: &'a T) -> &'static T
+where
+    (): Trait<'a>, // This could be an implied bound
+{
+    <()>::id(x)
+}
+
+fn main() {
+    let bar: for<'a, 'b> fn(Foo<'a>, &'b ()) = |_, _| {};
+
+    // If `could_use_implied_bounds` were to use implied bounds,
+    // keeping 'a late-bound, then we could assign that function
+    // to this variable.
+    let bar: for<'a> fn(Foo<'a>, &'a ()) = bar;
+
+    // In this case, the subtyping relation here would be unsound,
+    // allowing us to transmute lifetimes. This currently compiles
+    // because we incorrectly deal with implied bounds inside of binders.
+    let _bar: for<'a, 'b> fn(Foo<'a>, &'b ()) = bar;
+}