1 files changed, 34 insertions, 0 deletions
diff --git a/src/test/ui/type-alias-impl-trait/underconstrained_lifetime.rs b/src/test/ui/type-alias-impl-trait/underconstrained_lifetime.rs
new file mode 100644
index 000000000..c5b2e8a1c
--- /dev/null
+++ b/src/test/ui/type-alias-impl-trait/underconstrained_lifetime.rs
@@ -0,0 +1,34 @@
+#![feature(type_alias_impl_trait)]
+
+use std::marker::PhantomData;
+
+trait ProofForConversion<'a, 'b> {
+    fn convert<T: ?Sized>(_: PhantomData<Self>, r: &'a T) -> &'b T;
+}
+
+impl<'a, 'b> ProofForConversion<'a, 'b> for &'b &'a () {
+    fn convert<T: ?Sized>(_: PhantomData<Self>, r: &'a T) -> &'b T {
+        r
+    }
+}
+
+type Converter<'a, 'b> = impl ProofForConversion<'a, 'b>;
+//~^ ERROR reference has a longer lifetime than the data it references
+
+// Even _defining_use with an explicit `'a: 'b` compiles fine, too.
+fn _defining_use<'a, 'b>(x: &'b &'a ()) -> Converter<'a, 'b> {
+    x
+}
+
+fn extend_lifetime<'a, 'b, T: ?Sized>(x: &'a T) -> &'b T {
+    Converter::<'a, 'b>::convert(PhantomData, x)
+}
+
+fn main() {
+    let d;
+    {
+        let x = "Hello World".to_string();
+        d = extend_lifetime(&x);
+    }
+    println!("{}", d);
+}