Use placeholders to prevent using inferred RPITIT types to imply their own WF-ness

2 files changed, 39 insertions, 0 deletions

diff --git a/tests/ui/impl-trait/in-trait/rpitit-hidden-types-self-implied-wf.rs b/tests/ui/impl-trait/in-trait/rpitit-hidden-types-self-implied-wf.rs
new file mode 100644
index 00000000000..c1885af4e5e
--- /dev/null
+++ b/tests/ui/impl-trait/in-trait/rpitit-hidden-types-self-implied-wf.rs
@@ -0,0 +1,23 @@
+#![feature(return_position_impl_trait_in_trait)]
+
+trait Extend {
+    fn extend(_: &str) -> (impl Sized + '_, &'static str);
+}
+
+impl Extend for () {
+    fn extend(s: &str) -> (Option<&'static &'_ ()>, &'static str) {
+        //~^ ERROR in type `&'static &()`, reference has a longer lifetime than the data it references
+        (None, s)
+    }
+}
+
+// This indirection is not necessary for reproduction,
+// but it makes this test future-proof against #114936.
+fn extend<T: Extend>(s: &str) -> &'static str {
+    <T as Extend>::extend(s).1
+}
+
+fn main() {
+    let use_after_free = extend::<()>(&String::from("temporary"));
+    println!("{}", use_after_free);
+}
diff --git a/tests/ui/impl-trait/in-trait/rpitit-hidden-types-self-implied-wf.stderr b/tests/ui/impl-trait/in-trait/rpitit-hidden-types-self-implied-wf.stderr
new file mode 100644
index 00000000000..7b63e72acbf
--- /dev/null
+++ b/tests/ui/impl-trait/in-trait/rpitit-hidden-types-self-implied-wf.stderr
@@ -0,0 +1,16 @@
+error[E0491]: in type `&'static &()`, reference has a longer lifetime than the data it references
+  --> $DIR/rpitit-hidden-types-self-implied-wf.rs:8:27
+   |
+LL |     fn extend(s: &str) -> (Option<&'static &'_ ()>, &'static str) {
+   |                           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+   = note: the pointer is valid for the static lifetime
+note: but the referenced data is only valid for the anonymous lifetime defined here
+  --> $DIR/rpitit-hidden-types-self-implied-wf.rs:8:18
+   |
+LL |     fn extend(s: &str) -> (Option<&'static &'_ ()>, &'static str) {
+   |                  ^^^^
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0491`.