1 files changed, 44 insertions, 0 deletions
diff --git a/tests/ui/sanitizer/cfi-can-reveal-opaques.rs b/tests/ui/sanitizer/cfi-can-reveal-opaques.rs
new file mode 100644
index 00000000000..55988a62a8c
--- /dev/null
+++ b/tests/ui/sanitizer/cfi-can-reveal-opaques.rs
@@ -0,0 +1,44 @@
+//@ needs-sanitizer-cfi
+//@ compile-flags: -Ccodegen-units=1 -Clto -Ctarget-feature=-crt-static -Zsanitizer=cfi
+//@ no-prefer-dynamic
+//@ only-x86_64-unknown-linux-gnu
+//@ build-pass
+
+// See comment below for why this test exists.
+
+trait Tr<U> {
+    type Projection;
+}
+
+impl<F, U> Tr<U> for F
+where
+    F: Fn() -> U
+{
+    type Projection = U;
+}
+
+fn test<B: Tr<U>, U>(b: B) -> B::Projection
+{
+    todo!()
+}
+
+fn main() {
+    fn rpit_fn() -> impl Sized {}
+
+    // When CFI runs, it tries to compute the signature of the call. This
+    // ends up giving us a signature of:
+    //     `fn test::<rpit_fn, ()>() -> <rpit_fn as Tr<()>>::Projection`,
+    // where `rpit_fn` is the ZST FnDef for the function. However, we were
+    // previously using a Reveal::UserFacing param-env. This means that the
+    // `<rpit_fn as Tr<()>>::Projection` return type is impossible to normalize,
+    // since it would require proving `rpit_fn: Fn() -> ()`, but we cannot
+    // prove that the `impl Sized` opaque is `()` with a user-facing param-env.
+    // This leads to a normalization error, and then an ICE.
+    //
+    // Side-note:
+    // So why is the second generic of `test` "`()`", and not the
+    // `impl Sized` since we inferred it from the return type of `rpit_fn`
+    // during typeck? Well, that's because we're using the generics from the
+    // terminator of the MIR, which has had the RevealAll pass performed on it.
+    let _ = test(rpit_fn);
+}