From 6f9041bd1572239bec2d8653b84ea4ddd2a7d22d Mon Sep 17 00:00:00 2001
From: lcnr <rust@lcnr.de>
Date: Tue, 23 May 2023 19:34:17 +0200
Subject: [PATCH] add the leak check to the new solver

---
 .../src/solve/eval_ctxt/canonical.rs          |  5 ++++
 .../higher-ranked/leak-check-in-selection.rs  | 24 +++++++++++++++++++
 2 files changed, 29 insertions(+)
 create mode 100644 tests/ui/higher-ranked/leak-check-in-selection.rs

diff --git a/compiler/rustc_trait_selection/src/solve/eval_ctxt/canonical.rs b/compiler/rustc_trait_selection/src/solve/eval_ctxt/canonical.rs
index fdb209fbff87..91a093f30bd5 100644
--- a/compiler/rustc_trait_selection/src/solve/eval_ctxt/canonical.rs
+++ b/compiler/rustc_trait_selection/src/solve/eval_ctxt/canonical.rs
@@ -137,6 +137,11 @@ impl<'tcx> EvalCtxt<'_, 'tcx> {
 
     #[instrument(level = "debug", skip(self), ret)]
     fn compute_external_query_constraints(&self) -> Result<ExternalConstraints<'tcx>, NoSolution> {
+        self.infcx.leak_check(ty::UniverseIndex::ROOT, None).map_err(|e| {
+            debug!(?e, "failed the leak check");
+            NoSolution
+        })?;
+
         // Cannot use `take_registered_region_obligations` as we may compute the response
         // inside of a `probe` whenever we have multiple choices inside of the solver.
         let region_obligations = self.infcx.inner.borrow().region_obligations().to_owned();
diff --git a/tests/ui/higher-ranked/leak-check-in-selection.rs b/tests/ui/higher-ranked/leak-check-in-selection.rs
new file mode 100644
index 000000000000..e8d6cff856c9
--- /dev/null
+++ b/tests/ui/higher-ranked/leak-check-in-selection.rs
@@ -0,0 +1,24 @@
+// run-pass
+// revisions: old next
+//[next] compile-flags: -Ztrait-solver=next
+#![allow(coherence_leak_check)]
+
+trait Trait: Sized {
+    fn is_higher_ranked(self) -> bool;
+}
+
+impl Trait for for<'a> fn(&'a ()) {
+    fn is_higher_ranked(self) -> bool {
+        true
+    }
+}
+impl<'a> Trait for fn(&'a ()) {
+    fn is_higher_ranked(self) -> bool {
+        false
+    }
+}
+
+fn main() {
+    let x: for<'a> fn(&'a ()) = |&()| ();
+    assert!(x.is_higher_ranked());
+}