1 files changed, 31 insertions, 0 deletions
diff --git a/src/test/ui/cross/cross-fn-cache-hole.rs b/src/test/ui/cross/cross-fn-cache-hole.rs
new file mode 100644
index 000000000..c38a5001a
--- /dev/null
+++ b/src/test/ui/cross/cross-fn-cache-hole.rs
@@ -0,0 +1,31 @@
+// Check that when there are vacuous predicates in the environment
+// (which make a fn uncallable) we don't erroneously cache those and
+// then consider them satisfied elsewhere. The current technique for
+// doing this is to not use global caches when there is a chance that
+// the environment contains such a predicate.
+// We still error for `i32: Bar<u32>` pending #48214
+
+trait Foo<X,Y>: Bar<X> {
+}
+
+trait Bar<X> { }
+
+// We don't always check where clauses for sanity, but in this case
+// wfcheck does report an error here:
+fn vacuous<A>()
+    where i32: Foo<u32, A> //~ ERROR the trait bound `i32: Bar<u32>` is not satisfied
+{
+    // ... the original intention was to check that we don't use that
+    // vacuous where clause (which could never be satisfied) to accept
+    // the following line and then mess up calls elsewhere.
+    require::<i32, u32>();
+}
+
+fn require<A,B>()
+    where A: Bar<B>
+{
+}
+
+fn main() {
+    require::<i32, u32>();
+}