add known-bug test for unsound issue 98117

Author: whtahy

tests/ui/wf/wf-in-where-clause-static.rs

@@ -0,0 +1,23 @@
+// check-pass
+// known-bug: #98117
+
+// Should fail. Functions are responsible for checking the well-formedness of
+// their own where clauses, so this should fail and require an explicit bound
+// `T: 'static`.
+
+use std::fmt::Display;
+
+trait Static: 'static {}
+impl<T> Static for &'static T {}
+
+fn foo<S: Display>(x: S) -> Box<dyn Display>
+where
+    &'static S: Static,
+{
+    Box::new(x)
+}
+
+fn main() {
+    let s = foo(&String::from("blah blah blah"));
+    println!("{}", s);
+}