Added the issue link and a test description for non-promotable-static-ref.rs

tests/ui/borrowck/non-promotable-static-ref.rs

@@ -1,3 +1,5 @@
+//Test for https://github.com/rust-lang/rust/issues/52049
+//Tests that a non-promotable temp variable cannot be used as a static reference.
 fn foo(_: &'static u32) {}
 
 fn unpromotable<T>(t: T) -> T { t }

tests/ui/borrowck/non-promotable-static-ref.stderr

@@ -1,5 +1,5 @@
 error[E0716]: temporary value dropped while borrowed
-  --> $DIR/non-promotable-static-ref.rs:6:10
+  --> $DIR/non-promotable-static-ref.rs:8:10
    |
 LL |     foo(&unpromotable(5u32));
    |     -----^^^^^^^^^^^^^^^^^^-- temporary value is freed at the end of this statement