Add test that statics still work

Author: samscott89

tests/tracked_fn_return_static.rs

@@ -0,0 +1,21 @@
+//! Test that a `tracked` function can return a
+//! non-`Update` type, so long as it has `'static` lifetime.
+
+use salsa::Database;
+
+#[salsa::input]
+struct Input {}
+
+#[salsa::tracked]
+fn test(_db: &dyn salsa::Database, _: Input) -> &'static str {
+    "test"
+}
+
+#[test]
+fn invoke() {
+    salsa::DatabaseImpl::new().attach(|db| {
+        let input = Input::new(db);
+        let x: &str = test(db, input);
+        assert_eq!(x, "test");
+    })
+}