tests: Move run-pass tests without naming conflicts to ui

src/test/ui/structs-enums/unit-like-struct-drop-run.rs

@@ -0,0 +1,23 @@
+// run-pass
+// ignore-emscripten no threads support
+
+// Make sure the destructor is run for unit-like structs.
+
+use std::thread;
+
+struct Foo;
+
+impl Drop for Foo {
+    fn drop(&mut self) {
+        panic!("This panic should happen.");
+    }
+}
+
+pub fn main() {
+    let x = thread::spawn(move|| {
+        let _b = Foo;
+    }).join();
+
+    let s = x.unwrap_err().downcast::<&'static str>().unwrap();
+    assert_eq!(&**s, "This panic should happen.");
+}