Move /src/test to /tests

tests/ui/derives/clone-debug-dead-code-in-the-same-struct.rs

@@ -0,0 +1,12 @@
+#![forbid(dead_code)]
+
+#[derive(Debug)]
+pub struct Whatever {
+    pub field0: (),
+    field1: (), //~ ERROR fields `field1`, `field2`, `field3`, and `field4` are never read
+    field2: (),
+    field3: (),
+    field4: (),
+}
+
+fn main() {}