Add non-functioning unit tests

tests/ui/derives/issue-131083.rs

@@ -0,0 +1,3 @@
+#[derive(Copy, Clone)]
+#[derive(Copy, Clone)] //~ ERROR
+enum E {}

tests/ui/derives/issue-131083.stderr

@@ -0,0 +1,21 @@
+error[E0119]: conflicting implementations of trait `Copy` for type `E`
+ --> $DIR/issue-131083.rs:2:10
+  |
+1 | #[derive(Copy, Clone)]
+  |          ---- first implementation here
+2 | #[derive(Copy, Clone)]
+  |          ^^^^ conflicting implementation for `E`
+  |
+  = note: this error originates in the derive macro `Copy` (in Nightly builds, run with -Z macro-backtrace for more info)
+
+error[E0119]: conflicting implementations of trait `Clone` for type `E`
+ --> $DIR/issue-131083.rs:2:16
+  |
+1 | #[derive(Copy, Clone)]
+  |                ----- first implementation here
+2 | #[derive(Copy, Clone)]
+  |                ^^^^^ conflicting implementation for `E`
+  |
+  = note: this error originates in the derive macro `Clone` (in Nightly builds, run with -Z macro-backtrace for more info)
+
+For more information about this error, try `rustc --explain E0119`.