Rename and update tests

tests/ui/derives/duplicate-derive-copy-clone-diagnostics.rs

@@ -0,0 +1,6 @@
+#[derive(Copy, Clone)]
+#[derive(Copy, Clone)]
+//~^ ERROR conflicting implementations of trait `Copy`
+enum E {}
+
+fn main() {}

tests/ui/derives/duplicate-derive-copy-clone-diagnostics.stderr

@@ -0,0 +1,23 @@
+error[E0119]: conflicting implementations of trait `Copy` for type `E`
+  --> $DIR/duplicate-derive-copy-clone-diagnostics.rs:2:10
+   |
+LL | #[derive(Copy, Clone)]
+   |          ---- first implementation here
+LL | #[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/duplicate-derive-copy-clone-diagnostics.rs:2:16
+   |
+LL | #[derive(Copy, Clone)]
+   |                ----- first implementation here
+LL | #[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)
+
+error: aborting due to 2 previous errors
+
+For more information about this error, try `rustc --explain E0119`.