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+`derive` was applied on something which is not a struct, a union or an enum.
+
+Erroneous code example:
+
+```compile_fail,E0774
+trait Foo {
+    #[derive(Clone)] // error!
+    type Bar;
+}
+```
+
+As said above, the `derive` attribute is only allowed on structs, unions or
+enums:
+
+```
+#[derive(Clone)] // ok!
+struct Bar {
+    field: u32,
+}
+```
+
+You can find more information about `derive` in the [Rust Book].
+
+[Rust Book]: https://doc.rust-lang.org/book/appendix-03-derivable-traits.html