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+The `Copy` trait was implemented on a type which contains a field that doesn't
+implement the `Copy` trait.
+
+Erroneous code example:
+
+```compile_fail,E0204
+struct Foo {
+    foo: Vec<u32>,
+}
+
+impl Copy for Foo { } // error!
+```
+
+The `Copy` trait is implemented by default only on primitive types. If your
+type only contains primitive types, you'll be able to implement `Copy` on it.
+Otherwise, it won't be possible.
+
+Here's another example that will fail:
+
+```compile_fail,E0204
+#[derive(Copy)] // error!
+struct Foo<'a> {
+    ty: &'a mut bool,
+}
+```
+
+This fails because `&mut T` is not `Copy`, even when `T` is `Copy` (this
+differs from the behavior for `&T`, which is always `Copy`).