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diff --git a/compiler/rustc_error_codes/src/error_codes/E0205.md b/compiler/rustc_error_codes/src/error_codes/E0205.md
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+#### Note: this error code is no longer emitted by the compiler.
+
+An attempt to implement the `Copy` trait for an enum failed because one of the
+variants does not implement `Copy`. To fix this, you must implement `Copy` for
+the mentioned variant. Note that this may not be possible, as in the example of
+
+```compile_fail,E0204
+enum Foo {
+    Bar(Vec<u32>),
+    Baz,
+}
+
+impl Copy for Foo { }
+```
+
+This fails because `Vec<T>` does not implement `Copy` for any `T`.
+
+Here's another example that will fail:
+
+```compile_fail,E0204
+#[derive(Copy)]
+enum Foo<'a> {
+    Bar(&'a mut bool),
+    Baz,
+}
+```
+
+This fails because `&mut T` is not `Copy`, even when `T` is `Copy` (this
+differs from the behavior for `&T`, which is always `Copy`).