error: DerefMut cannot be derived for enums. It is only applicable to structs with a single field.
  --> tests/inc/deref_mut/compile_fail_enum.rs:12:1
   |
12 | / #[ allow( dead_code ) ]
13 | | #[ derive( derive_tools_meta::DerefMut ) ]
14 | | enum MyEnum
...  |
17 | |   Variant2( i32 ),
18 | | }
   | |_^
