src/librustc_error_codes/error_codes/E0120.md

   1 Drop was implemented on a trait, which is not allowed: only structs and
   2 enums can implement Drop.
   3
   4 Erroneous code example:
   5
   6 ```compile_fail,E0120
   7 trait MyTrait {}
   8
   9 impl Drop for MyTrait {
  10     fn drop(&mut self) {}
  11 }
  12 ```
  13
  14 A workaround for this problem is to wrap the trait up in a struct, and implement
  15 Drop on that:
  16
  17 ```
  18 trait MyTrait {}
  19 struct MyWrapper<T: MyTrait> { foo: T }
  20
  21 impl <T: MyTrait> Drop for MyWrapper<T> {
  22     fn drop(&mut self) {}
  23 }
  24
  25 ```
  26
  27 Alternatively, wrapping trait objects requires something:
  28
  29 ```
  30 trait MyTrait {}
  31
  32 //or Box<MyTrait>, if you wanted an owned trait object
  33 struct MyWrapper<'a> { foo: &'a MyTrait }
  34
  35 impl <'a> Drop for MyWrapper<'a> {
  36     fn drop(&mut self) {}
  37 }
  38 ```