compiler/rustc_error_codes/src/error_codes/E0152.md

   1 A lang item was redefined.
   2
   3 Erroneous code example:
   4
   5 ```compile_fail,E0152
   6 #![feature(lang_items)]
   7
   8 #[lang = "owned_box"]
   9 struct Foo<T>(T); // error: duplicate lang item found: `owned_box`
  10 ```
  11
  12 Lang items are already implemented in the standard library. Unless you are
  13 writing a free-standing application (e.g., a kernel), you do not need to provide
  14 them yourself.
  15
  16 You can build a free-standing crate by adding `#![no_std]` to the crate
  17 attributes:
  18
  19 ```ignore (only-for-syntax-highlight)
  20 #![no_std]
  21 ```
  22
  23 See also the [unstable book][1].
  24
  25 [1]: https://doc.rust-lang.org/unstable-book/language-features/lang-items.html#writing-an-executable-without-stdlib