src/test/ui/lang-items/lang-item-generic-requirements.rs

   1 // Checks that declaring a lang item with the wrong number
   2 // of generic arguments errors rather than crashing (issue #83893, #87573, part of #9307, #79559).
   3
   4 #![feature(lang_items, no_core)]
   5 #![no_core]
   6
   7 #[lang = "sized"]
   8 trait MySized {}
   9
  10 #[lang = "add"]
  11 trait MyAdd<'a, T> {}
  12 //~^^ ERROR: `add` language item must be applied to a trait with 1 generic argument [E0718]
  13
  14 #[lang = "drop_in_place"]
  15 //~^ ERROR `drop_in_place` language item must be applied to a function with at least 1 generic
  16 fn my_ptr_drop() {}
  17
  18 #[lang = "index"]
  19 trait MyIndex<'a, T> {}
  20 //~^^ ERROR: `index` language item must be applied to a trait with 1 generic argument [E0718]
  21
  22 #[lang = "phantom_data"]
  23 //~^ ERROR `phantom_data` language item must be applied to a struct with 1 generic argument
  24 struct MyPhantomData<T, U>;
  25 //~^ ERROR parameter `T` is never used
  26 //~| ERROR parameter `U` is never used
  27
  28 // When the `start` lang item is missing generics very odd things can happen, especially when
  29 // it comes to cross-crate monomorphization
  30 #[lang = "start"]
  31 //~^ ERROR `start` language item must be applied to a function with 1 generic argument [E0718]
  32 fn start(_: *const u8, _: isize, _: *const *const u8) -> isize {
  33     0
  34 }
  35
  36 fn ice() {
  37     // Use add
  38     let r = 5;
  39     let a = 6;
  40     r + a;
  41
  42     // Use drop in place
  43     my_ptr_drop();
  44
  45     // Use index
  46     let arr = [0; 5];
  47     let _ = arr[2];
  48
  49     // Use phantomdata
  50     let _ = MyPhantomData::<(), i32>;
  51 }
  52
  53 // use `start`
  54 fn main() {}