src/test/ui/const-generics/type-dependent/issue-61936.rs

   1 // run-pass
   2 // revisions: full min
   3 #![cfg_attr(full, feature(const_generics))]
   4 #![cfg_attr(full, allow(incomplete_features))]
   5 #![cfg_attr(min, feature(min_const_generics))]
   6
   7 trait SliceExt<T: Clone> {
   8     fn array_windows_example<'a, const N: usize>(&'a self) -> ArrayWindowsExample<'a, T, N>;
   9 }
  10
  11 impl <T: Clone> SliceExt<T> for [T] {
  12    fn array_windows_example<'a, const N: usize>(&'a self) -> ArrayWindowsExample<'a, T, N> {
  13        ArrayWindowsExample{ idx: 0, slice: &self }
  14    }
  15 }
  16
  17 struct ArrayWindowsExample<'a, T, const N: usize> {
  18     slice: &'a [T],
  19     idx: usize,
  20 }
  21
  22 impl <'a, T: Clone, const N: usize> Iterator for ArrayWindowsExample<'a, T, N> {
  23     type Item = [T; N];
  24     fn next(&mut self) -> Option<Self::Item> {
  25         // Note: this is unsound for some `T` and not meant as an example
  26         // on how to implement `ArrayWindows`.
  27         let mut res = unsafe{ std::mem::zeroed() };
  28         let mut ptr = &mut res as *mut [T; N] as *mut T;
  29
  30         for i in 0..N {
  31             match self.slice[self.idx..].get(i) {
  32                 None => return None,
  33                 Some(elem) => unsafe { std::ptr::write_volatile(ptr, elem.clone())},
  34             };
  35             ptr = ptr.wrapping_add(1);
  36             self.idx += 1;
  37         }
  38
  39         Some(res)
  40     }
  41 }
  42
  43 const FOUR: usize = 4;
  44
  45 fn main() {
  46     let v: Vec<usize> = vec![0; 100];
  47
  48     for array in v.as_slice().array_windows_example::<FOUR>() {
  49         assert_eq!(array, [0, 0, 0, 0])
  50     }
  51 }