tests/ui/const-generics/type-dependent/issue-61936.rs

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