diff --git a/src/test/ui/const-generics/type-dependent/issue-71805.rs b/src/test/ui/const-generics/type-dependent/issue-71805.rs new file mode 100644 index 0000000000000..6823d780aefa9 --- /dev/null +++ b/src/test/ui/const-generics/type-dependent/issue-71805.rs @@ -0,0 +1,41 @@ +// run-pass +#![feature(const_generics)] +#![allow(incomplete_features)] + +use std::mem::MaybeUninit; + +trait CollectSlice<'a>: Iterator { + fn inner_array(&mut self) -> [Self::Item; N]; + + fn collect_array(&mut self) -> [Self::Item; N] { + let result = self.inner_array(); + assert!(self.next().is_none()); + result + } +} + +impl<'a, I: ?Sized> CollectSlice<'a> for I +where + I: Iterator, +{ + fn inner_array(&mut self) -> [Self::Item; N] { + let mut result: [MaybeUninit; N] = + unsafe { MaybeUninit::uninit().assume_init() }; + + let mut count = 0; + for (dest, item) in result.iter_mut().zip(self) { + *dest = MaybeUninit::new(item); + count += 1; + } + + assert_eq!(N, count); + + let temp_ptr: *const [MaybeUninit; N] = &result; + unsafe { std::ptr::read(temp_ptr as *const [Self::Item; N]) } + } +} + +fn main() { + let mut foos = [0u64; 9].iter().cloned(); + let _bar: [u64; 9] = foos.collect_array::<9_usize>(); +}