add regression test for rust-lang#70586

Author: lcnr

src/test/ui/const-generics/type-dependent/issue-70586.rs

@@ -0,0 +1,33 @@
+// check-pass
+#![feature(const_generics)]
+#![allow(incomplete_features)]
+
+use std::marker::PhantomData;
+
+// This namespace is necessary for the ICE to trigger
+struct Namespace;
+
+impl Namespace {
+    pub fn const_chunks_exact<T, const N: usize>() -> ConstChunksExact<'static, T, N> {
+        ConstChunksExact { inner: PhantomData }
+    }
+}
+
+
+#[derive(Debug)]
+pub struct ConstChunksExact<'a, T, const N: usize> {
+    inner:  PhantomData<&'a T>
+}
+
+impl <'a, T, const N: usize> Iterator for ConstChunksExact<'a, T, { N }> {
+    type Item = &'a [T; N];
+
+    fn next(&mut self) -> Option<Self::Item> {
+        unreachable!()
+    }
+}
+
+fn main() {
+    let mut chunks = Namespace::const_chunks_exact::<i32, 3usize>();
+    let _next: &[i32; 3] = chunks.next().unwrap();
+}