Add new tests, fix up old tests

src/test/ui/autoref-autoderef/deref-into-array.rs

@@ -0,0 +1,17 @@
+// check-pass
+
+struct Test<T>([T; 1]);
+
+impl<T> std::ops::Deref for Test<T> {
+    type Target = [T; 1];
+
+    fn deref(&self) -> &[T; 1] {
+        &self.0
+    }
+}
+
+fn main() {
+    let out = Test([(); 1]);
+    let blah = out.len();
+    println!("{}", blah);
+}

src/test/ui/const-generics/deref-into-array-generic.rs

@@ -0,0 +1,27 @@
+// check-pass
+
+struct Test<T, const N: usize>([T; N]);
+
+impl<T: Copy + Default, const N: usize> Default for Test<T, N> {
+    fn default() -> Self {
+        Self([T::default(); N])
+    }
+}
+
+impl<T, const N: usize> std::ops::Deref for Test<T, N> {
+    type Target = [T; N];
+
+    fn deref(&self) -> &[T; N] {
+        &self.0
+    }
+}
+
+fn test() -> Test<u64, 16> {
+    let test = Test::default();
+    println!("{}", test.len());
+    test
+}
+
+fn main() {
+    test();
+}