Add regression test for #22312

Closes #22312

Author: frewsxcv

src/test/compile-fail/issue-22312.rs

@@ -0,0 +1,27 @@
+// Copyright 2015 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+use std::ops::Index;
+
+pub trait Array2D: Index<usize> {
+    fn rows(&self) -> usize;
+    fn columns(&self) -> usize;
+    fn get<'a>(&'a self, y: usize, x: usize) -> Option<&'a <Self as Index<usize>>::Output> {
+        if y >= self.rows() || x >= self.columns() {
+            return None;
+        }
+        let i = y * self.columns() + x;
+        let indexer = &(*self as &Index<usize, Output = <Self as Index<usize>>::Output>);
+        //~^ERROR non-scalar cast
+        Some(indexer.index(i))
+    }
+}
+
+fn main() {}