Add regression tests for #23595

Closes #23595

Author: frewsxcv

src/test/compile-fail/issue-23595-1.rs

@@ -0,0 +1,22 @@
+// 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};
+
+trait Hierarchy {
+    type Value;
+    type ChildKey;
+    type Children = Index<Self::ChildKey, Output=Hierarchy>;
+    //~^ ERROR: the value of the associated type must be specified
+
+    fn data(&self) -> Option<(Self::Value, Self::Children)>;
+}
+
+fn main() {}

src/test/compile-fail/issue-23595-2.rs

@@ -0,0 +1,18 @@
+// 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.
+
+pub struct C<AType: A> {a:AType}
+
+pub trait A {
+    type B = C<Self::anything_here_kills_it>;
+    //~^ ERROR: associated type `anything_here_kills_it` not found for `Self`
+}
+
+fn main() {}