rustc_trans: Fix type projection debuginfo

Closes #20797

src/test/debuginfo/associated_types.rs

@@ -0,0 +1,28 @@
+// Copyright 2013-2014 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.
+
+// ignore-android: FIXME(#10381)
+// min-lldb-version: 310
+
+// compile-flags:-g
+
+struct Peekable<I> where I: Iterator {
+    _iter: I,
+    _next: Option<<I as Iterator>::Item>,
+}
+
+fn main() {
+    let mut iter = Vec::<i32>::new().into_iter();
+    let next = iter.next();
+    let _v = Peekable {
+        _iter: iter,
+        _next : next,
+    };
+}