Fix ICE that @steveklabnik encountered in rust-ice. The problems turned out to be that were being very loose with bound regions in trans (we were basically just ignoring and flattening binders). Since binders are significant to subtyping and hence to trait selection, this can cause a lot of problems. So this patch makes us treat them more strictly -- for example, we propagate binders, and avoid skipping past the Binder by writing foo.0.

Fixes #20644.

src/test/run-pass/issue-20644.rs

@@ -0,0 +1,35 @@
+// Copyright 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.
+
+// A reduced version of the rustbook ice. The problem this encountered
+// had to do with trans ignoring binders.
+
+#![feature(slicing_syntax)]
+#![feature(associated_types)]
+#![feature(macro_rules)]
+
+use std::iter;
+use std::os;
+use std::io::File;
+
+#[allow(unused)]
+pub fn parse_summary<R: Reader>(_: R, _: &Path) {
+     let path_from_root = Path::new("");
+     Path::new(iter::repeat("../")
+               .take(path_from_root.components().count() - 1)
+               .collect::<String>());
+ }
+
+fn main() {
+    let cwd = os::getcwd().unwrap();
+    let src = cwd.clone();
+    let summary = File::open(&src.join("SUMMARY.md"));
+    let _ = parse_summary(summary, &src);
+}