Fix DeBruijn accounting. It used to be that all trait-refs were binders,

but now only poly-trait-refs are binders. Fixes #20831.

src/test/compile-fail/issue-20831-debruijn.rs

@@ -0,0 +1,49 @@
+// 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.
+
+// Regression test for #20831: debruijn index account was thrown off
+// by the (anonymous) lifetime in `<Self as Publisher>::Output`
+// below. Note that changing to a named lifetime made the problem go
+// away.
+
+use std::ops::{Shl, Shr};
+use std::cell::RefCell;
+
+pub trait Subscriber {
+    type Input;
+}
+
+pub trait Publisher<'a> {
+    type Output;
+    fn subscribe(&mut self, Box<Subscriber<Input=Self::Output> + 'a>);
+}
+
+pub trait Processor<'a> : Subscriber + Publisher<'a> { }
+
+impl<'a, P> Processor<'a> for P where P : Subscriber + Publisher<'a> { }
+
+struct MyStruct<'a> {
+    sub: Box<Subscriber<Input=u64> + 'a>
+}
+
+impl<'a> Publisher<'a> for MyStruct<'a> {
+    type Output = u64;
+    fn subscribe(&mut self, t : Box<Subscriber<Input=<Self as Publisher>::Output> + 'a>) {
+        // Not obvious, but there is an implicit lifetime here -------^
+        //~^^ ERROR cannot infer
+        //
+        // The fact that `Publisher` is using an implicit lifetime is
+        // what was causing the debruijn accounting to be off, so
+        // leave it that way!
+        self.sub = t;
+    }
+}
+
+fn main() {}

src/test/run-pass/regions-debruijn-of-object.rs

@@ -0,0 +1,25 @@
+// 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.
+
+struct ctxt<'tcx> {
+    x: &'tcx i32
+}
+
+trait AstConv<'tcx> {
+    fn tcx<'a>(&'a self) -> &'a ctxt<'tcx>;
+}
+
+fn foo(conv: &AstConv) { }
+
+fn bar<'tcx>(conv: &AstConv<'tcx>) {
+    foo(conv)
+}
+
+fn main() { }