Normalize associated types in bounds too. Also, make the workaround

for lack of impl-trait-for-trait just a bit more targeted (don't
substitute err, just drop the troublesome bound for now) -- otherwise
substituting false types leads us into trouble when we normalize etc.

src/test/run-pass/associated-types-normalize-in-bounds.rs

@@ -0,0 +1,41 @@
+// 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.
+
+// Test that we normalize associated types that appear in bounds; if
+// we didn't, the call to `self.split2()` fails to type check.
+
+#![feature(associated_types)]
+
+struct Splits<'a, T, P>;
+struct SplitsN<I>;
+
+trait SliceExt2 for Sized? {
+    type Item;
+
+    fn split2<'a, P>(&'a self, pred: P) -> Splits<'a, Self::Item, P>
+        where P: FnMut(&Self::Item) -> bool;
+    fn splitn2<'a, P>(&'a self, n: uint, pred: P) -> SplitsN<Splits<'a, Self::Item, P>>
+        where P: FnMut(&Self::Item) -> bool;
+}
+
+impl<T> SliceExt2 for [T] {
+    type Item = T;
+
+    fn split2<P>(&self, pred: P) -> Splits<T, P> where P: FnMut(&T) -> bool {
+        loop {}
+    }
+
+    fn splitn2<P>(&self, n: uint, pred: P) -> SplitsN<Splits<T, P>> where P: FnMut(&T) -> bool {
+        self.split2(pred);
+        loop {}
+    }
+}
+
+fn main() { }