Add the notion of normalizing a parameter environment and ensure that

all parameter environments are normalized. Correspondingly, stop
normalizing predicates we extract out of the environment. Fixes #21664.

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

@@ -0,0 +1,42 @@
+// 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.
+
+// Test that we normalize associated types that appear in a bound that
+// contains a binding. Issue #21664.
+
+#![allow(dead_code)]
+
+pub trait Integral {
+    type Opposite;
+}
+
+impl Integral for i32 {
+    type Opposite = u32;
+}
+
+impl Integral for u32 {
+    type Opposite = i32;
+}
+
+pub trait FnLike<A> {
+    type R;
+}
+
+fn foo<T>()
+    where T : FnLike<<i32 as Integral>::Opposite, R=bool>
+{
+    bar::<T>();
+}
+
+fn bar<T>()
+    where T : FnLike<u32, R=bool>
+{}
+
+fn main() { }