connect NLL type checker to the impl trait code

We now add the suitable `impl Trait` constraints.

src/test/ui/nll/ty-outlives/impl-trait-captures.rs

@@ -0,0 +1,27 @@
+// Copyright 2016 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.
+
+// compile-flags:-Znll -Zborrowck=mir -Zverbose
+
+#![allow(warnings)]
+#![feature(conservative_impl_trait)]
+
+trait Foo<'a> {
+}
+
+impl<'a, T> Foo<'a> for T { }
+
+fn foo<'a, T>(x: &T) -> impl Foo<'a> {
+    x
+        //~^ WARNING not reporting region error due to -Znll
+        //~| ERROR free region `'_#2r` does not outlive free region `ReEarlyBound(0, 'a)`
+}
+
+fn main() {}

src/test/ui/nll/ty-outlives/impl-trait-captures.stderr

@@ -0,0 +1,14 @@
+warning: not reporting region error due to -Znll
+  --> $DIR/impl-trait-captures.rs:22:5
+   |
+22 |     x
+   |     ^
+
+error: free region `'_#2r` does not outlive free region `ReEarlyBound(0, 'a)`
+  --> $DIR/impl-trait-captures.rs:22:5
+   |
+22 |     x
+   |     ^
+
+error: aborting due to previous error
+

src/test/ui/nll/ty-outlives/impl-trait-outlives.rs

@@ -0,0 +1,51 @@
+// Copyright 2016 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.
+
+// compile-flags:-Znll -Zborrowck=mir -Zverbose
+
+#![allow(warnings)]
+#![feature(conservative_impl_trait)]
+
+use std::fmt::Debug;
+
+fn no_region<'a, T>(x: Box<T>) -> impl Debug + 'a
+    //~^ WARNING not reporting region error due to -Znll
+where
+    T: Debug,
+{
+    x
+    //~^ ERROR `T` does not outlive
+}
+
+fn correct_region<'a, T>(x: Box<T>) -> impl Debug + 'a
+where
+    T: 'a + Debug,
+{
+    x
+}
+
+fn wrong_region<'a, 'b, T>(x: Box<T>) -> impl Debug + 'a
+    //~^ WARNING not reporting region error due to -Znll
+where
+    T: 'b + Debug,
+{
+    x
+    //~^ ERROR `T` does not outlive
+}
+
+fn outlives_region<'a, 'b, T>(x: Box<T>) -> impl Debug + 'a
+where
+    T: 'b + Debug,
+    'b: 'a,
+{
+    x
+}
+
+fn main() {}

src/test/ui/nll/ty-outlives/impl-trait-outlives.stderr

@@ -0,0 +1,26 @@
+warning: not reporting region error due to -Znll
+  --> $DIR/impl-trait-outlives.rs:18:35
+   |
+18 | fn no_region<'a, T>(x: Box<T>) -> impl Debug + 'a
+   |                                   ^^^^^^^^^^^^^^^
+
+warning: not reporting region error due to -Znll
+  --> $DIR/impl-trait-outlives.rs:34:42
+   |
+34 | fn wrong_region<'a, 'b, T>(x: Box<T>) -> impl Debug + 'a
+   |                                          ^^^^^^^^^^^^^^^
+
+error: `T` does not outlive `'_#1r`
+  --> $DIR/impl-trait-outlives.rs:23:5
+   |
+23 |     x
+   |     ^
+
+error: `T` does not outlive `'_#1r`
+  --> $DIR/impl-trait-outlives.rs:39:5
+   |
+39 |     x
+   |     ^
+
+error: aborting due to 2 previous errors
+