move some parts of liveness to happen during type checking

This allows us to re-use the `normalize` method on `TypeCheck`, which
is important since normalization may create fresh region
variables. This is not an ideal solution, though, since the current
representation of "liveness constraints" (a vector of (region, point)
pairs) is rather inefficient. Could do somewhat better by converting
to indices, but it'd still be less good than the older code. Unclear
how important this is.

src/test/ui/nll/ty-outlives/projection-fn.rs

@@ -0,0 +1,53 @@
+// 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
+
+#![allow(warnings)]
+#![feature(dyn_trait)]
+
+trait Anything { }
+
+impl<T> Anything for T { }
+
+fn no_region<'a, T>(mut x: T) -> Box<dyn Anything + 'a>
+where
+    T: Iterator,
+{
+    Box::new(x.next())
+    //~^ WARNING not reporting region error due to -Znll
+    //~| ERROR failed type test
+}
+
+fn correct_region<'a, T>(mut x: T) -> Box<dyn Anything + 'a>
+where
+    T: 'a + Iterator,
+{
+    Box::new(x.next())
+}
+
+fn wrong_region<'a, 'b, T>(mut x: T) -> Box<dyn Anything + 'a>
+where
+    T: 'b + Iterator,
+{
+    Box::new(x.next())
+    //~^ WARNING not reporting region error due to -Znll
+    //~| ERROR failed type test
+}
+
+fn outlives_region<'a, 'b, T>(mut x: T) -> Box<dyn Anything + 'a>
+where
+    T: 'b + Iterator,
+    'b: 'a,
+{
+    Box::new(x.next())
+}
+
+fn main() {}

src/test/ui/nll/ty-outlives/projection-fn.stderr

@@ -0,0 +1,26 @@
+warning: not reporting region error due to -Znll
+  --> $DIR/projection-fn.rs:24:5
+   |
+24 |     Box::new(x.next())
+   |     ^^^^^^^^^^^^^^^^^^
+
+warning: not reporting region error due to -Znll
+  --> $DIR/projection-fn.rs:40:5
+   |
+40 |     Box::new(x.next())
+   |     ^^^^^^^^^^^^^^^^^^
+
+error: failed type test: TypeTest { generic_kind: ProjectionTy { substs: Slice([T]), item_def_id: DefId(2/0:1695 ~ core[2633]::iter[0]::iterator[0]::Iterator[0]::Item[0]) }, lower_bound: '_#3r, point: bb5[0], span: $DIR/projection-fn.rs:24:5: 24:23, test: IsOutlivedByAnyRegionIn([]) }
+  --> $DIR/projection-fn.rs:24:5
+   |
+24 |     Box::new(x.next())
+   |     ^^^^^^^^^^^^^^^^^^
+
+error: failed type test: TypeTest { generic_kind: ProjectionTy { substs: Slice([T]), item_def_id: DefId(2/0:1695 ~ core[2633]::iter[0]::iterator[0]::Iterator[0]::Item[0]) }, lower_bound: '_#4r, point: bb5[0], span: $DIR/projection-fn.rs:40:5: 40:23, test: IsOutlivedByAnyRegionIn(['_#2r]) }
+  --> $DIR/projection-fn.rs:40:5
+   |
+40 |     Box::new(x.next())
+   |     ^^^^^^^^^^^^^^^^^^
+
+error: aborting due to 2 previous errors
+