auto merge of #17175 : pcwalton/rust/region-bounds-on-closures, r=huonw

This can break code like:

    fn call_rec(f: |uint| -> uint) -> uint {
        (|x| f(x))(call_rec(f))
    }

Change this code to use a temporary instead of violating the borrow
rules:

    fn call_rec(f: |uint| -> uint) -> uint {
        let tmp = call_rec(|x| f(x)); f(tmp)
    }

Closes #17144.

[breaking-change]

r? @huonw

src/librustc/middle/typeck/check/regionck.rs

@@ -1064,6 +1064,10 @@ fn constrain_callee(rcx: &mut Rcx,
             };
             rcx.fcx.mk_subr(infer::InvokeClosure(callee_expr.span),
                             call_region, region);
+
+            let region = closure_ty.bounds.region_bound;
+            rcx.fcx.mk_subr(infer::InvokeClosure(callee_expr.span),
+                            call_region, region);
         }
         _ => {
             // this should not happen, but it does if the program is

src/test/compile-fail/region-bound-on-closure-outlives-call.rs

@@ -0,0 +1,16 @@
+// 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.
+
+fn call_rec(f: |uint| -> uint) -> uint {
+    (|x| f(x))(call_rec(f)) //~ ERROR cannot move out of `f`
+}
+
+fn main() {}
+