librustc: Make sure region bounds on closures outlive calls to them.

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]

1 files changed, 16 insertions, 0 deletions

diff --git a/src/test/compile-fail/region-bound-on-closure-outlives-call.rs b/src/test/compile-fail/region-bound-on-closure-outlives-call.rs
new file mode 100644
index 00000000000..13ab7acaf48
--- /dev/null
+++ b/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() {}
+