address review comments

src/test/run-pass/generator/yield-in-args-rev.rs

@@ -8,6 +8,10 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
+// Test that a borrow that occurs after a yield in the same
+// argument list is not treated as live across the yield by
+// type-checking.
+
 #![feature(generators)]
 
 fn foo(_a: (), _b: &bool) {}

src/test/run-pass/generator/yield-in-box.rs

@@ -0,0 +1,26 @@
+// Copyright 2017 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 box-statements with yields in them work.
+
+#![feature(generators, box_syntax)]
+
+fn main() {
+    let x = 0i32;
+    || {
+        let y = 2u32;
+        {
+            let _t = box (&x, yield 0, &y);
+        }
+        match box (&x, yield 0, &y) {
+            _t => {}
+        }
+    };
+}