Switched to Box::new in many places.

Many of the modifications putting in `Box::new` calls also include a
pointer to Issue 22405, which tracks going back to `box <expr>` if
possible in the future.

(Still tried to use `Box<_>` where it sufficed; thus some tests still
have `box_syntax` enabled, as they use a mix of `box` and `Box::new`.)

Precursor for overloaded-`box` and placement-`in`; see Issue 22181.

2 files changed, 7 insertions, 4 deletions

diff --git a/src/libstd/old_io/stdio.rs b/src/libstd/old_io/stdio.rs
index a5df21749e2..85bf4908f83 100644
--- a/src/libstd/old_io/stdio.rs
+++ b/src/libstd/old_io/stdio.rs
@@ -547,8 +547,9 @@ mod tests {
 
         let (tx, rx) = channel();
         let (mut r, w) = (ChanReader::new(rx), ChanWriter::new(tx));
+        // FIXME (#22405): Replace `Box::new` with `box` here when/if possible.
         let _t = thread::spawn(move|| {
-            set_stdout(box w);
+            set_stdout(Box::new(w));
             println!("hello!");
         });
         assert_eq!(r.read_to_string().unwrap(), "hello!\n");
@@ -560,8 +561,9 @@ mod tests {
 
         let (tx, rx) = channel();
         let (mut r, w) = (ChanReader::new(rx), ChanWriter::new(tx));
+        // FIXME (#22405): Replace `Box::new` with `box` here when/if possible.
         let _t = thread::spawn(move || -> () {
-            set_stderr(box w);
+            set_stderr(Box::new(w));
             panic!("my special message");
         });
         let s = r.read_to_string().unwrap();
diff --git a/src/libstd/old_io/timer.rs b/src/libstd/old_io/timer.rs
index 1f2ef50fcae..de5f2141095 100644
--- a/src/libstd/old_io/timer.rs
+++ b/src/libstd/old_io/timer.rs
@@ -15,6 +15,7 @@
 
 // FIXME: These functions take Durations but only pass ms to the backend impls.
 
+use boxed::Box;
 use sync::mpsc::{Receiver, Sender, channel};
 use time::Duration;
 use old_io::IoResult;
@@ -143,7 +144,7 @@ impl Timer {
         let (tx, rx) = channel();
         // Short-circuit the timer backend for 0 duration
         if in_ms_u64(duration) != 0 {
-            self.inner.oneshot(in_ms_u64(duration), box TimerCallback { tx: tx });
+            self.inner.oneshot(in_ms_u64(duration), Box::new(TimerCallback { tx: tx }));
         } else {
             tx.send(()).unwrap();
         }
@@ -204,7 +205,7 @@ impl Timer {
         // not clear what use a 0ms period is anyway...
         let ms = if ms == 0 { 1 } else { ms };
         let (tx, rx) = channel();
-        self.inner.period(ms, box TimerCallback { tx: tx });
+        self.inner.period(ms, Box::new(TimerCallback { tx: tx }));
         return rx
     }
 }