Auto merge of #26904 - bluss:no-repeat, r=alexcrichton

In a followup to PR #26849, improve one more location for I/O where
we can use `Vec::resize` to ensure better performance when zeroing
buffers.

Use the `vec![elt; n]` macro everywhere we can in the tree. It replaces
`repeat(elt).take(n).collect()` which is more verbose, requires type
hints, and right now produces worse code. `vec![]` is preferable for vector
initialization.

The `vec![]` replacement touches upon one I/O path too, Stdin::read
for windows, and that should be a small improvement.

r? @alexcrichton 

1 files changed, 1 insertions, 2 deletions

diff --git a/src/libstd/sys/windows/stdio.rs b/src/libstd/sys/windows/stdio.rs
index 9961fef714a..356787d5bf0 100644
--- a/src/libstd/sys/windows/stdio.rs
+++ b/src/libstd/sys/windows/stdio.rs
@@ -12,7 +12,6 @@ use prelude::v1::*;
 use io::prelude::*;
 
 use io::{self, Cursor};
-use iter::repeat;
 use libc;
 use ptr;
 use str;
@@ -94,7 +93,7 @@ impl Stdin {
         let mut utf8 = self.utf8.lock().unwrap();
         // Read more if the buffer is empty
         if utf8.position() as usize == utf8.get_ref().len() {
-            let mut utf16: Vec<u16> = repeat(0u16).take(0x1000).collect();
+            let mut utf16 = vec![0u16; 0x1000];
             let mut num = 0;
             try!(cvt(unsafe {
                 c::ReadConsoleW(handle,