From ae532730215f1e74b175d1aa214146e9d900e5fd Mon Sep 17 00:00:00 2001
From: ljedrz <ljedrz@gmail.com>
Date: Mon, 3 Dec 2018 16:22:27 +0100
Subject: [PATCH] slice: tweak concat & join

---
 src/liballoc/slice.rs | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/src/liballoc/slice.rs b/src/liballoc/slice.rs
index 22da9dd6e9619..e012d56f48b48 100644
--- a/src/liballoc/slice.rs
+++ b/src/liballoc/slice.rs
@@ -589,7 +589,7 @@ impl<T: Clone, V: Borrow<[T]>> SliceConcatExt<T> for [V] {
     type Output = Vec<T>;
 
     fn concat(&self) -> Vec<T> {
-        let size = self.iter().fold(0, |acc, v| acc + v.borrow().len());
+        let size = self.iter().map(|slice| slice.borrow().len()).sum();
         let mut result = Vec::with_capacity(size);
         for v in self {
             result.extend_from_slice(v.borrow())
@@ -603,8 +603,8 @@ impl<T: Clone, V: Borrow<[T]>> SliceConcatExt<T> for [V] {
             Some(first) => first,
             None => return vec![],
         };
-        let size = self.iter().fold(0, |acc, v| acc + v.borrow().len());
-        let mut result = Vec::with_capacity(size + self.len());
+        let size = self.iter().map(|slice| slice.borrow().len()).sum::<usize>() + self.len() - 1;
+        let mut result = Vec::with_capacity(size);
         result.extend_from_slice(first.borrow());
 
         for v in iter {