From 328abfb9431c486ab2d0b9ebd7f6115805f613de Mon Sep 17 00:00:00 2001
From: Giles Cope <gilescope@gmail.com>
Date: Tue, 26 Jan 2021 11:14:57 +0000
Subject: [PATCH 1/4] Slight simplification of chars().count()

---
 library/core/src/str/iter.rs | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/library/core/src/str/iter.rs b/library/core/src/str/iter.rs
index 8b952eab2946d..c37843434781a 100644
--- a/library/core/src/str/iter.rs
+++ b/library/core/src/str/iter.rs
@@ -47,12 +47,13 @@ impl<'a> Iterator for Chars<'a> {
     #[inline]
     fn count(self) -> usize {
         // length in `char` is equal to the number of non-continuation bytes
-        let bytes_len = self.iter.len();
-        let mut cont_bytes = 0;
+        let mut char_count = 0;
         for &byte in self.iter {
-            cont_bytes += utf8_is_cont_byte(byte) as usize;
+            if !utf8_is_cont_byte(byte) {
+                char_count += 1;
+            }
         }
-        bytes_len - cont_bytes
+        char_count
     }
 
     #[inline]

From 425a70a460abac1182a792c6c2af6dff69663c3c Mon Sep 17 00:00:00 2001
From: Giles Cope <gilescope@gmail.com>
Date: Tue, 26 Jan 2021 11:26:58 +0000
Subject: [PATCH 2/4] Removing if so it's more like the previous
 implementation.

---
 library/core/src/str/iter.rs | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/library/core/src/str/iter.rs b/library/core/src/str/iter.rs
index c37843434781a..34c31d599a318 100644
--- a/library/core/src/str/iter.rs
+++ b/library/core/src/str/iter.rs
@@ -49,9 +49,7 @@ impl<'a> Iterator for Chars<'a> {
         // length in `char` is equal to the number of non-continuation bytes
         let mut char_count = 0;
         for &byte in self.iter {
-            if !utf8_is_cont_byte(byte) {
-                char_count += 1;
-            }
+            char_count += !utf8_is_cont_byte(byte) as usize;
         }
         char_count
     }

From c07e5585b312aaa76f7bd35e60cf8e8d9164369c Mon Sep 17 00:00:00 2001
From: Giles Cope <gilescope@gmail.com>
Date: Tue, 26 Jan 2021 11:36:02 +0000
Subject: [PATCH 3/4] Let's try the most idiomatic way.

---
 library/core/src/str/iter.rs | 6 +-----
 1 file changed, 1 insertion(+), 5 deletions(-)

diff --git a/library/core/src/str/iter.rs b/library/core/src/str/iter.rs
index 34c31d599a318..0c74f6e45a784 100644
--- a/library/core/src/str/iter.rs
+++ b/library/core/src/str/iter.rs
@@ -47,11 +47,7 @@ impl<'a> Iterator for Chars<'a> {
     #[inline]
     fn count(self) -> usize {
         // length in `char` is equal to the number of non-continuation bytes
-        let mut char_count = 0;
-        for &byte in self.iter {
-            char_count += !utf8_is_cont_byte(byte) as usize;
-        }
-        char_count
+        self.iter.map(|&byte| !utf8_is_cont_byte(byte) as usize).sum()
     }
 
     #[inline]

From a623ea5301737507a8229c2ddae74b20f727bd1b Mon Sep 17 00:00:00 2001
From: Giles Cope <gilescope@gmail.com>
Date: Tue, 26 Jan 2021 21:51:18 +0000
Subject: [PATCH 4/4] Same instructions, but simpler.

---
 library/core/src/str/iter.rs | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/library/core/src/str/iter.rs b/library/core/src/str/iter.rs
index 0c74f6e45a784..83f484dc570c4 100644
--- a/library/core/src/str/iter.rs
+++ b/library/core/src/str/iter.rs
@@ -47,7 +47,7 @@ impl<'a> Iterator for Chars<'a> {
     #[inline]
     fn count(self) -> usize {
         // length in `char` is equal to the number of non-continuation bytes
-        self.iter.map(|&byte| !utf8_is_cont_byte(byte) as usize).sum()
+        self.iter.filter(|&&byte| !utf8_is_cont_byte(byte)).count()
     }
 
     #[inline]