From 7843af05a2bc178025bbfdee6ab7f9d37f85efe2 Mon Sep 17 00:00:00 2001
From: Xavientois <joshua.rampersad@hotmail.com>
Date: Fri, 15 Jan 2021 09:53:42 -0500
Subject: [PATCH 1/6] Add size hint for byte iterator over file

---
 library/std/src/io/mod.rs | 15 +++++++++++++++
 1 file changed, 15 insertions(+)

diff --git a/library/std/src/io/mod.rs b/library/std/src/io/mod.rs
index 3f5b7c0b29be6..ceb2d59c31b9c 100644
--- a/library/std/src/io/mod.rs
+++ b/library/std/src/io/mod.rs
@@ -253,6 +253,7 @@ mod tests;
 
 use crate::cmp;
 use crate::fmt;
+use crate::fs;
 use crate::memchr;
 use crate::ops::{Deref, DerefMut};
 use crate::ptr;
@@ -2464,6 +2465,20 @@ impl<R: Read> Iterator for Bytes<R> {
     }
 }
 
+impl Iterator for Bytes<fs::File> {
+    type Item = Result<u8>;
+
+    fn size_hint(&self) -> (usize, Option<usize>) {
+        match self.inner.metadata() {
+            Ok(metadata) => {
+                let file_length = metadata.len() as usize;
+                (file_length, Some(file_length))
+            }
+            Err(_) => (0, None),
+        }
+    }
+}
+
 /// An iterator over the contents of an instance of `BufRead` split on a
 /// particular byte.
 ///

From 0b5090a53463802144f32106a9d5cc0cf09b4676 Mon Sep 17 00:00:00 2001
From: Xavientois <joshua.rampersad@hotmail.com>
Date: Fri, 15 Jan 2021 10:24:32 -0500
Subject: [PATCH 2/6] Remove lower bound and fix compiler error from
 specialization

---
 library/std/src/io/mod.rs | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/library/std/src/io/mod.rs b/library/std/src/io/mod.rs
index ceb2d59c31b9c..a6fb4390eb246 100644
--- a/library/std/src/io/mod.rs
+++ b/library/std/src/io/mod.rs
@@ -2466,13 +2466,11 @@ impl<R: Read> Iterator for Bytes<R> {
 }
 
 impl Iterator for Bytes<fs::File> {
-    type Item = Result<u8>;
-
     fn size_hint(&self) -> (usize, Option<usize>) {
         match self.inner.metadata() {
             Ok(metadata) => {
                 let file_length = metadata.len() as usize;
-                (file_length, Some(file_length))
+                (0, Some(file_length))
             }
             Err(_) => (0, None),
         }

From f4e240edafbe50f15773c387f96e7da0fb3edd4f Mon Sep 17 00:00:00 2001
From: Xavientois <joshua.rampersad@hotmail.com>
Date: Fri, 15 Jan 2021 10:31:52 -0500
Subject: [PATCH 3/6] Specify default implementation for parent in order to
 allow specialization for File

---
 library/std/src/io/mod.rs | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/library/std/src/io/mod.rs b/library/std/src/io/mod.rs
index a6fb4390eb246..666b07db78a4f 100644
--- a/library/std/src/io/mod.rs
+++ b/library/std/src/io/mod.rs
@@ -2463,6 +2463,8 @@ impl<R: Read> Iterator for Bytes<R> {
             };
         }
     }
+
+    default fn size_hint(&self) -> (usize, Option<usize>) {}
 }
 
 impl Iterator for Bytes<fs::File> {

From ca124d1c2b0d6011fd3e346ac9a829fb5e5a854b Mon Sep 17 00:00:00 2001
From: Xavientois <joshua.rampersad@hotmail.com>
Date: Fri, 15 Jan 2021 10:39:59 -0500
Subject: [PATCH 4/6] Include default implementation for size_hint

---
 library/std/src/io/mod.rs | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/library/std/src/io/mod.rs b/library/std/src/io/mod.rs
index 666b07db78a4f..29ff0fd8b49da 100644
--- a/library/std/src/io/mod.rs
+++ b/library/std/src/io/mod.rs
@@ -2464,7 +2464,9 @@ impl<R: Read> Iterator for Bytes<R> {
         }
     }
 
-    default fn size_hint(&self) -> (usize, Option<usize>) {}
+    default fn size_hint(&self) -> (usize, Option<usize>) {
+        (0, None)
+    }
 }
 
 impl Iterator for Bytes<fs::File> {

From d90ac4fd8153892acf7b0c656e2c7d39b4616d0f Mon Sep 17 00:00:00 2001
From: Xavientois <joshua.rampersad@hotmail.com>
Date: Fri, 15 Jan 2021 10:54:51 -0500
Subject: [PATCH 5/6] Add stability attribute

---
 library/std/src/io/mod.rs | 1 +
 1 file changed, 1 insertion(+)

diff --git a/library/std/src/io/mod.rs b/library/std/src/io/mod.rs
index 29ff0fd8b49da..b65b53679a38b 100644
--- a/library/std/src/io/mod.rs
+++ b/library/std/src/io/mod.rs
@@ -2469,6 +2469,7 @@ impl<R: Read> Iterator for Bytes<R> {
     }
 }
 
+#[unstable(feature = "file_size_hint", reason = "New implementation optimization")]
 impl Iterator for Bytes<fs::File> {
     fn size_hint(&self) -> (usize, Option<usize>) {
         match self.inner.metadata() {

From d69b3acca4e49ddce058fd177a380bfc0a9f2af8 Mon Sep 17 00:00:00 2001
From: Xavientois <joshua.rampersad@hotmail.com>
Date: Fri, 15 Jan 2021 11:02:01 -0500
Subject: [PATCH 6/6] Remove annotations for unstable attribute

---
 library/std/src/io/mod.rs | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/library/std/src/io/mod.rs b/library/std/src/io/mod.rs
index b65b53679a38b..20cffc09fd2a8 100644
--- a/library/std/src/io/mod.rs
+++ b/library/std/src/io/mod.rs
@@ -2469,7 +2469,7 @@ impl<R: Read> Iterator for Bytes<R> {
     }
 }
 
-#[unstable(feature = "file_size_hint", reason = "New implementation optimization")]
+#[unstable]
 impl Iterator for Bytes<fs::File> {
     fn size_hint(&self) -> (usize, Option<usize>) {
         match self.inner.metadata() {