Auto merge of #25548 - sfackler:debug-builders-by-ref, r=alexcrichton

Based on feedback from https://internals.rust-lang.org/t/final-comment-period-for-debug-builders-stabilization/2007/2

4 files changed, 16 insertions, 15 deletions

diff --git a/src/libstd/collections/hash/map.rs b/src/libstd/collections/hash/map.rs
index a5fbc4374e0..093218c6e4c 100644
--- a/src/libstd/collections/hash/map.rs
+++ b/src/libstd/collections/hash/map.rs
@@ -1222,7 +1222,7 @@ impl<K, V, S> Debug for HashMap<K, V, S>
     where K: Eq + Hash + Debug, V: Debug, S: HashState
 {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
-        self.iter().fold(f.debug_map(), |b, (k, v)| b.entry(k, v)).finish()
+        f.debug_map().entries(self.iter()).finish()
     }
 }
 
diff --git a/src/libstd/collections/hash/set.rs b/src/libstd/collections/hash/set.rs
index d6754f10335..44fc0f7016d 100644
--- a/src/libstd/collections/hash/set.rs
+++ b/src/libstd/collections/hash/set.rs
@@ -585,7 +585,7 @@ impl<T, S> fmt::Debug for HashSet<T, S>
           S: HashState
 {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
-        self.iter().fold(f.debug_set(), |b, e| b.entry(e)).finish()
+        f.debug_set().entries(self.iter()).finish()
     }
 }
 
diff --git a/src/libstd/sys/common/net.rs b/src/libstd/sys/common/net.rs
index 7da7071670a..efbcda3fece 100644
--- a/src/libstd/sys/common/net.rs
+++ b/src/libstd/sys/common/net.rs
@@ -274,16 +274,16 @@ impl fmt::Debug for TcpStream {
         let mut res = f.debug_struct("TcpStream");
 
         if let Ok(addr) = self.socket_addr() {
-            res = res.field("addr", &addr);
+            res.field("addr", &addr);
         }
 
         if let Ok(peer) = self.peer_addr() {
-            res = res.field("peer", &peer);
+            res.field("peer", &peer);
         }
 
         let name = if cfg!(windows) {"socket"} else {"fd"};
-        res = res.field(name, &self.inner.as_inner());
-        res.finish()
+        res.field(name, &self.inner.as_inner())
+            .finish()
     }
 }
 
@@ -351,12 +351,12 @@ impl fmt::Debug for TcpListener {
         let mut res = f.debug_struct("TcpListener");
 
         if let Ok(addr) = self.socket_addr() {
-            res = res.field("addr", &addr);
+            res.field("addr", &addr);
         }
 
         let name = if cfg!(windows) {"socket"} else {"fd"};
-        res = res.field(name, &self.inner.as_inner());
-        res.finish()
+        res.field(name, &self.inner.as_inner())
+            .finish()
     }
 }
 
@@ -484,11 +484,11 @@ impl fmt::Debug for UdpSocket {
         let mut res = f.debug_struct("UdpSocket");
 
         if let Ok(addr) = self.socket_addr() {
-            res = res.field("addr", &addr);
+            res.field("addr", &addr);
         }
 
         let name = if cfg!(windows) {"socket"} else {"fd"};
-        res = res.field(name, &self.inner.as_inner());
-        res.finish()
+        res.field(name, &self.inner.as_inner())
+            .finish()
     }
 }
diff --git a/src/libstd/sys/unix/fs.rs b/src/libstd/sys/unix/fs.rs
index 350161c751c..51a85a276ed 100644
--- a/src/libstd/sys/unix/fs.rs
+++ b/src/libstd/sys/unix/fs.rs
@@ -408,12 +408,13 @@ impl fmt::Debug for File {
         }
 
         let fd = self.0.raw();
-        let mut b = f.debug_struct("File").field("fd", &fd);
+        let mut b = f.debug_struct("File");
+        b.field("fd", &fd);
         if let Some(path) = get_path(fd) {
-            b = b.field("path", &path);
+            b.field("path", &path);
         }
         if let Some((read, write)) = get_mode(fd) {
-            b = b.field("read", &read).field("write", &write);
+            b.field("read", &read).field("write", &write);
         }
         b.finish()
     }