use mem::take where possible (#1507)

actix-http/src/body.rs

@@ -189,7 +189,7 @@ impl MessageBody for Body {
                 if len == 0 {
                     Poll::Ready(None)
                 } else {
-                    Poll::Ready(Some(Ok(mem::replace(bin, Bytes::new()))))
+                    Poll::Ready(Some(Ok(mem::take(bin))))
                 }
             }
             Body::Message(ref mut body) => Pin::new(body.as_mut()).poll_next(cx),
@@ -307,7 +307,7 @@ impl MessageBody for Bytes {
         if self.is_empty() {
             Poll::Ready(None)
         } else {
-            Poll::Ready(Some(Ok(mem::replace(self.get_mut(), Bytes::new()))))
+            Poll::Ready(Some(Ok(mem::take(self.get_mut()))))
         }
     }
 }
@@ -324,9 +324,7 @@ impl MessageBody for BytesMut {
         if self.is_empty() {
             Poll::Ready(None)
         } else {
-            Poll::Ready(Some(Ok(
+            Poll::Ready(Some(Ok(mem::take(self.get_mut()).freeze())))
-                mem::replace(self.get_mut(), BytesMut::new()).freeze()
-            )))
         }
     }
 }
@@ -344,7 +342,7 @@ impl MessageBody for &'static str {
             Poll::Ready(None)
         } else {
             Poll::Ready(Some(Ok(Bytes::from_static(
-                mem::replace(self.get_mut(), "").as_ref(),
+                mem::take(self.get_mut()).as_ref(),
             ))))
         }
     }
@@ -362,10 +360,7 @@ impl MessageBody for Vec<u8> {
         if self.is_empty() {
             Poll::Ready(None)
         } else {
-            Poll::Ready(Some(Ok(Bytes::from(mem::replace(
+            Poll::Ready(Some(Ok(Bytes::from(mem::take(self.get_mut())))))
-                self.get_mut(),
-                Vec::new(),
-            )))))
         }
     }
 }
@@ -383,7 +378,7 @@ impl MessageBody for String {
             Poll::Ready(None)
         } else {
             Poll::Ready(Some(Ok(Bytes::from(
-                mem::replace(self.get_mut(), String::new()).into_bytes(),
+                mem::take(self.get_mut()).into_bytes(),
             ))))
         }
     }

actix-http/src/cookie/jar.rs

@@ -1,5 +1,5 @@
 use std::collections::HashSet;
-use std::mem::replace;
+use std::mem;
 
 use time::{Duration, OffsetDateTime};
 
@@ -273,7 +273,7 @@ impl CookieJar {
     )]
     pub fn clear(&mut self) {
         self.delta_cookies.clear();
-        for delta in replace(&mut self.original_cookies, HashSet::new()) {
+        for delta in mem::take(&mut self.original_cookies) {
             self.remove(delta.cookie);
         }
     }

actix-http/src/encoding/encoder.rs

@@ -106,7 +106,7 @@ impl<B: MessageBody> MessageBody for EncoderBody<B> {
                 if b.is_empty() {
                     Poll::Ready(None)
                 } else {
-                    Poll::Ready(Some(Ok(std::mem::replace(b, Bytes::new()))))
+                    Poll::Ready(Some(Ok(std::mem::take(b))))
                 }
             }
             EncoderBody::Stream(b) => b.poll_next(cx),

actix-http/src/h1/dispatcher.rs

@@ -1,6 +1,3 @@
-// Because MSRV is 1.39.0.
-#![allow(clippy::mem_replace_with_default)]
-
 use std::collections::VecDeque;
 use std::future::Future;
 use std::pin::Pin;
@@ -795,13 +792,10 @@ where
                             let inner_p = inner.as_mut().project();
                             let mut parts = FramedParts::with_read_buf(
                                 inner_p.io.take().unwrap(),
-                                std::mem::replace(inner_p.codec, Codec::default()),
+                                std::mem::take(inner_p.codec),
-                                std::mem::replace(inner_p.read_buf, BytesMut::default()),
+                                std::mem::take(inner_p.read_buf),
-                            );
-                            parts.write_buf = std::mem::replace(
-                                inner_p.write_buf,
-                                BytesMut::default(),
                             );
+                            parts.write_buf = std::mem::take(inner_p.write_buf);
                             let framed = Framed::from_parts(parts);
                             let upgrade =
                                 inner_p.upgrade.take().unwrap().call((req, framed));

actix-session/src/lib.rs

@@ -200,8 +200,7 @@ impl Session {
             .extensions()
             .get::<Rc<RefCell<SessionInner>>>()
         {
-            let state =
+            let state = std::mem::take(&mut s_impl.borrow_mut().state);
-                std::mem::replace(&mut s_impl.borrow_mut().state, HashMap::new());
             (s_impl.borrow().status.clone(), Some(state.into_iter()))
         } else {
             (SessionStatus::Unchanged, None)

src/app_service.rs

@@ -12,7 +12,7 @@ use actix_service::{fn_service, Service, ServiceFactory};
 use futures::future::{join_all, ok, FutureExt, LocalBoxFuture};
 
 use crate::config::{AppConfig, AppService};
-use crate::data::{FnDataFactory, DataFactory};
+use crate::data::{DataFactory, FnDataFactory};
 use crate::error::Error;
 use crate::guard::Guard;
 use crate::request::{HttpRequest, HttpRequestPool};
@@ -76,7 +76,7 @@ where
         let mut config = AppService::new(config, default.clone(), self.data.clone());
 
         // register services
-        std::mem::replace(&mut *self.services.borrow_mut(), Vec::new())
+        std::mem::take(&mut *self.services.borrow_mut())
             .into_iter()
             .for_each(|mut srv| srv.register(&mut config));
 
@@ -99,7 +99,7 @@ where
         });
 
         // external resources
-        for mut rdef in std::mem::replace(&mut *self.external.borrow_mut(), Vec::new()) {
+        for mut rdef in std::mem::take(&mut *self.external.borrow_mut()) {
             rmap.add(&mut rdef, None);
         }
 

src/resource.rs

@@ -379,7 +379,7 @@ where
         let guards = if self.guards.is_empty() {
             None
         } else {
-            Some(std::mem::replace(&mut self.guards, Vec::new()))
+            Some(std::mem::take(&mut self.guards))
         };
         let mut rdef = if config.is_root() || !self.rdef.is_empty() {
             ResourceDef::new(insert_slash(self.rdef.clone()))

src/route.rs

@@ -56,7 +56,7 @@ impl Route {
     }
 
     pub(crate) fn take_guards(&mut self) -> Vec<Box<dyn Guard>> {
-        std::mem::replace(Rc::get_mut(&mut self.guards).unwrap(), Vec::new())
+        std::mem::take(Rc::get_mut(&mut self.guards).unwrap())
     }
 }
 

src/scope.rs

@@ -429,7 +429,7 @@ where
         let mut rmap = ResourceMap::new(ResourceDef::root_prefix(&self.rdef));
 
         // external resources
-        for mut rdef in std::mem::replace(&mut self.external, Vec::new()) {
+        for mut rdef in std::mem::take(&mut self.external) {
             rmap.add(&mut rdef, None);
         }
 

src/service.rs

@@ -515,7 +515,7 @@ where
         let guards = if self.guards.is_empty() {
             None
         } else {
-            Some(std::mem::replace(&mut self.guards, Vec::new()))
+            Some(std::mem::take(&mut self.guards))
         };
 
         let mut rdef = if config.is_root() || !self.rdef.is_empty() {