From 5b5b4bbbea7217969509dd3a20318744ecf247cd Mon Sep 17 00:00:00 2001
From: Nick Mathewson <nickm@torproject.org>
Date: Thu, 19 May 2022 08:09:05 -0400
Subject: [PATCH] Simplify advance and reset functions with mem::replace.

---
 crates/tor-dirmgr/src/bootstrap.rs | 12 ++++--------
 1 file changed, 4 insertions(+), 8 deletions(-)

diff --git a/crates/tor-dirmgr/src/bootstrap.rs b/crates/tor-dirmgr/src/bootstrap.rs
index 009fb9d50..4d120f40a 100644
--- a/crates/tor-dirmgr/src/bootstrap.rs
+++ b/crates/tor-dirmgr/src/bootstrap.rs
@@ -594,18 +594,14 @@ pub(crate) async fn download<R: Runtime>(
 
 /// Replace `state` with `state.reset()`.
 fn reset(state: &mut Box<dyn DirState>) {
-    let mut this_state: Box<dyn DirState> = Box::new(PoisonedState);
-    std::mem::swap(&mut this_state, state);
-    this_state = this_state.reset();
-    std::mem::swap(&mut this_state, state);
+    let cur_state = std::mem::replace(state, Box::new(PoisonedState));
+    *state = cur_state.reset();
 }
 
 /// Replace `state` with `state.advance()`.
 fn advance(state: &mut Box<dyn DirState>) {
-    let mut this_state: Box<dyn DirState> = Box::new(PoisonedState);
-    std::mem::swap(&mut this_state, state);
-    this_state = this_state.advance();
-    std::mem::swap(&mut this_state, state);
+    let cur_state = std::mem::replace(state, Box::new(PoisonedState));
+    *state = cur_state.advance();
 }
 
 /// Helper: Clamp `v` so that it is no more than one week from `now`.