From 736c3d7bb79fb0b29c479e3191e5cad27f9872fb Mon Sep 17 00:00:00 2001
From: Eh2406 <YeomanYaacov@gmail.com>
Date: Thu, 5 Apr 2018 16:34:49 -0400
Subject: [PATCH 1/2] use more Rc in the part of resolver that gets cloned a
 lot

---
 src/cargo/core/resolver/context.rs | 13 ++++++++-----
 1 file changed, 8 insertions(+), 5 deletions(-)

diff --git a/src/cargo/core/resolver/context.rs b/src/cargo/core/resolver/context.rs
index b2b49a6b5a2..f132463e3c8 100644
--- a/src/cargo/core/resolver/context.rs
+++ b/src/cargo/core/resolver/context.rs
@@ -23,7 +23,7 @@ pub struct Context {
     //       switch to persistent hash maps if we can at some point or otherwise
     //       make these much cheaper to clone in general.
     pub activations: Activations,
-    pub resolve_features: HashMap<PackageId, HashSet<InternedString>>,
+    pub resolve_features: HashMap<PackageId, Rc<HashSet<InternedString>>>,
     pub links: HashMap<InternedString, PackageId>,
 
     // These are two cheaply-cloneable lists (O(1) clone) which are effectively
@@ -36,6 +36,8 @@ pub struct Context {
     pub warnings: RcList<String>,
 }
 
+pub type Activations = HashMap<(InternedString, SourceId), Rc<Vec<Summary>>>;
+
 impl Context {
     pub fn new() -> Context {
         Context {
@@ -246,10 +248,13 @@ impl Context {
 
             let set = self.resolve_features
                 .entry(pkgid.clone())
-                .or_insert_with(HashSet::new);
+                .or_insert_with(|| Rc::new(HashSet::new()));
+
+            let mut inner: HashSet<_> = (**set).clone();
             for feature in reqs.used {
-                set.insert(InternedString::new(feature));
+                inner.insert(InternedString::new(feature));
             }
+            *set = Rc::new(inner);
         }
 
         Ok(ret)
@@ -405,5 +410,3 @@ impl<'r> Requirements<'r> {
         }
     }
 }
-
-pub type Activations = HashMap<(InternedString, SourceId), Rc<Vec<Summary>>>;

From 04fbc5f6e8d4b2ff5de1fb3d58dbccda9fcc8aff Mon Sep 17 00:00:00 2001
From: Eh2406 <YeomanYaacov@gmail.com>
Date: Fri, 6 Apr 2018 12:38:41 -0400
Subject: [PATCH 2/2] use make_mut for cleaner code

---
 src/cargo/core/resolver/context.rs | 12 ++++--------
 1 file changed, 4 insertions(+), 8 deletions(-)

diff --git a/src/cargo/core/resolver/context.rs b/src/cargo/core/resolver/context.rs
index f132463e3c8..2c2281d6107 100644
--- a/src/cargo/core/resolver/context.rs
+++ b/src/cargo/core/resolver/context.rs
@@ -68,9 +68,7 @@ impl Context {
                     &*link
                 );
             }
-            let mut inner: Vec<_> = (**prev).clone();
-            inner.push(summary.clone());
-            *prev = Rc::new(inner);
+            Rc::make_mut(prev).push(summary.clone());
             return Ok(false);
         }
         debug!("checking if {} is already activated", summary.package_id());
@@ -246,15 +244,13 @@ impl Context {
         if !reqs.used.is_empty() {
             let pkgid = s.package_id();
 
-            let set = self.resolve_features
+            let set = Rc::make_mut(self.resolve_features
                 .entry(pkgid.clone())
-                .or_insert_with(|| Rc::new(HashSet::new()));
+                .or_insert_with(|| Rc::new(HashSet::new())));
 
-            let mut inner: HashSet<_> = (**set).clone();
             for feature in reqs.used {
-                inner.insert(InternedString::new(feature));
+                set.insert(InternedString::new(feature));
             }
-            *set = Rc::new(inner);
         }
 
         Ok(ret)