diff --git a/Cargo.toml b/Cargo.toml
index ef5857b84..1a30c7064 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -68,7 +68,7 @@ walkdir = "2.2"
 clap = "2.31.2"
 unicode-width = "0.1.5"
 openssl = { version = '0.10.11', optional = true }
-im-rc = "14.0.0"
+im-rc = "15.0.0"
 
 # A noop dependency that changes in the Rust repository, it's a bit of a hack.
 # See the `src/tools/rustc-workspace-hack/README.md` file in `rust-lang/rust`
diff --git a/src/cargo/core/resolver/mod.rs b/src/cargo/core/resolver/mod.rs
index cde34a220..cb0e76025 100644
--- a/src/cargo/core/resolver/mod.rs
+++ b/src/cargo/core/resolver/mod.rs
@@ -844,7 +844,7 @@ fn generalize_conflicting(
     for (critical_parent, critical_parents_deps) in
         cx.parents.edges(&backtrack_critical_id).filter(|(p, _)| {
             // it will only help backjump further if it is older then the critical_age
-            cx.is_active(*p).expect("parent not currently active!?") < backtrack_critical_age
+            cx.is_active(**p).expect("parent not currently active!?") < backtrack_critical_age
         })
     {
         for critical_parents_dep in critical_parents_deps.iter() {
diff --git a/src/cargo/util/graph.rs b/src/cargo/util/graph.rs
index 8d2dc5b84..e5db1319e 100644
--- a/src/cargo/util/graph.rs
+++ b/src/cargo/util/graph.rs
@@ -37,7 +37,7 @@ impl<N: Eq + Ord + Clone, E: Default + Clone> Graph<N, E> {
         self.nodes.get(from)?.get(to)
     }
 
-    pub fn edges(&self, from: &N) -> impl Iterator<Item = &(N, E)> {
+    pub fn edges(&self, from: &N) -> impl Iterator<Item = (&N, &E)> {
         self.nodes.get(from).into_iter().flat_map(|x| x.iter())
     }
 
@@ -95,8 +95,8 @@ impl<N: Eq + Ord + Clone, E: Default + Clone> Graph<N, E> {
             p.iter()
                 // Note that we can have "cycles" introduced through dev-dependency
                 // edges, so make sure we don't loop infinitely.
-                .find(|&(node, _)| !result.contains(&node))
-                .map(|(ref p, _)| p)
+                .find(|(node, _)| !result.contains(node))
+                .map(|(p, _)| p)
         }) {
             result.push(p);
             pkg = p;
@@ -114,11 +114,11 @@ impl<N: Eq + Ord + Clone, E: Default + Clone> Graph<N, E> {
         let first_pkg_depending_on = |pkg: &N, res: &[&N]| {
             self.nodes
                 .iter()
-                .filter(|&(_, adjacent)| adjacent.contains_key(pkg))
+                .filter(|(_, adjacent)| adjacent.contains_key(pkg))
                 // Note that we can have "cycles" introduced through dev-dependency
                 // edges, so make sure we don't loop infinitely.
-                .find(|&(node, _)| !res.contains(&node))
-                .map(|(ref p, _)| p)
+                .find(|(node, _)| !res.contains(node))
+                .map(|(p, _)| p)
         };
         while let Some(p) = first_pkg_depending_on(pkg, &result) {
             result.push(p);