parents can use a HashSet

Author: Eh2406

src/cargo/core/resolver/context.rs

@@ -1,6 +1,5 @@
 use std::collections::HashMap;
 use std::num::NonZeroU64;
-use std::rc::Rc;
 
 use anyhow::format_err;
 use log::debug;
@@ -35,7 +34,7 @@ pub struct Context {
 
     /// a way to look up for a package in activations what packages required it
     /// and all of the exact deps that it fulfilled.
-    pub parents: Graph<PackageId, Rc<Vec<Dependency>>>,
+    pub parents: Graph<PackageId, im_rc::HashSet<Dependency>>,
 }
 
 /// When backtracking it can be useful to know how far back to go.
@@ -265,14 +264,14 @@ impl Context {
             for (o, e) in self.parents.edges(i) {
                 let old_link = graph.link(*o, *i);
                 assert!(old_link.is_empty());
-                *old_link = e.to_vec();
+                *old_link = e.iter().cloned().collect();
             }
         }
         graph
     }
 }
 
-impl Graph<PackageId, Rc<Vec<Dependency>>> {
+impl Graph<PackageId, im_rc::HashSet<Dependency>> {
     pub fn parents_of(&self, p: PackageId) -> impl Iterator<Item = (PackageId, bool)> + '_ {
         self.edges(&p)
             .map(|(grand, d)| (*grand, d.iter().any(|x| x.is_public())))
@@ -338,7 +337,7 @@ impl PublicDependency {
         parent_pid: PackageId,
         is_public: bool,
         age: ContextAge,
-        parents: &Graph<PackageId, Rc<Vec<Dependency>>>,
+        parents: &Graph<PackageId, im_rc::HashSet<Dependency>>,
     ) {
         // one tricky part is that `candidate_pid` may already be active and
         // have public dependencies of its own. So we not only need to mark
@@ -383,7 +382,7 @@ impl PublicDependency {
         b_id: PackageId,
         parent: PackageId,
         is_public: bool,
-        parents: &Graph<PackageId, Rc<Vec<Dependency>>>,
+        parents: &Graph<PackageId, im_rc::HashSet<Dependency>>,
     ) -> Result<
         (),
         (

src/cargo/core/resolver/mod.rs

@@ -609,12 +609,10 @@ fn activate(
     cx.age += 1;
     if let Some((parent, dep)) = parent {
         let parent_pid = parent.package_id();
-        Rc::make_mut(
-            // add a edge from candidate to parent in the parents graph
-            cx.parents.link(candidate_pid, parent_pid),
-        )
+        // add a edge from candidate to parent in the parents graph
+        cx.parents.link(candidate_pid, parent_pid)
         // and associate dep with that edge
-        .push(dep.clone());
+        .insert(dep.clone());
         if let Some(public_dependency) = cx.public_dependency.as_mut() {
             public_dependency.add_edge(
                 candidate_pid,