change age to count edges not just activations

A pub dep conflict can be made by connecting two already activated pids

Author: Eh2406

src/cargo/core/resolver/context.rs

@@ -23,6 +23,7 @@ pub use super::resolve::Resolve;
 // possible.
 #[derive(Clone)]
 pub struct Context {
+    pub age: ContextAge,
     pub activations: Activations,
     /// list the features that are activated for each package
     pub resolve_features: im_rc::HashMap<PackageId, FeaturesSet>,
@@ -82,6 +83,7 @@ impl PackageId {
 impl Context {
     pub fn new(check_public_visible_dependencies: bool) -> Context {
         Context {
+            age: 0,
             resolve_features: im_rc::HashMap::new(),
             links: im_rc::HashMap::new(),
             public_dependency: if check_public_visible_dependencies {
@@ -108,7 +110,7 @@ impl Context {
         parent: Option<(&Summary, &Dependency)>,
     ) -> ActivateResult<bool> {
         let id = summary.package_id();
-        let age: ContextAge = self.age();
+        let age: ContextAge = self.age;
         match self.activations.entry(id.as_activations_key()) {
             im_rc::hashmap::Entry::Occupied(o) => {
                 debug_assert_eq!(
@@ -180,13 +182,6 @@ impl Context {
         })
     }
 
-    /// Returns the `ContextAge` of this `Context`.
-    /// For now we use (len of activations) as the age.
-    /// See the `ContextAge` docs for more details.
-    pub fn age(&self) -> ContextAge {
-        self.activations.len()
-    }
-
     /// If the package is active returns the `ContextAge` when it was added
     pub fn is_active(&self, id: PackageId) -> Option<ContextAge> {
         self.activations

src/cargo/core/resolver/mod.rs

@@ -218,7 +218,7 @@ fn activate_deps_loop(
         trace!(
             "{}[{}]>{} {} candidates",
             parent.name(),
-            cx.age(),
+            cx.age,
             dep.package_name(),
             candidates.len()
         );
@@ -264,7 +264,7 @@ fn activate_deps_loop(
                 trace!(
                     "{}[{}]>{} -- no candidates",
                     parent.name(),
-                    cx.age(),
+                    cx.age,
                     dep.package_name()
                 );
 
@@ -375,7 +375,7 @@ fn activate_deps_loop(
             trace!(
                 "{}[{}]>{} trying {}",
                 parent.name(),
-                cx.age(),
+                cx.age,
                 dep.package_name(),
                 candidate.version()
             );
@@ -525,7 +525,7 @@ fn activate_deps_loop(
                         trace!(
                             "{}[{}]>{} skipping {} ",
                             parent.name(),
-                            cx.age(),
+                            cx.age,
                             dep.package_name(),
                             pid.version()
                         );
@@ -594,6 +594,7 @@ fn activate(
     opts: ResolveOpts,
 ) -> ActivateResult<Option<(DepsFrame, Duration)>> {
     let candidate_pid = candidate.package_id();
+    cx.age += 1;
     if let Some((parent, dep)) = parent {
         let parent_pid = parent.package_id();
         Rc::make_mut(
@@ -947,7 +948,7 @@ fn find_candidate(
         // make any progress. As a result if we hit this condition we can
         // completely skip this backtrack frame and move on to the next.
         if let Some(age) = age {
-            if frame.context.age() > age {
+            if frame.context.age >= age {
                 trace!(
                     "{} = \"{}\" skip as not solving {}: {:?}",
                     frame.dep.package_name(),