From 116ecaa63533dda55b393b5dad5fb504499b3f9a Mon Sep 17 00:00:00 2001
From: Aleksey Kladov <aleksey.kladov@gmail.com>
Date: Fri, 16 Mar 2018 12:29:54 +0300
Subject: [PATCH] Avoid intermediate vector

---
 src/cargo/core/resolver/mod.rs |  8 ++++----
 src/cargo/ops/resolve.rs       |  2 +-
 tests/testsuite/resolve.rs     | 11 +++++++++--
 3 files changed, 14 insertions(+), 7 deletions(-)

diff --git a/src/cargo/core/resolver/mod.rs b/src/cargo/core/resolver/mod.rs
index 9d765933a..e4f7483ac 100644
--- a/src/cargo/core/resolver/mod.rs
+++ b/src/cargo/core/resolver/mod.rs
@@ -416,7 +416,7 @@ pub fn resolve(
     summaries: &[(Summary, Method)],
     replacements: &[(PackageIdSpec, Dependency)],
     registry: &mut Registry,
-    try_to_use: &[&PackageId],
+    try_to_use: &HashSet<&PackageId>,
     config: Option<&Config>,
     print_warnings: bool,
 ) -> CargoResult<Resolve> {
@@ -662,7 +662,7 @@ impl ConflictReason {
 struct RegistryQueryer<'a> {
     registry: &'a mut (Registry + 'a),
     replacements: &'a [(PackageIdSpec, Dependency)],
-    try_to_use: HashSet<&'a PackageId>,
+    try_to_use: &'a HashSet<&'a PackageId>,
     // TODO: with nll the Rc can be removed
     cache: HashMap<Dependency, Rc<Vec<Candidate>>>,
 }
@@ -671,13 +671,13 @@ impl<'a> RegistryQueryer<'a> {
     fn new(
         registry: &'a mut Registry,
         replacements: &'a [(PackageIdSpec, Dependency)],
-        try_to_use: &'a [&'a PackageId],
+        try_to_use: &'a HashSet<&'a PackageId>,
     ) -> Self {
         RegistryQueryer {
             registry,
             replacements,
             cache: HashMap::new(),
-            try_to_use: try_to_use.iter().cloned().collect(),
+            try_to_use,
         }
     }
 
diff --git a/src/cargo/ops/resolve.rs b/src/cargo/ops/resolve.rs
index 618613964..e52e71de2 100644
--- a/src/cargo/ops/resolve.rs
+++ b/src/cargo/ops/resolve.rs
@@ -170,7 +170,7 @@ pub fn resolve_with_previous<'a, 'cfg>(
     // In the case where a previous instance of resolve is available, we
     // want to lock as many packages as possible to the previous version
     // without disturbing the graph structure.
-    let mut try_to_use = Vec::new();
+    let mut try_to_use = HashSet::new();
     if let Some(r) = previous {
         trace!("previous: {:?}", r);
         register_previous_locks(ws, registry, r, keep);
diff --git a/tests/testsuite/resolve.rs b/tests/testsuite/resolve.rs
index e991f9c05..2d99846d3 100644
--- a/tests/testsuite/resolve.rs
+++ b/tests/testsuite/resolve.rs
@@ -1,4 +1,4 @@
-use std::collections::BTreeMap;
+use std::collections::{BTreeMap, HashSet};
 
 use hamcrest::{assert_that, contains, is_not};
 
@@ -33,7 +33,14 @@ fn resolve(
     let mut registry = MyRegistry(registry);
     let summary = Summary::new(pkg.clone(), deps, BTreeMap::new(), None).unwrap();
     let method = Method::Everything;
-    let resolve = resolver::resolve(&[(summary, method)], &[], &mut registry, &[], None, false)?;
+    let resolve = resolver::resolve(
+        &[(summary, method)],
+        &[],
+        &mut registry,
+        &HashSet::new(),
+        None,
+        false,
+    )?;
     let res = resolve.iter().cloned().collect();
     Ok(res)
 }
-- 
2.30.2