Remove an unnecessary HashMap when Vec works

Dependencies aren't necessarily unique per name as the same dependency can show
up multiple times in various dependency kind lists, so it's not quite right to
use a hash map anyway.

Author: alexcrichton

src/cargo/core/resolver/mod.rs

@@ -182,7 +182,7 @@ fn activate(mut cx: Box<Context>,
 
     // Next, transform all dependencies into a list of possible candidates which
     // can satisfy that dependency.
-    let mut deps = try!(deps.into_iter().map(|(_dep_name, (dep, features))| {
+    let mut deps = try!(deps.into_iter().map(|(dep, features)| {
         let mut candidates = try!(registry.query(dep));
         // When we attempt versions for a package, we'll want to start at the
         // maximum version and work our way down.
@@ -430,8 +430,7 @@ fn compatible(a: &semver::Version, b: &semver::Version) -> bool {
 
 fn resolve_features<'a>(cx: &mut Context, parent: &'a Summary,
                         method: Method)
-                        -> CargoResult<HashMap<&'a str,
-                                               (&'a Dependency, Vec<String>)>> {
+                        -> CargoResult<Vec<(&'a Dependency, Vec<String>)>> {
     let dev_deps = match method {
         Method::Everything => true,
         Method::Required { dev_deps, .. } => dev_deps,
@@ -452,7 +451,7 @@ fn resolve_features<'a>(cx: &mut Context, parent: &'a Summary,
     });
 
     let (mut feature_deps, used_features) = try!(build_features(parent, method));
-    let mut ret = HashMap::new();
+    let mut ret = Vec::new();
 
     // Next, sanitize all requested features by whitelisting all the requested
     // features that correspond to optional dependencies
@@ -461,7 +460,7 @@ fn resolve_features<'a>(cx: &mut Context, parent: &'a Summary,
         if dep.is_optional() && !feature_deps.contains_key(dep.name()) {
             continue
         }
-        let mut base = feature_deps.remove(dep.name()).unwrap_or(vec![]);
+        let mut base = feature_deps.remove(dep.name()).unwrap_or(Vec::new());
         for feature in dep.features().iter() {
             base.push(feature.clone());
             if feature.contains("/") {
@@ -471,7 +470,7 @@ fn resolve_features<'a>(cx: &mut Context, parent: &'a Summary,
                                          feature)));
             }
         }
-        ret.insert(dep.name(), (dep, base));
+        ret.push((dep, base));
     }
 
     // All features can only point to optional dependencies, in which case they